# Overheated valves



## JustinRaney (Jun 1, 2018)

Is it possible for engine valves to overheat and become brittle? I had bought a car where they had left one fan blade off so it was running on one fan blade and also missing the air dam that catches air and pushes it thru the radiator when going down the highway. When i first got it would see temps up to 250 degrees but never blew a headgasket. I got the issue addressed as soon as i found this out after buying the car and runs at 198 degrees currently. I've put over 1000 miles on the car with no heating issues. I was curious as i was putting headers on the car i ran a magnet across the exhaust chamber of one of the cylinder heads and the magnet stuck to the valve pulling off a slight chunk of what seemed to be valve material as the magnet wont stick to aluminum heads. Is it possible for valves to become brittle from being overheated maybe and are the valves fully composed of the same material from valve stem to the combustion chamber part of the valve. From what i looked up there would be a hole in the valve if that was the case as i seen they burn thru mainly exhaust valves and on turbo engines. So is the whole exhaust valve composed of the same material? *martensitic steel with chrome and silicon alloys*, or a two-piece valve with a stainless steel head and martensitic steel stem. From what i've researched if it was a martensitic valve it would burn a hole in the head of the valve vs brittling the valve stem? Magnets don't stick to stainless steel so definetly not stainless steel but a steel valve. My guess would be maybe do a compression test on that one cylinder. Just curious if anyone's seen this type of issue. I was going to install a cam while replacing the factory 99 corvette balancer as it requires twice the work when you do go to install a cam. The balancer rubber is in pretty bad condition. I marked it months ago to see if it spins on the rubber. Other then that the car runs great i believe. It gets about 22 mpg when i check the cluster at hwy speed. I think fuel injected cars get better fuel mileage vs carbureted cammed cars.


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## Nut'n'Done (Nov 28, 2021)

Have you a picture of what pulled out of the chamber. Intake or exhaust?
Valves usually bend, aftermarket heads?
What engine are you working on?
On a side note,
You can pick up chineseium SS with a magnet.


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## lenaitch (Feb 10, 2014)

It's not uncommon for some engines to have baked-in design problems that result in either general or localized overheating problems.

Many stainless steel grades are magnetic:









Is Stainless Steel Magnetic? | Metal Supermarkets


There is a misconception that all stainless steels are not magnetic. In fact, there are some types and grades of stainless steels are magnetic.




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## FirebirdHank (Jan 31, 2021)

Exhaust valves take the highest temps produced in an internal combustion engine. Over heating as you described shouldn't have any effect on them. That piece om metal probably migrated from someplace else.


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## JustinRaney (Jun 1, 2018)

Thought id ask here as im doing about 510$ in cam upgrades and balancer upgrade to an elgin 220/224 112 .575 lift and some pac racing springs while doing a balancer swap after noticing the factory 22 year old rubber balancer has some bad rubber and may leave me stranded. Would hate for it to drop a valve shortly after or half a valve that'll damage the new cam i just put in. Higher spring rate and other labor done. If you ask me after looking at my buddies ported heads with a couple valves out of the head assembly if it were the stem it would be the size of 1/3 of a valve stem steel chunk the autozone extension magnet insisted on pulling out the exhuast chamber on an aluminum block/head ls1 engine. I may do a compression test on that one cylinder before installing the cam i believe they're suppose to be around 180psi.

Its an american ls1 engine at first wasn't too much of a problem i was repairing the factory exhaust manifold leak by switching to headers. I was just checking a couple exhaust chambers with the engine complete and in the car while looking to see if maybe i had dropped a bolt when the autzone extension magnet stuck to an exhaust valve on the drivers side 3 from the front pulling out what seemed like a gravel chunk. Hard to say if that would fall off into a cylinder or jam between a valve if the piece fell loose. After that i quit playing with the magnet. I should have kept it i threw it away disregarded it as i was just putting headers on my 99 corvette with 92k miles ls1 engine a few months ago. Supposedly theres a high temp setting that'll fuel cut if the engine is overheated on the c5 dtc or engine code list but not sure if my 99 c5 has this feature. I only ask as im about to do a cam upgrade with single beehives while changing the 22 year old factory balancer. Didn't think it be possible for a valve to turn brittle and drop with extra spring pressure and about 510$ in a cam/balancer swap. I wasn't too concerned at first as it is an internally stock 99 ls1 engine. I looked up valves with holes in them and the exhaust had burned straight through as if they were a one piece design that would only burn thru and not turn brittle. Just curious if you could run an engine at such a high temp for a long period of time not too blow a head gasket but cause exhaust valve issues, stress cracks, etc. I took a look at my friends aftermarket stainless steel valve either intake or exhaust ported factory heads and the magnet doesn't stick to one valve but does stick to the other on the aftermarket stock ported heads he had purchased. Theres reason they upgrade valves but i think it was to change the valve size i seen that they have titanium valves as well.


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## Nut'n'Done (Nov 28, 2021)

Given a possible overheat, detonation perhaps. I would be checking things out first.


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## JustinRaney (Jun 1, 2018)

would if compression check tests good? Im not too familiar with machinery i figured the combustion chambers get real hot too especially the exhaust valves worst case it would burn a seat or hole in the valve before brittling a valve stem? If a compression check tests good the motor should be fine and not require a head swap?


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## Nut'n'Done (Nov 28, 2021)

I would do a leak down test.


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## SPS-1 (Oct 21, 2008)

Justwayne said:


> Is it possible for engine valves to overheat and become brittle?


I am no expert, but certainly you can burn a valve. But I am not sure if saying "becomes brittle" is the best way to characterise it. I think its mostly just as simple as the edge of the valve can overheat and distort or melt a little. If anything, overheating it might anneal the material and make it softer rather than more brittle. Especially if you are modified, you could run lean and cause a problem. A compression check or leak down check should find it pretty easily.


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## JustinRaney (Jun 1, 2018)

A compression test is easiest for me my 98 ls1 z28 had around 180 psi i believe. So if it passes the compression test the valves should be fine? Im not familiar with doing the leak down test you would have to have the rocker arms removed and leak down tool and air compressor for the leak down test? Compression test should be easy enough before throwing the cam in and risk dropping a valve?


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## SPS-1 (Oct 21, 2008)

If that's a 99 engine, I would not be expecting factory compression numbers.
But al your cylinders should be showing pretty much equal compression. If some of your cylinders are showing different compression than others --- well, that is not good.

Lots of good information at CorvetteForum


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## Nut'n'Done (Nov 28, 2021)

Since we really don't know how well this engine has been maintained. Possible overheat, shrapnel in either intake/exhaust port etc.
It's your decision at this point.

If you feel the engine is healthy enough after a compression test and do not want to pull the heads.
Then throw the bump stick in, roll the dice and hope for the best at this point.
If your planning to do the cam, springs and balancer yourself.
I would take SPS-1 advice and check out the Corvette forum he suggested.
Have your compression #'s handy and try to do your homework, such as, what performance you are expecting to see after a cam swap and new headers.


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## Nut'n'Done (Nov 28, 2021)

If your looking for the best bang for your buck with more off line grunt and performance. I would look at a steeper rear gear before a bump stick, but that's just my opinion.

Then you have fuel mileage to take into consideration depending on how steep a rear gear you choose.


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## JustinRaney (Jun 1, 2018)

yes i post on the corvette forum as well but thought id ask a general question relating to all automobiles and the overheated of head valves and types of metal material and if anyone has heard of an engine completely dropping a valve totaling an engine or just end up with burnt valves low compression on a cylinder or cylinders.
Reason im doing the cam is part of regular maintenance in replacing the stock corvette balancer which has been known to walk off. I posted pictures i had whiteout marked it a few months ago to see if it spins on the rubber but as you can see the factory rubber is in bad shape.
The gear is 900$ installed with parts any ratio 3.73s, 3.90s or 4.10s. The used manual c5 3.42s sell for roughly 800$ on ebay. I already have the medium stage 1.75 elgin 220/224 112lsa .575 lift. I was thinking if i do a compression test and all test 180 then the valves or seats shouldn't have any problems. The first time i disregarded the valve chunk when i was installed 660$ headers as it was a stock motor which isn't worth much but by the time you have 450$ in new cam internals its not worth grenading or tearing up the brand new internals, cam and such on a bad engine or bad set of heads/valves. I can maybe try to find the 799 243 similar to the z06 heads for roughly 250$ and maybe mill them .020 to raise the compression and inspect the cylinders. The only problem is if the current heads on the car are good id rather use them as its a mild cam. I just put the new tsp headers on months ago shortly after i realized the torque tube couplers were trash and had to drop the headers and transmission to rebuild the torque tube with solid couplers. Got the car running again only to realize the stock balancer has bad rubber and on these cars you have to remove the rack and pinion so i was hoping to squeeze the cam/springs in with the balancer. I already have the cam, new stock size replacement balancer same as professional products. It is the auto 3250lbs performance axle package 3.15 gear not 2.73s like most of the auto ls1 cars.


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## SPS-1 (Oct 21, 2008)

Nice car.
Pulling the balancer is supposed to be lots of fun.


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## JustinRaney (Jun 1, 2018)

SPS-1 said:


> Nice car.
> Pulling the balancer is supposed to be lots of fun.


 It doesn't appear to be wobbling but as seen in pictures the rubber is in bad condition hate to be stranded when the balancer does walk off. Requires removal of the rack and pinion you can see the balancer is in bad shape im assuming the 22 year old factory balancer. The car reads 92k on the gauge cluster but no telling if they did swap engines or gauge cluster. I have an assault racing 7.5" that sells for 91$ from kmjperformance that is the same as the jegs professional products balancer arriving tomorrow. I noticed the balancer being in bad shape when i was changing the alternator decoupler pulley a real worn out pulley and regreasing the factory tensioner pulley. Sounded like it had alot of marbles under the hood. So hopefully with a compression test and maybe a leak down test with rockers removed the heads should be fine to use? I only have enough for the balancer, cam, springs, seals and pushrods but could maybe wait to change the heads to the 799 which are suppose to add 20hp.

The thing is i just got the car months ago and realized it needed a lower front radiator support and had broken exhaust manifold studs on both sides leaking exhaust. I pulled the radiator, bumper valve covers to do the headers and lower radiator support. A couple months later i realized the rattling was the torque tube couplers completely separated the input shaft from driveshaft. Had to drop the headers a second time for the torque tube and to replace the heads would require dropping the headers again.




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## SPS-1 (Oct 21, 2008)

Justwayne said:


> The thing is i just got the car months ago .....


Have you noticed yet they add 25% to the cost of parts just for adding the word "corvette" in front of it ?
I used to have a 98. 
Had every one of the common issues -- pull key wait 10 seconds, steering position sensor, gas gage suddenly going to zero, pass side targa top coating stripe, rocking seats, parking brake won't hold, balancer spun (2x), etc, etc


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## JustinRaney (Jun 1, 2018)

Yes the torque converters are twice as much as well as bunch of other stuff. Mine does the same pull key wait 10 seconds so i purchased an lcm5 which supposedly bypasses it but a few time after installing it did the same " pull key wait 10 seconds" and "steering column lock" at the local gas station leaving me stranded for 15 minutes before i could restart and drive off. Gas gauge does read off or will stay at the same level even when fueling supposedly techron additive or getting gas from cheron with techron already in it it suppose to fix the fuel gauge issue. I do got the driver seat rocks 1/2" when accelerating or coming to a stop. I haven't had the balancer issue yet but the rubber does look bad so i want to replace it with the aftermarket style that was the same price as a stock replacement balancer.


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## SPS-1 (Oct 21, 2008)

Piece of junk actually.
I bought the second year it was out. So you would think GM had time to fix most issues. No, the problems on 97's were also problems on 98's.... and 99's, .... and 2000's etc
I have not stepped foot in a GM dealership since that car.


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## Brainbucket (Mar 30, 2015)

As far as brittle valves, they would break off and destroy your engine. I went to school at a GM dealership on the LS1 cars in 2002. Nitrous will do that. Overheating won't as the engine will blow head gaskets before a valve will overheat. It's the combustion temps that overheat the valves and they are made for that. Now the cam swap. The valve and rocker have traveled the stock length. You extend the travel by cam swap will put both in new area. The valve and rocker have been moving thus far. Then new cam it extends the travel to an unused area. That how an engine may hurt itself. When I install a bigger cam, I pull the heads and rework them with new valve and rockers.


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## JustinRaney (Jun 1, 2018)

It is something that seems would only last the payment plan of the car._* You sure nitrous will do that? It is possible but I didn't see any signs of a n2o kit. The previous owner did have the cats deleted with straight pipe on stock manifolds and mentioned having put a replacement transmission in it.*_ So you think if it passes the compression test and leak down test that there shouldn't be anything wrong with the valves and something would happen to the head of a valve? Burnt? No compression? Before hurting the valve stem?


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## Brainbucket (Mar 30, 2015)

Should be fine. A burnt valve will show up in compression test and leak down test.


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## JustinRaney (Jun 1, 2018)

Yes ill try a compression test for sure have to rent the compression tester from autozone. One with a bad valve will show an unburnt or wet plug correct and 0 psi? The balancer came in today for 91.77$ stock corvette replacement. Waiting on pac-1219 springs and seals. I'll do a compression test before to figure out if it does maybe need a different head set. What i meant is aftermarket stock size 7.5" balancer. Wish they did manufacture underdrive pulleys for the same price. Thats where the mark-up is 180$-260$ for the ud pulleys.


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## SPS-1 (Oct 21, 2008)

I see a keyway in your balancer. Your crank doesn't have a keyseat, as far as I know.
Its probably common to other engines, so they stamp "stock corvette replacement" on it, and mark it up 25%.

Last I heard, GM was adding diamond grit to the bolt washer face, to try to grip the balancer better.


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## JustinRaney (Jun 1, 2018)

I think alot of aftermarket i may be mistaken like powerbond ud pulleys come with a keyway. I don't think it'll pose any problems once torqued? The stock replacement balancers are about the same price and the walking off is a common occurence. I was going to go with a speedmaster balancer bolt for 23$ about the same as arp. Is the keyway going to cause any problems. Its cheapest from assault racing 91.77$ directly is still kmj performance. I believe it to be the same as jegs professional products balancer that sells for 108$ or in the ebay ad from kmjperformance the balancer is 130$ but with free shipping. 

After looking all powerbond, trickflow or aftermarket balancers come with a keyway. Someone suggested to pin the crank but im not too familiar with doing that.


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## JustinRaney (Jun 1, 2018)

So you're saying do a compression test? There is no way for a piece of the upper valve stem to break off just leaving the valve head on with part stem? I'd hate for metal or parts of a valve to be riding around in the cylinder. I'm thinking of replacing the heads for a different set if the shortblock looks good it cylinder walls and piston tops. I'm waiting on some funds and then going to rent a compression tester for 40$ from AutoZone. I have put over 1000 miles since putting the headers on the engine and noticing that one valve flaw.
I do have an extra set of good 241 off a spun bearing 2004 gto ls1 engine the later ls1 heads but would cost the 50$ in head bolts and 50$ for head gaskets. Is it worth it to get a valve job from a local machine shop is is there not much in hp gains. I could maybe try to find the 799/243 heads locally for around 250$ they flow 250cfm around .550-.600 lift vs the 225cfm of the current or standard ls1 heads. Would be good for 20hp similar to the z06 or ls2 heads 400hp without the ls6 intake or sodium filled stainless steel valves bigger 4.00 ls2. The cam would add the 40hp with tune to make around maybe 440flywheel hp similar to the new 450hp c7 base model vette just not a 7 speed.


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## Nut'n'Done (Nov 28, 2021)

It's unfortunate that you didn't keep the piece you pulled from #5 cylinder.
If you put 1k miles since then you should be ok.

My thoughts would be a possible valve boss cracked at this point then.


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## JustinRaney (Jun 1, 2018)

Nut'n'Done said:


> It's unfortunate that you didn't keep the piece you pulled from #5 cylinder.
> If you put 1k miles since then you should be ok.
> 
> My thoughts would be a possible valve boss cracked at this point then.


You bet I should have hung onto it. I chalked it up as not a big issue as most cars i've dealt with that overheated had blown headgaskets where a simple head gasket repair would fix the issue on a 92 eclipse replaced the headgasket 2-3 times when i was 17 but always forgot to mill the head and would blow the head gasket again. I looked at a buddies older 706 ported heads with stainless steel valves i believe either intake or exhaust and the magnet wouldn't stick to them but the other valve either intake or exhaust they'd stick. If you ask me it was about the size of a gravel street pavement maybe the triangular part in the middle just on top of the valve head to stem. It was just a 2$ extendable autozone magnet i stuck in a couple ports playing around when replacing the headers wouldn't stick to the aluminum heads but did stick to the valve stem just inside the exhaust chamber took a second and drug across or around the valve pulling out what seemed to be a pavement sized chunk after sticking to the valve. I put the headers on 6 months ago and have driven the car across town and back no problems. I figured since it didn't blow a headgasket that maybe it was a common issue but never heard of it. I started looking into burnt valves on youtube as i was going to replace the cam while doing the balancer swap and seen a burnt valve usually melts a hole in it leaving zero compression and the plug wet. I guess ill try the compression tester to see compression first but maybe could pull the heads when doing the balancer and cam to inspect the pistons tops and cylinders. I've seen other lt1 engines that had grooves or lines up and down the piston bore. Another 95 lt1 z28 i had purchased as a good running car when i was 18 would sometimes smoke as there out the exhaust white antifreeze. Pulled the heads off of it and seen someone had been in there and replaced the gaskets with new fel-pro. Not sure if i ended up doing it twice but between the back chamber and water jacket there was a small nick that would leak antifreeze slowly. The car didn't overheat or anything but would burn antifreeze. I should have kept that piece of valve but even before i do maybe swap heads on this 99 ls1 would be a good idea to do a compression test as well as leak down test to confirm pistons rings are in good shape before proceeding to spend money on heads?

Since only the valve stem is exposed thru the exhaust ports you would think it have to be part of the valve stem no unless that valve was barely open or closed to where it would catch the lower part of valve stem on top of the valve head. Heres some videos directly after i found that out and was installing headers. This is how the car sits and drives currently as a daily driver. The stock cam is under .500 lift i believe and the replacement is .575. Man you bet would hate to tear up a new cam and or total the engine because of bad valve. Anyone ever heard of someone completely dropping a valve or halfing a valve wiping out an engine?


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## JustinRaney (Jun 1, 2018)

From looking at it the valve stem is pretty small it would have to be maybe part of this if thats possible but you would think the exhaust valve would then have a hole in it and not a complete valve? Has anyone ever heard of this and not completely burning a hole in the valve or completely burning a hole in the valve. Didn't look to have exhaust or black smoke on the material but what seemed a brittle but solid piece of the valve. Its possible it be the edge of the valve though i didn't notice any chamber piece to it. Is there a way to fit a small camera thru the spark plug hole? Looking at it could be the edge seat part of the valve but that would read low on compression? just curious if its possible for a valve to fall apart but still have the head of the valve and read good compression. I was sold the car missing one engine fan blade nut and an air dam that provides cooling to the radiator when going down the highway. I was completely unaware of this so basically sold a lemon soon as i got on the hwy noticed the temps would get up but was able to drive it 150+ miles at 241 degrees from where i purchased it according to the digital cluster gauge and would run cooler at lower speeds around 65 vs 80 as after getting it home noticed the cooling wasn't enough and seen the one fan blade was hanging in the radiator but luckily didn't blow a head gasket. No telling how long the previous owner ran it at those higher temps. Supposedly there is a fuel cut off when the car is overheated to protect the engine but not sure if my c5 is equipped with this.


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## Nut'n'Done (Nov 28, 2021)

Have a look at a cracked valve boss on the internet and let us know if you feel that could be the case. 
It is possible that you bent a valve slightly with over heating, that would cause the valve boss to crack and break off.

Unless your using NOS, I wouldn't be worried about holes in the valves or burnt valves at this point.

If it ran good for 1k miles after header install without burning a bit of oil on start up. No white smoke out the tail pipes on start up then you should be ok.

You will not see the valve stems looking through the intake/exhaust ports. I'm not sure what you mean with your last statement?


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## JustinRaney (Jun 1, 2018)

Nut'n'Done said:


> Have a look at a cracked valve boss on the internet and let us know if you feel that could be the case.
> It is possible that you bent a valve slightly with over heating, that would cause the valve boss to crack and break off.
> 
> Unless your using NOS, I wouldn't be worried about holes in the valves or burnt valves at this point.
> ...


I believe you can't see the exhaust valve stems thru the chambers with the engine in the car but should be able to feel around with a magnet which will stick to the stock steel valve stem thru the exhaust chambers. I need to do a compression test in the next few days but does it sound like it has fluttering its possible have a bad exhaust valve on the drivers side exhaust as corvette has a factory dual exhaust.


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## JustinRaney (Jun 1, 2018)

I rented a compression tester to test the current 99 853s that are on the car right now. I have a spare set of 241 heads off a ls1 engine that was run low on oil and had a spun crank bearings but i expect the heads to be in good shape. Its definetly part of the grey exhaust valve that came off on the magnet. I found a rock similar to the size of valve that either came off the stem or tringled top or even edge of the valve as i was removing the magnet on the 99 853 heads. The car runs in videos above. See pictures for what im referring to. Could clean these 241 heads up at machine shop and is it worth it for the valve job. One of my heads had a stripped rear intake bolt from the previous owner anyway. It would cost 50$ in gaskets and 50$ in bolts when doing the cam.


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## JustinRaney (Jun 1, 2018)

Ok heres that one plug or cylinder is indeed wet or has unburned oil around the edge while the rest are burned good. Im going to pull the 4 other plugs and run a compression test. What does this say that the exhaust valve is bad on this cylinder?


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## JustinRaney (Jun 1, 2018)

Well the one cylinder does test 150psi with the rest. The rental tool gauge would read off some times so took multiple attempts. Passenger front does read a little bit lower but i think its the gauge i may have got it to 150 psi or close i swapped cylinders once they read 150 psi or close. The passenger side plugs all looked clean just the one that had the starnge exhaust valve had some oil on the side. I swapped plugs with a clean one and will check it some other time. I did check my 98 z28 in 2011 compression test thought it was 180 psi but maybe it was closer to 160.


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## Nut'n'Done (Nov 28, 2021)

IMO, those readings are low.
I would do a wet test now.
Just put a teaspoon of oil in the cylinder and re-test each 1 when you get a chance, then give us the new numbers corresponding to each cylinder.


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## JustinRaney (Jun 1, 2018)

What are you saying the rings may be bad? I let it run to get up to temp and let it cool a bit pulled all the plugs as directed by the compression test tool i rented and cranked 3-4 turns each cylinder read the same. I thought that was a bit low as well. It is the autozone loan a tool compression tester. Is the oil test to see if the rings are maybe wore or for a fully cycling engine with oil splashed up in the cylinder bores. The only thing that makes me worry is the intakes on these cars are directly in between the hood and bumper. Almost all of them i seen. I read somewhere you can put a hood seak to prevent rain from getting on the filters. A really bad design holley makes an intech filter set-up with what looks like rain covers. The stock corvette intake has a small opening and they recommend running an open filter with the top of the intake box off for 15 hp but leaves it susceptible to rain. From the factory i dont believe they come with a hood seal but maybe.


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## JustinRaney (Jun 1, 2018)

I seen another guy with a built ls1 on another forum read 150 psi as well and it read higher 180+ with the other compression gauge it may be the autozone rental tool. It is made by "OEM TOOLS" tools for professionals.


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## JustinRaney (Jun 1, 2018)

Nut'n'Done said:


> IMO, those readings are low.
> I would do a wet test now.
> Just put a teaspoon of oil in the cylinder and re-test each 1 when you get a chance, then give us the new numbers corresponding to each cylinder.


I tested one cylinder with a good amount of oil few tablespoons like when rebuilding a new motor and installing pistons and the cylinder pressure didn't change. It still reads 150 or just above 155 maybe psi as it read before without any oil. This would mean the rings are good and maybe the compression tester is a bit off? Its the 40$ tool you can rent or keep from autozone. I searched some threads where this happened as long as they were in the same range the compression testers sometimes read off. I did notice however i tried the cylinder i swapped the dirty plug too and the plug came out clean so im not sure why that one plug gets oil on it from the one cylinder that had the exhaust valve issue.

You may be right if the shortblock is good and that one head doesnt drop that valve before i get to installing the balancer and cam ill maybe swap a good set of heads and have them checked at the machine shop. I may be able to save up for some 250$ 799 heads that flow 250-260cfm vs 225-230 cfm of the stock 853 ls1 heads.


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## Nut'n'Done (Nov 28, 2021)

Why did you put several tablespoons of oil ?
You will get a false reading.
Just use 1 teaspoon.

Your all over the place here.
We can help you but you need to focus on diagnosing the engine 1st before you get carried away with thinking 40hp with the cam 20hp with CAI etc.


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## JustinRaney (Jun 1, 2018)

Dam dude i got the same reading with and without the oil lol. I used a small syringe it ain't going to hurt anything. I think its the compression tester have another car ls1 can test it on with higher mileage bearings, rings. I think its this specific compression tool. I was told as long as they test within the same range and all were within 150psi.

My comment with possibly low compression psi on an ls1 corvette engine being due to the air filter placement and its susceptible to being dusted on rained on easily but others state the hood seal prevents that.


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## Nut'n'Done (Nov 28, 2021)

If they all remain close to the same then I would say your timing is off.
That's not a bad thing at the moment.
Can you set the timing properly?


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## JustinRaney (Jun 1, 2018)

Nut'n'Done said:


> If they all remain close to the same then I would say your timing is off.
> That's not a bad thing at the moment.
> Can you set the timing properly?


Set the timing? Its a dot to dot timing chain on a fuel injected with stock 22 max timing thru ecm i believe on a ls1 engine. You mean maybe a timing chain wore out all mine read 150psi is a stock 99 ls1 engine with headers. A buddies gto with 155k mile longblock and a big 228/232 112 lsa cam, new timing chain pushes 180 psi on all cylinder with the same compression tool. His has slower pumps on the gauge but eventually pushes up to 180psi with a big cam. I'll try again on my 99 stock ls1 see why it has 150 psi on all cylinders that i dont know why.


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## Nut'n'Done (Nov 28, 2021)

Do yourself a favor here.
Look up dry/wet compression test along with verifying timing since your balancer has no factory marks.


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## JustinRaney (Jun 1, 2018)

Well its hard to say at 8am this morning i pulled all the plugs had started and moved the car to driveway area to work on. I tested all 8 cylinders a couple times to be sure and all were within a few psi of 150. Just now after someone else tested 180 with a bigger cam and new timing chain i went ahead and tested my 99 corvette two plugs that had tested 150 earlier and read 165 and 160 psi consistently given enough cranking. Its hard to say if maybe im using the tool incorrectly but ideally with the same operater with all 8 at 150 psi this morning with no plugs and just a inj,fuel pump, ign fuses pulled and 2 plugs removed testing above 165 psi this eveing. Could be operator error. Not sure why it would fluctuate the tool kit said turn the engine over 3-4 times maybe not enough times or the hose not tight enough to the engine head. I think the engine should be good given that data. Now the one cylinder i did add a small amount of oil too still read 150 psi as before without oil.


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## JustinRaney (Jun 1, 2018)

I'll have to try it again sometime next time i have the tool available. I was mainly checking to see if that one cylinder maybe had a bad valve but from all readings 150 psi this morning and 150psi on one even with the oil. Not sure if it was operator error with the tool but did do a couple real quick before returning the tool to autozone as they close at 7:45pm christmas eve the two i did check were within equal range of 165psi. Im not sure why they changed in compression.


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## Nut'n'Done (Nov 28, 2021)

That is why I suggested a leakdown test initially. Do it once and done.


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## JustinRaney (Jun 1, 2018)

Now for the leakdown test it will require a different tool rental. You just loosen all the rocker arms so the valves can close and supply pressure via the air compressor thru the dual gauge and regulator? Is this going to be more informative on valve seats or rings or both?


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## JustinRaney (Jun 1, 2018)

you think a borescope would get a better view of the cylinders and valve chambers thru the spark plug hole? A picture i found on the internet but curious if the autozone loan a tool borescope would allow for this kind of view.OEMTOOLS 2.4in Color LCD Screen Borescope (autozone.com)


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## Nut'n'Done (Nov 28, 2021)

The leakdown test will certainly nail down what the problem is.
Be it valve, seats, rings, head gasket.
This engine is new to you ( possible lemon you say)
We know nothing about this engine really.

We are only going on what you mention here.
You added flutter, which could be timing, bad tune etc.

The plugs are a good indication something is wrong with more than 1 cylinder without going into detail on Christmas eve.


It would have helped to know what plug came out of what cylinder in relationship to the tested cylinders.

I would expect to see 140-150 in a 8:5:1 with 100k miles

I would expect to see 180-190 in a 10:2:1 with 100k miles 

You didn't mention a tune after the headers or previous work performed.

Take your time, clear the cylinders out now since we don't know how much oil you used on the wet test.

You will be much further ahead if you do some searching on performing a leakdown test properly. Lots of info on the web.

Enjoy the holidays and be safe.


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## JustinRaney (Jun 1, 2018)

Now it is possible as it is a rebuilt title with 92k that was wrecked upfront they did they did swap some drivetrain parts but im unsure if a cluster swap or pcm is how you go about changing the miles if someone were to do that. I did check they are 853 heads for 99 and the ls1 corvette intake which doesnt have egr from the factory. It has the factory glove box Gu codes jet black interior and performance axle package with 3:15 gear. Everything lines up as far as alignment and rear cradle bolts stabbed perfect on a fixed drivetrain which is what i was afraid of when repairing the torque tube couplers and reinstalling the trans. I've heard of late 70s sbc iron heads cracking or having cracks due to thinner castings im not so sure on aluminum or the valves of 99 ls1 engines comparing iron to aluminum. Now to do the leakdown test id have to purchase the correct tool from harbor freight i believe is the cheapest for 25$ since none of the auto parts stores carry have the tool for rent. I was thinking of getting a set of fel-pro permatorque head gaskets and swapping a different set of heads when doing the cam it will just require removal on the intake and headers and will allow to do inspection the the piston tops as well as cylinders. There isn't any piston slap from what i can tell and the car doesn't smoke or burn any oil though that on one cylinder with the bad or brittle valve stem up into the exhaust port maybe has a bad valve seal is the only way i can think oil would make it onto the spark plug.

That extension magnet when fishing in the first two cylinders stuck to the 3rd back drivers side and meanuevered a circle or half circle as the magnet was stuck lightly to the valve. Hard to say as i think it would blow any metal chunks out the exhaust port but that isnt good.The only wet oil plug is that cylinder that the magnet had pulled off what looked like half a valve stem or top off the valve thru the combustion chambers but did test equal 150 psi on all 8 i swapped that plug with the one next to it and the same plug came out dry. That is strange as i got about 165 psi and 162psi on a couple 7-8 hours later by just pulling the plugs on those two cylinders without any oil or other test variables before returning the tool. Not sure what would alter the compression numbers in terms of engine up to temp or car thats been sitting for hours. One thing i did discover is my plug wires were in bad shape and need to pick-up a new set from the autoparts store

Its a 99 corvette ls1 4l60e 3.15s factory gears. The previous owner mentioned having just replaced the transmission with a used one and the car was running good bring a mechanic to inspect it with me at his place of work. After seeing the car he told me the exhaust manifold i figured couple broken exhaust bolts in the head " that back ones stripped in the back of the manifold causing an exhaust leak" and "replaced one door" and that he " just replaced the water pump". Took it for a low speed test drive and a few minutes on the highway didnt notice anything. About 15 minutes after purchasing at 70mph 170+ miles away the car would get up to 240+ degrees at higher speeds and the alignment was way off the car would pull to each side of the lane unless the wheel was held tight. At slower speeds 65 mph vs 75mph or so i noticed it ran cooler 239-241 degrees and got the car back home. Inspected it halfway at the gas station and car was running fine. I know a little bit about mechanics. the car was stock besides a dual cone air intake and the cat converters removed in place of straight pipe.

The car was lowered 1"-1.5" so i couldnt see that it was missing the front air dam that forces air up into the radiator when going down the highway. After getting it home I removed the front radiator and found that one fan blade nut was missing and the fan blade was hanging there causing the car to overheat running only one side fan. Had an extra ls1 cooling fan reverse thread nut and reinstalled the second fan and began replacing a new lower radiator support as his was in bad shape and new cooling air dam on the bottom of the car as well as headers to repair the exhaust leak. From what someone told me the cooling fans don't come on till 235 degrees the high speed i believe and turn off at 219 degrees. Mine is bypassed with relays and the cooling fans turn on when the key is turned on and the car always runs at 198 degrees currently. Oil pressure starts 60 and goes down to 40 psi when cruising and down to 20 psi at 600 rpms with fully hot oil or maybe an hour or two of driving as i've tested this thing across town. Has all new fluids as regular maintenance with new bosch platinum plugs. He had mentioned putting a new transmission in but its hard to tell if he sold it as a lemon as i noticed a bunch of rattling that was linked back to the torque tube and rotten rubber couplers with the driveshaft weights broken off and a couple bolts that hold the input shaft to the driveshaft thru the coupler. Upon pulling out the torque tube there wasn't any markings on the transmission but the torque tube itself had marker writings on it as if someone replaced it with a used one with torn couplers or premeditated selling an advertised good one with bad rocket man couplers. The front flexplate that attaches to the engine had Y markings under the flywheel inspection cover that looked like someone had been in there before. Only way to mark it would been turn the engine over to access and mark all flywheel studs or have had the torque tube completely out with front bellhousing and make it look like someone did repair work to it.

In this current time the car runs great or is set-up to drive across town no issues just need to replace some bad spark plug wires that got damaged when doing the compression test and that strange exhaust valve cylinder head issue sometimes has me wondering. After replacing plug wires ill figure out how to get a tool to do a leakdown test on the current engine. It really is hard to say as the small amount of oil trick in one cylinder didn't alter compression one bit and later on the day vs morning with alot of condensation on the the hood and other then starting the car to move it to a better driveway position to perform the compression test. Has anyone done a compression test in the morning with alot of condensation or water on the car with different results as this could have had a bit of moisture in the cylinders. The car did smoke like normal from the morning car start-up that takes 15 -20 minutes or even all morning to clear up. The car maybe ran for 10 minutes not quite up to engine temp as it takes ahwile to heat up the oil as well before performing the compression test. Hard to say as i did have to let the headers cool off before working with the compression gauge.


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## JustinRaney (Jun 1, 2018)

Replaced the spark plug wires today with a new duralast set. The car runs good otherwise. I'll peform a leakdown test later on when i have the funds to purchase the 25$ tool from harbor freight or amazon. How can you tell if they swapped cluster or ecm or even the motor to change the miles as the car is a rebuilt title. Says 92k on the odometer original jet black interior which seats have been reupholstered and ls1 corvette intake no egr, 853 99 head casting number. Though maybe when doing the cam it would be nice to find a newer 853 set or 799 head set for 250$ to have checked at a machine shop for straightness or even a light resurfacing .005 but would have to measure with a caliper as too much mill alters pushrod length and permatorque fel pro gasket set. I did do the compression test early in the morning with about that much condensation on the windshield and/or engine exhaust. Not sure if that makes a difference in low reading compression numbers vs later in the day.


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## JustinRaney (Jun 1, 2018)

I believe the exhaust flutter is normal for the factory h-pipe corvette dual exhaust as the h-pipe has smaller holes maybe 1" vs 2.5".
Well when doing the cam i was going to pull the heads if these are the correct replacement valves wouldnt hurt to replace all 16 Stock Exhaust & Intake Valves Set for 1997-2005 Chevrolet Gen III LS Engines | eBay Have the machine shop lap them. How much should you expect to pay for them fit stock size valves? Both are 8mm 1.55" exhaust 2.00 intake. This should keep worry free after putting a cam in.


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## Nut'n'Done (Nov 28, 2021)

It has been some time since I sent a pair of heads out. IIRC, I paid around $800 CDN in 2016 
I wouldn't trust Ebay/amazon valves/parts but that's just me. If you choose to buy them, I would mic them and check with an indicator for runout myself. I either use Performance Improvements in Canada, Summit or Jegs. 
I doubt very much that any reputable machine shop will install them for you. 
What current codes is the engine throwing at you? Have you checked that?


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## JustinRaney (Jun 1, 2018)

I found a set or each valve stocking melling valve replacements from summit or rock auto has them. Its hard to say if even a amachine shop can check them. They want roughly 250$+ for a regular valve job or 95$ to simply diagnose dissaessmble a set of heads with the current valves stated they didn't lap valves but had to grind them on a valve job. One place told me if you dissassemble and number the valves correct order he'd clean them for 40$ and pressure check for cracks is 125$ i believe for the pair or both aluminum heads. The only codes i have are for the hvac and p0410 p0140 p0160 for the air pump and rear o2s i deleted with headers. Those can be tuned out. Yes summit and rock auto have the melling stock replacement valves not replacing them i guess would take all 16 valves or new set someone on ebay had new take outs stock valves for 75$ for all 16 valves refaced whichever that means but if they're included in the valve job i guess sure. Some other people stated it be better to get a different set of 799 or 243 a better flowing set of heads for 250$ just not sure on just having them resurfaced is expensive but i think may be included in the valve job.


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## Nut'n'Done (Nov 28, 2021)

Some other people stated it be better to get a different set of 799 or 243 a better flowing set of heads for 250$ just not sure on just having them resurfaced is expensive but i think may be included in the valve job. 


What are your goals for this car. Will this be more highway driven or mostly town/city driven. 
If it were me, I would pull the heads and see what you have to work with.
IMO, you only have 3 options really. Cheap, fast, or reliable. You can't have all 3


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## JustinRaney (Jun 1, 2018)

Im good with cars had a 66 fairlane 4 speed daily driver, 95 z28 lt1 6 speed, and a 98 z28 6 speed with a s475 turbo all daily drivers all at different times and a 2001 escort zx2 from 17-23 someone had rear ended in feb 2017 when i was 27 causing alot of injuries. The thing i've never had is an auto performance vehicle which i found out the hard way the manuals are faster and stronger transmissions with clutch but i had suffered a snapped left arm injury from the wreck leaving me to buy an auto v8 ls1 daily driver a few months ago. Yes i think pulling the heads and atleast i believe you can remove the valves yourself to inspect with brakekleen as the car runs good now with current heads if you number the valves and put them in correct order they came from removing valve or valves to inspect them shouldn't be a problem from what the machine shop told me. I've changed springs before with dual springs and new seals with heads on the car. Its daily driver not sure how long i plan to keep the car but doing the balancer and small cam as a regular maintenance.


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## Nut'n'Done (Nov 28, 2021)

Being good around cars is a plus. I agree, number everything and place in zip lock. Can't go wrong that way. 
Sounds like you have a good plan for the car. 
Good luck!


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## JustinRaney (Jun 1, 2018)

Ok well installing a cam and replacing the balancer on the car with an aftermarket and replacement front seal set. Heres how far i got. Have the balancer removed you can see the original front cover seal broke off and wore a groove into it pretty bad. I have a new front cover seal set and replacement balancer im going to be installing with the cam. I think im going to reuse the stock timing chain and oil pump. After installing cam and balancer i need to decide if im going to use the current heads or swap a set of the later 241 engine heads i have sitting here that are in good condition with the pac 1219 spring set and new seals. I already have head gaskets so wouldnt hurt to pull the one or both engine heads and inspect the cylinders/piston tops for any damage as well as take a take a better look at that valve. Would anyone happen to know if 591220 is an aftermarket replacement balancer or stock gm for 99 corvette. Its wore pretty bad and the seal is messed up so have the replacement parts here.


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## JustinRaney (Jun 1, 2018)

I didnt see anything wrong with the valves with the headers off im probably going to leave the heads alone and use them as is there really isnt any signs and i cant find a groove in any. Im just going to change the balancer replace the front seal which was bad and new valve seals and springs.


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## HotRodx10 (Aug 24, 2017)

Not sure where you are, Justwayne, but one note about 'low' compression - compression readings vary by the elevation above sea level. The same engine that measures 170 psi at sea level will read about 145 psi at 4000 ft.


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## JustinRaney (Jun 1, 2018)

Its hard to say the car does have a rebuilt title from a front end collision so i would be suspecting if they had swapped a high mileage motor or something when the car was wrecked back in 2009 i think it was. It does have a replaced rack and pinion with a date of 2009. From what i can tell the motor is original to the car or a lower mileage motor. When swapping the cam i noticed the ls1 thrust plate didn't have much wear on it. I have another cam thrust plate from my 98 z28 that blew up at the dragstrip with maybe 550whp 9lbs s475 turbo that does have heavy wear on it from. Its hard to say if the 250hp extra from a stock ls1 would make any difference on cam thrust plate wear. 

I purchasd a better intake filter that sits behind the hood and bumper where no rain can access it. The c5s have a bad design where the intake or air filter sits that make it prone to rain water. I bought a hood seal but theres no telling hong it was ran that way with the possibility of getting dirty water or dirt thru the filter and into the engine.

All were 150psi but right before returning the tool i checked 2 cylinders that were up in the 165psi 162psi how the compression changes up to a higher range from a hot or cold car i have no idea.
I did get the car running with a new balancer and the cam hopefully all is well and its a nice daily driver. I still need to have it tuned for the cam and thats about the last mod for it i think besides maybe a varam air bridge and better mufflers to get some sound out of it. I've driven the car maybe 80 miles locally with the stock cam no WOT as it needs a tune the o2s will calculate stoich 14.7afr and maf sensor can read up to 4k rpms.

I may do a leakdown test or another compression test at a later date after replacing the dual cone filters susceptible to rain to a new oval air filter as im not sure how old the current filters are. Someone elses similar ls1 engine tested 180 psi on all 8 cylinders thats when i checked the two on my 99 c5 and seen the compression had went up. Was suspecting maybe a 200k mile+ ls1 but how you get worn out rings im not too sure. I bought the car stock other then the dual cone air filters and cats deleted off the factory exhaust. I did the oil trick and no change in compression on the one i tested so i dont think the rings are worn on but ill try it again at another time. Its possibly someone had put a n2o kit on it and wore the engine out that way then removed it sold me the car.

Got the car running hopefully all is well i didn't seen anything wrong with the certain valve i suspected or any of the other ones but i do take it easy on the car vs WOT or 1/4 mile passes. Thought with that being said hopefully there aren't engine issues that will arrise.


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## JustinRaney (Jun 1, 2018)

I drove it maybe 70 miles to confirm the camshaft install went alrite and to see if the car surged before maybe taking it to a local dynotune shop or mail order tune. A mail order tuner told me the maf calculates air flow up to 4k and would go lean above that and that the o2s would read the afr putting it at stoich as long as its kept at lower rpms and low throttle until i have it tuned. Im going to have the car tuned for the cam and headers but does indeed idle,run and drive with the small cam on the Auto c5. When i first started it would idle but when revved stahl out once letting it idle a few heat cycles the car started idling fine and revving fine without stahling out so i took it up to the gas station.

This is it after replacing the new balancer which are known to walk off on the c5s, comp valve seals, pac 1219 springs, tsp 7.4 pushrods and new front seal that was tore up and wore a groove on the stock aluminum balancer hub. Hopefully there isn't any damage to the engine regards into the thread title that would tear up 700$ in new balancer, cam swap parts plus total the factory ls1 corvette engine. I did drive the car part throttle 50 miles locally to confirm the car wouldn't surge and cam swap went correct and no knock or valvetrain noise appear and to maybe heat cycle the new single beehive springs kept under 1/4 throttle and lower rpms. Either way would still probably have to drive it to a local tune shop but i may just go with a professional mail order tune.


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