# Exhaust manifold seal restoration



## Windows on Wash (Aug 30, 2011)

Start soaking them now...everyday. 

Acetone and Transmission fluid mix.


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## huesmann (Aug 18, 2011)

Could be coarse thread (1.5mm) where your tap is fine thread (1.25mm). Or vice versa.

If you already have the bolts, take them to HD and use their bolt identification tool to confirm dia and pitch.


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## papereater (Sep 16, 2016)

I will go to HD, but from what I hear pitch is measured by counting the threads over a distance, then divide distance in mm by thread count, example, 23mm length divided by 16 threads = 1.44. That is neither 1.25 nor 1.5, (scratching scalp, confused)........Oh well.


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## ukrkoz (Dec 31, 2010)

*10mm *1.50 1.25


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## papereater (Sep 16, 2016)

ukrkoz said:


> *10mm *1.50 1.25


But UK, why do I get 1.44? Something is not right. Either my metal metric ruler, or something else.


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## SeniorSitizen (Sep 10, 2012)

3/8" - 16 was common for those studs unless you know for certain they are metric. 

Thread pitch = the distance from one thread to the corresponding point of the next thread.


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## papereater (Sep 16, 2016)

SeniorSitizen said:


> 3/8" - 16 was common for those studs unless you know for certain they are metric.
> 
> Thread pitch = the distance from one thread to the corresponding point of the next thread.


Wow- surprise! Yup, I suspected maybe they are not metric. We dont know for sure yet, but tomorrow I am planning to stop by HD and try what Huesman said. No other way to know. unless, I call felpro tech service tomorrow- yeah- good idea, they gotta know. 

Thanks. I will advise asap.


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## SeniorSitizen (Sep 10, 2012)

Do you have a set of feeler gauges? Those in conjunction with a adjustable end wrench ( Crescent ) can be a fairly accurate caliper.


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## Oso954 (Jun 23, 2012)

> but from what I hear pitch is measured by counting the threads over a distance, then divide distance in mm by thread count, example, 23mm length divided by 16 threads = 1.44.


You either heard wrong or are remembering it wrong. Thread pitch (metric) is a simple measurement from the peak of one thread to the adjacent thread peak. If you are looking at a 10mm bolt, the fine thread (1.25mm) vs coarse (1.5mm) you need to be precise enough to pick up the 0.25mm difference.

US threads are typically threads per inch (tpi). 

This will explain it better.
https://www.boltdepot.com/fastener-information/measuring/tpiandpitch.aspx

If you hit the links on that page, you can see the typical tpi or pitch for Some metric and US bolt sizes.


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## papereater (Sep 16, 2016)

Oso954 said:


> You either heard wrong or are remembering it wrong. Thread pitch (metric) is a simple measurement from the peak of one thread to the adjacent thread peak. If you are looking at a 10mm bolt, the fine thread (1.25mm) vs coarse (1.5mm) you need to be precise enough to pick up the 0.25mm difference.
> 
> US threads are typically threads per inch (tpi).
> 
> ...


Thanks Oso. I just figured I would minimize my error if I counted over a longer span as I dont have such a high precision tool. Anyway, looks like Im on the right track. Looking more and more that is is not a metric like Senior said.


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## sestivers (Aug 10, 2007)

I wouldn't have guessed a Pontiac to use metric fasteners. Was it rebranded by a Japanese mfr? Are the other engine fasteners metric?


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## ChuckF. (Aug 25, 2013)

Quite possibly not metric; on older design engines that have been around for decades they don't change fasteners to metric for no good reason. My Dodge truck has some of each. 

If you don't have a thread gauge, try putting in known bolts from your stock.


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## huesmann (Aug 18, 2011)

Oso954 said:


> You either heard wrong or are remembering it wrong. Thread pitch (metric) is a simple measurement from the peak of one thread to the adjacent thread peak. If you are looking at a 10mm bolt, the fine thread (1.25mm) vs coarse (1.5mm) you need to be precise enough to pick up the 0.25mm difference.


But it sounds like that's exactly what the OP is doing—measuring X distance over Y number of threads, and dividing X by Y, which gives thread pitch in mm (assuming measured in mm!). If you can only measure one thread then the 0.25mm precision matters, but measuring over many threads will give you a decent result even if your measurement tool is only 1mm accurate.


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## Bigplanz (Apr 10, 2009)

Thread pitch gauge. They have them for SAE and Metric. Easiest thing to do is take it to HD or Lowes and find out what the nut threads on to.

https://www.lowes.com/pd/IRWIN-Stan...6Zck2Q4BBZZl8SMtuvYry_1Ir8jI4LVhoC4G4QAvD_BwE


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## SeniorSitizen (Sep 10, 2012)

Unless I'm mis-reading the OP, his Pontiac exhaust manifold has studs. Although fine threads are superior on many applications I've never seen fine threads on manifold studs, possibly on the nut end but not on the manifold end.


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## SeniorSitizen (Sep 10, 2012)

QUOTE:
I have the bolt/seal/spring set.
********************************************************
Please tell us exactly what *bolts* are in this set. If you can't post a picture just describe those bolts.


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## Oso954 (Jun 23, 2012)

> But it sounds like that's exactly what the OP is doing—measuring X distance over Y number of threads ......


Look at the link I provided. TPI is measured from valley to valley over one inch.

Thread pitch is measured from peak to peak. It you are going to measure it over a distance, you need to be starting and ending the measurements in the right place. 

Starting and ending in the valleys would throw the total length off.


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## papereater (Sep 16, 2016)

sestivers said:


> I wouldn't have guessed a Pontiac to use metric fasteners. Was it rebranded by a Japanese mfr? Are the other engine fasteners metric?


Sorry for late reply, Ses. 99% of the car's bolts are metric, like all other cars(?). 

I have nnot yet had a chance to try to size it at HD. New Year Hype ans all going on.........


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## papereater (Sep 16, 2016)

SeniorSitizen said:


> Unless I'm mis-reading the OP, his Pontiac exhaust manifold has studs. Although fine threads are superior on many applications I've never seen fine threads on manifold studs, possibly on the nut end but not on the manifold end.
> 
> 
> 
> https://youtu.be/cTRUXRv2HFs


Great video, Senior! I looked all over and coundnt find anything having to do with exhaust manifold bolts. Good to know. But man, what a chore- I might have to remove the whole thing and put a torch on it. All I have is propane.


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## papereater (Sep 16, 2016)

SeniorSitizen said:


> QUOTE:
> I have the bolt/seal/spring set.
> ********************************************************
> Please tell us exactly what *bolts* are in this set. If you can't post a picture just describe those bolts.


Here:

https://www.rockauto.com/en/moreinfo.php?pk=123487&cc=1260784&jsn=2184


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## papereater (Sep 16, 2016)

Cant wait for all this festivities to end, so I can have fun with my old car.......


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## huesmann (Aug 18, 2011)

Yup, studs, not bolts. Still, you should be able to take them to HD and determine their actual thread.

My guess is that they are actually 5/16-24. :biggrin2:


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## SeniorSitizen (Sep 10, 2012)

papereater said:


> Great video, Senior!


Maybe someday the fellow in the vid will discover how much better a small pipe wrench like a Rigid 6" works for jobs like that. :smile:He mentions not depending on vise grips but the channel locks are nearly as bad.


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## papereater (Sep 16, 2016)

huesmann said:


> Yup, studs, not bolts. Still, you should be able to take them to HD and determine their actual thread.
> 
> My guess is that they are actually 5/16-24. :biggrin2:


Wow- hueasman, how did you know that!!?? That is exactly what they are. And yes, technically they are studs, not bolts. 

So, turns out I finally got the studs out without much force, and they were not fused. After 32 years, who would have figured. Anyway, I screwed in the 2 studs, and the studs come with a bottoming out flange, so you just bottom out, and then you should be OK. UNLESS I DID THIS BACKWARDS! 

The tech guy at felpro said the flange end goes on the bottom end, but that didnt make sense to me as when configured this way the new stud assembly does not mirror the original set up. Now, after installed I started tthe car up 
and dang, I srtill am getting fumes sneaking out the gasket/seal. I checked with soap bubbles, so then Im thinking did I install backwards with the limiting flange preventing me from squashing down the seal even more providing a tighter seal? 

I hate to smear high temp silicone red goo into that seal. What would you do? Turn the studs upside down from how they are now installed and try it out?


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## huesmann (Aug 18, 2011)

Not sure exactly where on the car this joint is, but in general the flanged end of the stud is on the upstream end of the joint, i.e. you slip the mating flange for the next downstream piece of exhaust onto the studs and nut the flange on the studs.


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## papereater (Sep 16, 2016)

huesmann said:


> Not sure exactly where on the car this joint is, but in general the flanged end of the stud is on the upstream end of the joint, i.e. you slip the mating flange for the next downstream piece of exhaust onto the studs and nut the flange on the studs.


Ok, that would mean I installed it reverse. I can reverse it. Strange how factory does not have this flange, the narrower base of the spring just sits on the nut end/base. 

Again, if still useful, heres the picture of the new replacement studs:

https://www.rockauto.com/en/moreinfo.php?pk=123487&cc=1260784&jsn=2184

Note that the springs are not supposed to be installed in the direction shown on the picture, but upside down such that the narrow end goes on top, touching that nut.


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