[lakeroadster]

Originally Posted by bentwings

I use SS bolts on the heads with lots of never-seize and standard gr 8 bolts ont he collectors ...again with never-seize. I don't like using the SS bolts but rust is more of a problem than strength.

Stainless has a higher thermal expansion rate than steel. Basically that means if you take two bars of equal length and heat them up, one stainless and one steel, the stainless bar will grow longer than a steel bar. Therefore every time the engine heats up, if you have steel headers and ss header bolts, the bolt load drops.

Steel bolts are a better choice for this reason.

[poncho62]

Yep...Those are all I have used for years....just keep them tight....

[vinniekq2]

I now have another source for the stahl pattern gaskets.That has been an issue for me where I live.

[bentwings]

Lakeroadster, I agree on the thermal properties.

Here are some values which seem to vary depending on whose book you look at.
steel is 7.3*10-6 In/in/deg F

Stainless is 9.6*10-6 In/in deg F

However the yielding length of the fastener is only about .375 in. (threads don't count). I don't have exact facts but I would doubt that the fastener would see greater than 300 deg F on the head assuming aluminum heads.

The difference in length is about .00082" stainless vs.
.00108" steel

or about .0003" rounding off. Pretty small amount considering that there is a compressable gasket. Also an alloy steel bolt has a greater yield value than a soft stainless bolt. So the SS bolt will act as sort of a spring if not over tightened. This is probably what the Belleville washer idea was to promote. Keep in mind that SS can have up to about 40% elongation vs about 20% for steel. Also there are other grades of SS which approach steel fasteners in yield specifications.

This is really getting into fine stuff and considering that the threads may not be clean, the bolt hole is not perfect, the flange is not dead flat on either side, and it is usually next to impossible to accurately torque a header bolt due to tight quarters.

I hate using SS fasteners on street cars however this is one area for which I give in ....but I use lots of Never-Seize and I am very careful about cleaning threads and other surfaces. Once burned, twice smart haha

[manicmechanic]

These are all great suggestions, but let's not forget the most important one of the thermal cycling. A cold engine and high revving either under load or not will tear up a set of gaskets quicker than anything else. Let your motor warm up before you get it hell. I also use the stock type manifold gaskets and I cut the flanges between ports more for a cleaner look but it seems to help with that stress as well.

[Stuntman Mike]

Anyone use Percy's? Supposed to be blow proof gaskets. I got a set awhile ago and never put them on. The ones that came with my headers are starting to leak though, so I guess its time.

[Stoppy]

I always have the best luck with the GM gaskets. CYA Joe

[Big Cliff]

i put on Thorley headers on my GMC Motorhome with copper gaskets that came with the headers and they said to toque them t 65 ft pounds and get it hot and let it get cold and retoque i only toque to 45 lbs i was afraid to put that much on a 3/8 bolt but they held without any leaks,

[maxdudy]

Originally Posted by chucksrt

I have a motor i built with doug thorley tri-y headers (vortec edelbrock e-tec aluminum heads) and the gaskets that the thorley's came with are already blown? Not even broken in yet. there is no noted torque spec. on the header paperwork. Does anybody have a gasket they can recommend? This build has been going on for far too long!! I would love to be done with it. It is in a 96 chevy express hi top conversion van.
thanks,
Chuck

Not knowing what happened and what you mean by blown ,I'll take a stab at it. If you added new gaskets at a new build, you have to tighten these maybe acoupel times. The headers expand with heat then contract cold. You normally start the engine, Run to temp then shut off. After engine cools, retighten the header bolts. do this severl times untill they stay tight. Some applications wiil never stay tight and need header bolt locks. Most exhaust gaskets are composit and work pretty well if gasket is not run untill blown out. This would indecate flange is warped or not flat with head serface.
Check out your issues. The gaskets you show in pics should work well, providing other issues are correct.

[pdmracing]

I drag race weekly & have great sucess with felpro 1406

& I reuse them on frequent tear downs & I even save the old ones and use on my street rides.

I use them with no coating. I use anti seise on header bolts. They go on nicely as you only need the end bolts to be put on and you hang the gasket on those two starter bolts, insuring correct alignment the first time.

If the headers or manifolds are uneven use a skim coat of this stuff

: Victor Mender and Exhaust System Sealer .

I use this on collector gaskets with zero blow outs. Also for repairs or holes in exhausts coat a screw or bolt with this and it will plug up to a 1/2 inch hole forever. I discovered this stuff over 20 years ago when my Ferrari headers air injector ports rotted out. I was broke so I used as a temporary fix, that was in 1987 & a 100k later still tight & leak free. I think its the same stuff that you use to seal wood stove pipes:-)

Hope it helps

[bygddy]

Originally Posted by pdmracing

I drag race weekly & have great sucess with felpro 1406

& I reuse them on frequent tear downs & I even save the old ones and use on my street rides.

I use them with no coating. I use anti seise on header bolts. They go on nicely as you only need the end bolts to be put on and you hang the gasket on those two starter bolts, insuring correct alignment the first time.

If the headers or manifolds are uneven use a skim coat of this stuff

: Victor Mender and Exhaust System Sealer .

I use this on collector gaskets with zero blow outs. Also for repairs or holes in exhausts coat a screw or bolt with this and it will plug up to a 1/2 inch hole forever. I discovered this stuff over 20 years ago when my Ferrari headers air injector ports rotted out. I was broke so I used as a temporary fix, that was in 1987 & a 100k later still tight & leak free. I think its the same stuff that you use to seal wood stove pipes:-)

Hope it helps

Ferrari+broke...?

[pdmracing]

Originally Posted by bygddy

Ferrari+broke...?

Oh yes broker than broke. I just got canned from my job & It was my daily driver, you should have seen the people at the unemployment office. Thats when I went self employed, 27 years ago. Still have the car too.

My mechanic turned out to be J Geils of the J Geils band. They ran a Vintage race shop out of MA. They knew I was a young vet, but they still charged me full price for service but showed me how to fix it with all the little tricks so I could do it myself. Being basicly hand built the italian repair manuals were useless. Most things were basic with some trap door somewhere, if you didnt know the tricks you would wreck something expensive. But I always left the engine to them. Remember this was before the web and Ferrari guys & clubs were mainly aholes and didnt do thier own work. In fact people would brag on how much they would pay for a service.

Sorry for the hijacking but the car has 157k on it now on original drivetrain and runs great, had a nice run coming home from caffine & octaine this sunday with a 55 Chev pickup with a 572 & a 871 Blower, imagine my surprise when he blew by me when we droped the hammer at 80+

[packratwrecker]

I've always used plain, old manifold gaskets. Slather the paper side with anti-seize & lock'em down.
15 years with the used headers on the 250, in the wrecker. Not 1 leak, except the collector gaskets, which I replaced with steel donuts.
5 years in my 94 GMC, with Edelbrock tubular manifolds(shorty headers). Only 1 leak on a back bolt that was hard to reach.

No special bolts, locks, gaskets, or nothing.

[1971BB427]

I'd leave the locks off your locking bolts for awhile. You'll need to check them often enough that it will be a pain to remove them each time, so save them for after the gaskets have seated. The bolts don't usually work loose until the gasket seats from heating, and then the resulting slack lets them begin to loosen.
I check/tighten mine after every short drive for at least the first half dozen times, and then they should stay tight and not leak so you can install your locks.

[vexzer]

The exhaust must be able to float with the engine vibration & movement. If the exhaust system is rigid that may transfer to the headers and header bolts. Use flexible couplings if you have to. For heat cycling, remember you must run the camotor for at least 90 seconds at WOT in top gear each time you get it up to temp -regular maintenance rules still apply.