# My son the gear-head.



## Bud Cline (Mar 12, 2006)

My seventeen year old son has a 91 GMC 4X4, 350.

He has disassembled the engine to find some of the rod/crank bearings have worn and spun and in some cases stacked.

He's down to the bare block.

Obviously it needs new bearings and the crank turned. This also means it also will require new connecting rods.

Pulled down the topside...of course the cylinders are worn but not seriously and could be honed.

My question is...
Is it worth it for us to replace and rebuild all of the worn parts or would a reman be the wiser thing to do?

A crate engine is out of the question for now and a used engine may just present us with more of the same problems he has now.

So...what to do?


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## rustyjames (Jul 20, 2008)

If a main bearing spun it'll the block will need to line bored which will add to the cost. You might want to think putting in a used engine, I've bought cars/trucks just for the engine, and 350's are pretty easy to come by.


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## Bud Cline (Mar 12, 2006)

Rod bearings spun and two stacked. Crank bearings were in-tact but obviously worn.

Just not sure it is worth the labor (and time) to do it ourselves but he of course wants the experience.


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## BigJim (Sep 2, 2008)

Bud, look on the first counter weight or in that area to see if the crank has been turned before, or you could have the grinder mic it to see if it can be turned again. I don't know if they sell crank kits today or not but you would still have to have your rods worked or buy reconditioned. But then if you did you would have to have the wrist pins pressed.

You might check out a wrecked truck and check the miles, you might come out ahead buying a used engine.


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## Windows on Wash (Aug 30, 2011)

Get an engine rebuild kit and a good machine shop.

If he blows it up, you won't have that much in it. You can buy a cast crank pretty cheaply. 

If you want to go higher HP, buy a crate motor.


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## cjm94 (Sep 25, 2011)

Yes a good machine shop can recondition your block pretty reasonably. Rebuild kits for Chevy 350's are cheap


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## Windows on Wash (Aug 30, 2011)

Only "X" factor is the crank as mentioned above. Depending on how bad it was and what kind of HP he wants to make, they may or may not be able to grind it.


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## cjm94 (Sep 25, 2011)

Windows on Wash said:


> Only "X" factor is the crank as mentioned above. Depending on how bad it was and what kind of HP he wants to make, they may or may not be able to grind it.


Agreed. But a machine shop can probably find you a used crank if it is to far gone. May even have some stock ones laying around if they do performance engines.


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## BigJim (Sep 2, 2008)

Just a quick check to see if your crank is cracked or not, hold the crank by the first counter weight and tap it to the floor (concrete) if it rings it is good, if it thuds it is cracked. Some times when a rod or main bearing is spun the crank will crack.

You might want to check out the cam while you are at it also the cam bearings. Check the edge of the lifters also, if they are sharp they need replacing.

Bud did your son number the rods and pistons, they have to go back in the same hole. Not trying to be a smart butt, just don't know how much he knows about rebuilding an engine.


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## Bud Cline (Mar 12, 2006)

BigJim said:


> Just a quick check to see if your crank is cracked or not, hold the crank by the first counter weight and tap it to the floor (concrete) if it rings it is good, if it thuds it is cracked. Some times when a rod or main bearing is spun the crank will crack.
> 
> You might want to check out the cam while you are at it also the cam bearings. Check the edge of the lifters also, if they are sharp they need replacing.
> 
> Bud did your son number the rods and pistons, they have to go back in the same hole. Not trying to be a smart butt, just don't know how much he knows about rebuilding an engine.


I'm trying to get him to understand that if there is enough wear on the rod-bearings to spin and stack a few bearings then the wear is throughout the engine. I mentioned the cam shaft (which looks pretty good actually) and I told him there is likely plenty of wear on the valves and lifters and springs, etc. So to do this right, would be a complete overhaul of all of the friction points. 

As much as I enjoy seeing him take this engine down bolt by bolt, I'm not sure it is wise for him (us) to try to reassemble this thing. I have no doubt he can do it but this is a lot of work. What happens when it all goes back together and it doesn't run, or doesn't run properly? Holy Crap!!!! Not sure I want to do this again anytime soon.

It's been a few decades since I have been inside of one these engines. It was fun back then but now I'm not having that much fun with all of this.


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## BigJim (Sep 2, 2008)

I always hated the clean up, scraping the old gaskets off, cleaning the ring grooves, washing the gunk off, especially cleaning the ring grooves. Things change and I am sure they have since I did mechanic work back in the 60s. Back then you could get a rebuild kit with reworked rods, new pistons, crank kit and all the gaskets fairly reasonable, I don't have a clue about how that is today.

If I were in your shoes I would go with a different engine, if it had that much wear on it and spun bearings there is bound to be metal in the engine that will need to come out and unless you have a pressure washer it may be a little hard to get all of that out.

You will need a new oil pump and screen, it is really hard to get all the shavings out of the pickup tube.

If you do put new rings in you will need to hone the cylinders so the new rings will seat, actually if you use the old rings you will need to hone and if you are using the old rings the grooves weren't cleaned so you will have problems.

The lifters will need replacing or they must be reinstalled back in the same hole they came out of, if not there is a good chance they will eat a cam lobe off.

The rod caps must go back on the same rods and the spit hole goes toward the cam, the notch on the pistons go toward the front of the block. Can't believe I remember all that.LOL

One more thing, when you get the engine back together, use non-detergent oil for break in or the rings will not seat right.


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## beenthere (Oct 11, 2008)

Bud Cline said:


> It's been a few decades since I have been inside of one these engines. It was fun back then but now I'm not having that much fun with all of this.



But he is, and that may be what counts.


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## Bud Cline (Mar 12, 2006)

beenthere said:


> But he is, and that may be what counts.



THAT is exactly what it is all about!

Next year, (his Senior year in high school) he is taking a class that will allow him to totally rebuild an engine IF he has one. Well the way I see it, he may have one. In the meantime we'll get another one to get him back on the road as soon as possible. The carcass he has now has a core-value of $100. Seems to me we should keep that engine for next year and consider forgoing the core-value as an investment in his future school activities.

He has excelled in Machine Shop and can pass any Welding certification they could throw at him. He's been a participant in Skills U.S.A. for three years and has been to a couple of State Finals in the Skills U.S.A. competitions.

The kid loves this crap, as I did when I was his age.

I remember the first 327ci I rebuilt. Put it together, re-installed it, turned the key, and I'll be damned if it didn't crank-over almost immediately. Hell I think I spent the next week just running it and tweaking it, and revving it without the muffler. I Loved it! Can't say the same for the neighbors.


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## BigJim (Sep 2, 2008)

Bud Cline said:


> THAT is exactly what it is all about!
> 
> Next year, (his Senior year in high school) he is taking a class that will allow him to totally rebuild an engine IF he has one. Well the way I see it, he may have one. In the meantime we'll get another one to get him back on the road as soon as possible. The carcass he has now has a core-value of $100. Seems to me we should keep that engine for next year and consider forgoing the core-value as an investment in his future school activities.
> 
> ...


That is great that he has taken an interest in those skills, most kids now days want the computer jobs but there will only be so many of those to go around. The skills he is learning will always be in demand.

Man, that 327 was my favorite engine also the 427, they both were some mean machines. I had one 327 with popup pistons 13:1 and a mean bump stick, that was a bad one, had it in a 62 Chevy II convertible. It was fun to fit in there because they didn't come out with V8s in a Chevy II until 65. OK I will shut up now, got a little wound up there.


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## Windows on Wash (Aug 30, 2011)

Ah...13:1.

Can't do that anymore on pump. Leaded gas was good stuff.


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## BigJim (Sep 2, 2008)

You are right, you would have to buy your gas at the airport and run a water injector to keep the ping down since there is no lead anymore. Then the metal in the newer engines wouldn't handle it.


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## Bud Cline (Mar 12, 2006)

Okay...exploring all avenues...

In calling around to locate and price a used-engine I am being asked if our engine is a "two-bolt" or a "four-bolt" engine.

What the hell is that all about and why do I care?

I have located a couple of trucks with bad trannys but running engines. So...what do I know about these trucks as far as 2-bolt/4-bolt?

hehehe: my spell-check doesn't like the word "tranny".


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## BigJim (Sep 2, 2008)

You already have the oil pan off, look at the main caps, do they have two bolts holding the caps to the block or four bolts. A 4 bolt is better because mostly they are made for hard pulling trucks. A 4 bolt main will usually cost a little more than a two bolt.

I would look for a truck that has been wrecked because you know it was running when taken out of commission. Just my thinking is if just the tranny is shot and they want to sell the motor chances are the motor wasn't worth putting another tranny behind it.

First thing is check the oil dip stick and see if it smells burned, and if the oil is in really bad shape. If you can find a truck that has low miles on it the engine should be in pretty good shape. See if they will let you pop the pan and see how much metal shavings there are If possible check how much sludge is under the intake. If they have run Quaker State oil walk away, you will have to chisel the sludge out of the valley.

If you can see the crank, look at the first counter weight at the front of the block, if the crank has been turned it will be stamped how much they took off the mains and rod journals.

If the heads are off look at the top of the pistons, if there is a number stamped there, then the engine has been rebuilt, if the stamp is .060 the engine can not be bored again, I personally wouldn't want one over .030 because you may be able to have it bored again but not with .060.

Check to see if the freeze plugs are in good shape and aren't cracked between them. Especially check the rear plug to see if the cam has run back and bumped it.

See if you can move the crank back and forth, it shouldn't have much slack in it, if it does the mains are shot. If the heads are off, check the narrow place between the cylinders to see if there are any cracks there. If the heads are on, look at the exhaust ports to see if there is any oil, if so the engine is burning oil or the valve guides are worn on the intake valve. If they are a creamy brown or gray, that is a good sign. 

Be sure to check to see if the motor had a automatic tranny or a stick bolted to it, if you buy a motor that had a stick you will have to pop the pilot shaft bushing out or the torque converter won't bolt tight to the flywheel and it will crack later on. 

To get the bushing out, if you need to, stuff wet toilet in the hole as much as you can, find a bolt the size of the hole in the bushing. Place the bolt in the hole and hit the bolt hard, the bushing will pop out, it doesn't come all the way out just stuff more wet tp in and hit it again.

If you are running a stick and there was an automatic bolted on then you will need a pilot shaft bushing. 

I can't remember but there are other things to check, this getting old is hard on the memory. LOL

Oh, you can pull the plugs and see what is going on with the engine also, here is a link showing what the plugs look like by what is going on inside of the engine.
http://www.gas-mileage-enhancers.com/?p=505


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## Windows on Wash (Aug 30, 2011)

Great advice Jim.

I would go 4 bolt.


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## BigJim (Sep 2, 2008)

Just one more, if you really want to check the engine to see how much wear is on it, get a set of plastigage, they are not that high and you can see exactly how much slop or clearance is in your rod and main bearings. Check out this youtube video they show how it is done, I didn't watch it but if they don't tell exactly how to use the gage do a search it will tell you all you need to know.
https://www.youtube.com/watch?v=ulDX9Y4n0e0

To check the ring grove at the top of the cylinder feel to see if the lip is slight or large. Look in the cylinders and see how bad they are scratched, if the scratches are real deep, leave it alone. 

Sorry for straining your eyes writing so much.


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