Constantly Having to Re-Torque Exhaust Bolts

[Solarguy]

I installed Remflex Exhaust manifold gaskets using new bolt kit on my 70 340.  I am using 10 conical washers on the bolts/studs and the 2 barrel nuts on passenger side.  Remflex as well as the service manual recommend 20 ft lbs torque.  Remflex Claims that re torqueing is not needed yet EVERY Time I take car out a slight leak can be heard after 1/2 hour of cruising.  A trip back home and a hot re-torque quiets everything down so I know that is the source of my noise. 

I used anti-seize on all the bolts/studs and DA'ed and straight edged manifold gasket surfaces and everything looked ok.  Heads are stock and also straight edged.  The Remflex gaskets are 100% graphite and much thicker than regular gaskets.  The bolts are NOT backing out as I have marked  them and when re torquing them, they tighten more.  I'm guessing that they just need to be bedded fully despite remflexes claims of never needing re torquing. 

I know the factory didn't use gaskets there and there is differing opinions whether conical washers are to be used at all 10 of the 12 bolt/stud locations.  I was replacing a set of felpros that were on there for 20 years.  That set used 10 conical washers and never leaked until recently which led me to these remflexes. 

These are the gaskets, much cheaper on Amazon

http://catalog.remflex.com/MOPAR_Header_Exhaust_Manifold_Gasket_p/6027.htm


Any remflex users here or any ideas?

Thanks

[7212Mopar]

I am using Stage 8 locking fasteners in SS for my headers mounting to aluminum heads. They stay in place and no leaks. However they do not look stock but neither are my headers. I think Summit has their own lines of locking fasteners that is cheaper. SS cost more but they do not rust. Important with stock heads where the studs go into the water jacket.

[Bullitt-]

I know nothing of the specifics of what your dealing with but you say that you re-torque "hot"....
That runs counter to what I have learned as the materials have expanded when hot and wait till things are cool to re-torque. 

[MoparLeo]

Always tighten them after they cool off and contract.  I see that the theory would be that if you tighten them hot, that they would get tighter after the bolts, nuts cool off, but it is not the fastener getting loose but the gasket compressing. Now if you had no gasket the only thing that could be happening is that the bolts/studs are stretching.

[Solarguy]

Thanks for the responses.  I agree with the idea of only torquing when cold and was reluctant to tighten hot and did it just to verify that that was the source of the noise, it was.

I think, contrary to the companies claim, these type of gaskets are gradually compressing with heat cycles and need to to take a "set"  which requires re torquing, which I will do now only when cold.   

Regarding the conical washers, I don't know if they are helping or hurting.  The service manual says to use only on the 4 studs yet the parts manual and the kits come with enough to use on the other 6 bolts.  I have seen people do it both ways.???? 

[dodj]

I use remflex with headers and do not have the same issue. They have been excellent. Wonder what the difference is.

[Brads70]

My first thought was... are you certain you don't have a cracked manifold?   

[Solarguy]

My first thought was... are you certain you don't have a cracked manifold?   

I cleaned them good and looked real closely but that is possible.  I only hear a noise after cruising for about 1/2 hour when engine is fully up to temp.  yesterday, when I tighten them up hot and went for another ride, the noise was gone.  I just got back from a run now and same thing, fine at first 1/2 hour then rattle type exhaust noise from same area.  Also noted that leak is only under load, if I shift into neutral, (automatic) noise goes away???  I'm going to wait until engine cools and check torque.   

[Solarguy]

I use remflex with headers and do not have the same issue. They have been excellent. Wonder what the difference is.

I don't know, They look like quality gaskets.  I've been using them for years on the head pipe to manifold with no issues.  I just changes the manifold to head ones last month and have been battling with small leak ever since. 

[Solarguy]

I am using Stage 8 locking fasteners in SS for my headers mounting to aluminum heads. They stay in place and no leaks. However they do not look stock but neither are my headers. I think Summit has their own lines of locking fasteners that is cheaper. SS cost more but they do not rust. Important with stock heads where the studs go into the water jacket.

I'd rather stick with stock type fasteners with the manifolds.  I've been marking the bolts/nuts I can see and they are not backing out so either the gaskets are compressing, the bolts are stretching, or the conical washers are not returning to same height/tension.  Torque is only 20 ft lbs so I doubt there is much torque stretching going on with the bolts/washers.  Heat stretching maybe

[Solarguy]

So, I went for ride this morning, nice and quiet for first 1/2 hour then same rattle/popping noise starts happening.  Happens only in gear d 1 2 and r.  If I'm cruising and slip into neutral, noise stops. 

Is it possible to  only have an exhaust leak under load? I would think yes. 

[Burdar]

Check the rest of the exhaust connections for signs of leaking.  Check your motor mounts too.  Any excessive movement will put strain on the exhaust components and could cause a leak.

I didn't use any gaskets on my 318.  I just put a light smear of copper silicone on the sealing surface and let it dry.  Any extra that squeezed out was pealed off.  If all else fails, just remove the gaskets and try it without.

[Solarguy]

Check the rest of the exhaust connections for signs of leaking.  Check your motor mounts too.  Any excessive movement will put strain on the exhaust components and could cause a leak.

I didn't use any gaskets on my 318.  I just put a light smear of copper silicone on the sealing surface and let it dry.  Any extra that squeezed out was pealed off.  If all else fails, just remove the gaskets and try it without.

Copper silicone is going to be Plan C.  Plan B is going to be to lose the conical washers on the center dumps, then the inner 1 and 7 washers if that fails, then silicone without gasket. 

I checked the whole exhaust + motor mounts when the car was on stands last month, looked good. 

[MoparLeo]

Remove the manifold and check exactly where the leak is on the gasket. It will show as a carbon leak. That will narrow your search as to exact fastener/manifold location of the leak. Could be many things but you have to see it not necessarily hear it to narrow it down. Cracked gasket/cracked manifold/or... Try a quality header gasket. I chased a leak for years and finally use 2 Mr Gasket non reinforced "asbestos" type gaskets doubled up and leak ended for over 20 years until motor replaced.

[Solarguy]

UPDATE:

So I just got back from an hour long cruise in 90 degree weather including a 10 minute idle at the 17st Causeway drawbridge  and am happy to say, NO LEAKS.

Yesterday, I removed the 4 conical washers from the center dumps 3/5 and 2/4 and re-tourqued everything.  I left the conical washers on the 2 long bolts on drivers side 1/7 inside as well as the 4 outside studs left/right. 

Only AFTER I was having problems did I read the service manual and parts book, after all, it's only new gaskets and bolts right.  The service manual says to NOT use them on the center dumps and the parts book calls out 4 for the outside studs and 2 "as required" for the drivers long bolts.  I used the bolt kit from Roseville,(AMK) which came with 10 conical washers which I used them all. 

I'm happy the leak has stopped yet confused why the kit would come with 10 washers, its for 68-70 340 hi po exhaust manifolds.  Also why the parts book would describe the ones for drivers side 2 long bolt washers as being "as required", so how did they come from the factory?

I've been around mopars long enough to know there is always a quirky exception to the rule on just about everything.  I'll chalk this up to that if no one has a reason. 

I wanted to post the conclusion of this saga so anyone else using the bolt kit can review.

Here is a service manual and parts book references