Torque To Yield bolts on Intake Manifold

Mektek

Well-Known Member
Sorry if this is somewhat off topic, but the smartest heads in the house are here, so I could use some advice. I am replacing the intake manifold gasket on a GM 3.1 v6. I have all the needed parts, except new bolts. I'm reading in some places that it is recommended to replace the 8 bolts that hold down the manifold. Others make no mention of this.
They are not highly stressed like in a cylinder head, so I would like to reuse them. They might be TTY bolts, but I'm not sure. This is a big job that I don't want to do twice.
Suggestions?
 

Reprise

Lifetime VIP Supporter
I was about to write "reuse", and then I looked at your post more closely. This is the engine with the 2pc manifold and prone to coolant leaks with it, it appears.

From what I see, GM wants 18 ft-lb on those bolts (in three passes). If you have the same info, those wouldn't be a TTY bolt (at least, if it's made of 'regular' steel, etc.) No stretch would occur at that low a torque. (on edit: they're listed as a 3/8-16 bolt, and steel construction)

I'd reuse them, personally. But I've never touched a 3100. Let's see if anyone else agrees.

Looks like new ones come with blue locker, at least on the longer bolts. Make sure you reapply on the old ones.
 

Mooseman

Moderator
Moved to appropriate section.

I assume this is on a 60 deg.V6? I think @MRRSM has some experience with these engines.
 

MRRSM

Lifetime VIP Supporter
@Mektek ...Please Visit this site .... All of the answers are there in their FAQ and Engine Section. If the Member "ForcedFirebird" is still in residence... John can offer you the Best Help:

 
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Mektek

Well-Known Member
Thanks guys, it makes sense to me that at 18ft/lbs there is not enough force to make the bolt yield.
 

m.mcmillen

Gold Supporter
You might already do this but with anything I torque, I will torque the bolts in sequence until they stay at the specified torque. A lot of times when you torque something, gaskets get squished down and stuff settles so it might not be clamping as hard as it should.
 
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Mektek

Well-Known Member
Also, the torque is surprisingly low on the lower manifold bolts. I'm seeing 10ft/lbs in one write up. 18 is for the upper part. At such a low torque no bolt will stretch.
I'm using the Victor Reinz gasket which has steel spacers to prevent you from overtightening and crushing the gasket. So if I do 15ft/lbs it should still be OK.
 
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Mektek

Well-Known Member
done! :2thumbsup:
Hell of a job but it went as well as could be expected and I ended up with no leftover fasteners. So I give another vote for reuse the bolts and don't waste money on new ones unless you see damage on the old ones.
I hope I never do this job again :satan:
 

TollKeeper

Well-Known Member
@Mektek - Just seeing this thread, my apologies. There are 2 different engines mentioned in this thread. For the 3.1, I would just reuse the bolts, and not even bat an eye. for the 3100, you have to carefully inspect each bolt, bolt housing, and use best judgement, and if you question anything, to replace it. Even thou the 3.1 and the 3100 share the same displacement, and are essentially the same block, they are completely different animals.
 

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