Exhaust Gasket instl questions

[OldTee]

Could use a little practicle advice here. Ref SC 3.0.

I removed my exhaust system for some friendly R&R and found two exhausts leaking between the gasket and the head. The gaskets were installed with the metal reinforcment ring to the head which I think is correct. Is it? Next the exhaust gaskets have less than 2000 miles on them and look very good. Wisdom tells us not to reuse exhaust (or most other gaskets for that matter) gaskets. At $50 a pop I wonder if other alternatives are available?

The reason the leaks occured was, I think, because the PO did not properlly torque the nuts nor did he use any chemicals as a sealent. Any recommendations? As a precaution I am going to have the heat exchanger pipes plained.

Now another question. Would there be any benifit to putting two gaskets on each port? We used to do this on aircraft when exhaust leaks recourred but most aircraft had long manifolds that had some give in them. For the most part it worked, especially on Lycoming engines. If I were to do that, given gaskets have two sides, a smooth side and a side with a steet ring how would you put them together. Smooth to smooth, smooth to ring side, ring side to ring side? given that the ring goes toward the head (presuming first question is correct.)

[OldTee]

I can't believe that as many experts on this board that someone won't part with their opinion.

Q. Which way do exhaust gaskets go?

Q. Does anyone use a sealent? Which one?

Q. Has anyone doubled up gaskets? How?

[mtelliott]

Maybe there like me and just don't know. Because, I just tightened them down to what felt right. But, it's a darn good question. I would think that once you get them tightened and running, that the whole system would kind of oxidize together and provide a leak free seal. Guess I might be wrong on that.

[Jeff Alton]

I am about to do this on my 84. Try posting on the Technical Forum and see if you get a better response.

Jeff

[Jim Sims]

I was taught to put the metal covered side of the gasket towards the head. I have never stacked gaskets with the Porsche oem heater/header box or SSI systems as the length of the pipes gives enough compliance to allow the flanges to be pulled together. To salvage a bent or corroded carbon steel exhaust flange surface I have used a brass wire brush or medium coarseness rotary scotch brite pad to remove any loose corrosion products. Then I coat the bent or corroded flange surface with muffler/exhaust sealant (a sodium silicate compound), put the gasket on (non metal coated gasket side toward the sealant) and assemble and tighten the joint. Don't forget to put never seize on the studs. Cheers, Jim

[OldTee]

Thanks,

You said: "was taught to put the metal covered side of the gasket towards the head. I have never stacked gaskets with the Porsche oem heater/header box or SSI systems as the length of the pipes gives enough compliance to allow the flanges to be pulled together. "

You make sense. The PO did it the other way. I guess, in theory,
the exhaust stack will move and the steel ring provides a good seal. (If I read you correctly). One thing, there is a torque value for the flange nuts somewhere. It is important because if you pull it up too tight you will warp the flange causing a leak. Everybody just pulls them up to the torque value of "it feels good" and that can be a long term problem. I bet the racers don't do it that way!

[Jim Sims]

18 ft-lbs is the nominal value, but I use 15 ft-lbs (on the ones that I can fit a torque wrench up to) because I don't like breaking studs plus they have never seize on the threads which reduces the friction coefficient and makes the torque to tension conversion more efficient. The flanges on the last set of SSI's I installed were so thick there wasn't a prayer of bending them even with 18 ft-lbs. Cheers, Jim

[robs]

See also this answer from John Walker:
3.0SC Exhaust leaks

[chrisp]

I just recently used 3.2 gaskets. A ton cheaper. Don't know how they perform yet. Went in dry.

[Jim Sims]

I want to emphasize that the sodium silicate sealant is only used on severely corroded or warped flange surfaces; most of the time I just install the gaskets dry. Jim

[TerryH]

I haven't yet worked on the exhaust on my newly acquired Pcar, but in my previous "performace V-8" life, I've had to retorque headers/exhaust after a heat/cool/heat/cool cycle. Is that necessary on this application? I suppose a lot depends on the density of the gasket material.

[OldTee]

A little follow up to my questions above. Today I retrieved my heat exchangers after the machine shop plained the manifolds. What a difference. On the first pass it was evident that the flanges had warped and the manifold was not level. Cost $75 ea to do but just looking at the result I am sure my exhaust leaking problems are over.

[Thack]

Sometimes you can find copper gaskets. Copper is softer and conform to pitted or irregular surfaces better.

Mike