Exhaust Gaskets or Not?

[rehoward]

I have bought brand new cast iron OEM type exhaust manifolds for my 1993 K1500 with the 305 V8. They came with exhaust gaskets but the old OEM ones had no gaskets.
I know some people recommend not using the gaskets because maintaining bolt torque is difficult even without using gaskets, and having the extra compression of the
gasket just compounds the loose bolt problem. My inclination is to use no gaskets, hi-temp anti-seize on the bolt threads, and proper bolt torque of course. This is a
totally stock truck/engine used for occasional towing.

Any opinions on this topic? Thanks

Randy

 

[Sean Buick 76]

I use Remflex gaskets on everything, manifolds or headers. They are graphite and have a bounce back effect that keeps your bolts from loosening up over time.

 

[fancyTBI]

I never install exhaust manifold gaskets. Torque them down and check them intermittently after getting some miles on it.

People do seem to have good luck with other styles.

 

[Schurkey]

Reduce bolt torque when using anti-seize. The amount varies with the kind of anti-seize used. 10--20 percent torque reduction is common.

Following the service manual is recommended in terms of using/not using gaskets. OTOH, I really like installing iron exhaust manifolds with no gasket--keeps the manifold cooler by allowing heat transfer back to the cylinder head/water jacket.

Suggestion: Put a straightedge across those exhaust manifolds. It's REALLY common for them to be horribly warped right out-of-the-box. I think the Chinese machine them while they're still warm from the casting process, they haven't settled-down yet. They're straight when they come off the milling machine, but then the casting cools/settles, and they're not flat any more. Whether the high-speed machining gets them smooth enough is another story.

I've replaced the exhaust manifold on my Trailblazer a couple of times; and I bought reproduction "Corvette" manifolds for a 454. I've gotten so that I have my machinist put them in his parts-cleaning oven while he's baking other work. They get heat-cycled a few times. Then I have him plane them flat and smooth before I'll install them.

And beware casting flaws in the aftermarket exhaust manifolds. The Chinese ones are bad...the Viet Namese manifolds are worse, according to my machinist.

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[rehoward]

Good stuff friends. I think I will check flange surface straightness on the new manifolds and if flat just bolt them on sans gaskets.
Good advise on reduced torque for lubricated threads. Can't really see why Chevy put those silly bolt retainer lock devices on
OEM factory applications unless they were there to keep the loose bolts from completely dropping out. At any rate, gasket or no gasket,
I will re-torque the bolts several times after running until everything settles in and all compression and/or bolt stretching is stabilized.
Seems like there should be a better way. I am interested in the Remflex gaskets. I had not heard of those.

Randy

 

[udidwht]

As for anti seize...

Buy a bottle of Mom's Milk of Magnesia' then leave the lid off until the carrier liquid evaporates. Cut the container open and use a dab of it to coat threads liberally. Better than copper paste.

 

[Sean Buick 76]

Honestly just use the Remflex gaskets, torque them to 23 foot pounds and forget about the situation they won’t leak even with severely warped manifolds or headers or heads. The bolts will never need to be retightened EVER.

 

[someotherguy]

Honestly just use the Remflex gaskets, torque them to 23 foot pounds and forget about the situation they won’t leak even with severely warped manifolds or headers or heads. The bolts will never need to be retightened EVER.

I've heard many times that OEM didn't use gaskets, but that made sense because they were assembling brand new parts with freshly machined surfaces that are presumably better (maybe that's not always true) and things just fit better.

I've never taken exhaust manifolds off any engine though and not found gaskets behind it already. Whenever I've gone back in to replace, I've always used the Fel-Pro perforated steel type which I believed to be an OEM design, yet if they allegedly came with no gaskets, not sure where I got the idea these were OEM - maybe I got that idea because this was "the" type of gasket always available, going back many, many years.

This type of exhaust manifold gasket has never given me trouble, even when used on cheap headers back in the day. (country miles better than that paper garbage they included with them.)

YMMV

Sean - those Remflex do look/sound nice, though. I could see using them in a situation where other gaskets might not solve the issue.

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Richard

 

[Schurkey]

I looked-up exhaust manifold replacement in both the '88 C/K and the '97 C/K service manuals.

The '88 manual does not reference exhaust gaskets in the text.

The '97 manual shows gaskets in an illustration. There is no similar illustration in the '88 manual. The '97 manual does not reference exhaust gaskets in the "exhaust manifold replacement" instructions on page 6A-165. However, the exhaust manifold replacement (Right side/Left side, individually) instructions on page 6A-194--195, the gaskets are specifically mentioned.

Point is, even the '97 manual is inconsistent in whether a gasket is required. Depends on which set of instructions you're looking at; and whether you consider the illustration definitive or generic.

The '88 manual shows "tab washers" (French locks) but the '97 does not. The torque specs for the exhaust manifold bolts are different between '88 (26 ft/lbs for center two bolts, 20 for the end bolts) and '97 (15 ft/lbs first pass on all bolts, 22 ft/lbs final pass on all bolts.)




I would be very tempted to use NO exhaust manifold gaskets provided the head and manifold measure flat with a straight-edge, and I'd use the '88 torque specs.

 

[Firewood truck]

I used some Mahle laminated steel gaskets when I had the manifolds off of the L31 before stuffing it back into the truck. Back in the day, Ferd used to use grease between the manifold and head, once it got hot it would solidify and seal up the manifold. It was a miserable mess to deal with when you had to R&R an exhaust manifold.