After trying 2 different gaskets and sealer with one, I still couldn't eliminate the spitting sound and stumble at idle I got with an exhaust leak between the head and intake/exhaust manifold. Decided to try one more time and use a Remflex gasket this time. I did notice that the gasket surfaces on the head were pitted badly in spots. Can anyone advise me on whether I should use any kind of sealer on this gasket? 53 Chevy truck with 216 George

In 60+ years of doing professional mechanic work, I've never been able to find a sealer that will stand up to exhaust gas temperature. Now, in about 3-2-1 seconds, somebody who has read three copies of Hot Rod Magazine and found at least five internet references will tell you I don't know what I'm talking about. It's up to you to choose who to believe. The only cure for pitted gasket surfaces is a milling machine and a fly cutter.
Jerry

I agree with Jerry, but if you were to get a gasket to take up the pitting it would be the remflex, however no guarantees.

Weren't exhaust manifold gaskets back in the old days made out of asbestos? (OMG, did I actually say that word? )
They probably had enough resiliency to seal without any sealant, which like Jerry says, can't stand the heat. Even JB weld won't work above about 250F.

J-B Weld can withstand a constant temperature of 500 °F (260 °C), [en.wikipedia.org] and the maximum temperature threshold is approximately 600 °F (316 °C) for 10 minutes.[9]

OK, but still not high enough for exhaust temps.

From J-B Weld's Site [jbweld.com]

Will J-B Weld work on an automotive exhaust?

Because of the extreme temperatures of exhaust systems, we do not recommend J-B Weld for use on exhaust manifolds and catalytic converters. Nor do we recommend the product for repairs within the combustion chamber. However, in areas where the continuous temperature is less than 450º F, we do recommend our HighHeat epoxy putty stick.

I've seen exhaust port temperatures in the neighborhood of 2000 degrees F. on dyno runs of race engines at full throttle. The headers were translucent enough we could flames dancing arouind inside the pipes!
Jerry

The is the Engine Shop not the HiPo Shop.

Would normal Stovebolt engines have those 2000 degrees temperatures?

Probably would on heavy load. My Diesel runs around 300F at idle, and will hit 1200F. The pyrometer is at the outlet of the exhaust manifold. Gas engines typically run hotter than diesels. We had a Model A exhaust manifold cherry red once when the timing was too retarded.

Watch the exhaust manifolds on a 454 Chevy engine in a motorhome on a long uphill pull. They get red hot, and those are cast iron, not thinwall steel tubing. That's well over 1000 degrees, probably closer to 1500. I've made several test runs with different motorhomes with the engine cover off, trying to diagnose detonation noises that were causing cracked spark plug insulators and burned valves. A stovebolt engine will probably do something similar pulling a hill at close to maximum gross weight. A Cowboy Cadillac that never does anything more stressful than hauling an iced-down Yeti cooler full of beer to a tailgate party, not so much!
Jerry

Does anyone have data/measurement on standard-equipment 216/235/261 engines?

Just use the rim flex. It will do the job you want it to.

Hmmmm .... seems that was established in the first few posts?

Thanks, Dragsix

Geo55,
Did you pinpoint the actual leak? It's not where the large square part of intake meet exhaust?. My 235 did a tiny tick when I first built it. I re-tightened the 9/16 bolts and the tiny "tick" went away..

My 37 Buick with a 263 straight eight is even more of a manifold headache than a straight six. Since we make LONG trips I probably had more trouble than others that didn't have the manifold hot for sixteen hours at a time. I welded, brazed, or stainless tigged several during the last 40 years and finally found a virgin replacement which gave me the incentive to try something different. After surfacing with the intake and exhaust bolted together I threw away the alignment rings and used studs to help align during installation. Finally I discarded the exhaust gaskets and used high heat (red) silicone. With this configuration I've had no leaks for the last fifteen years. One possible explanation is that it lets the manifold "creep" around between hot and cold cycles. I really don't care as long as it keeps the big sucker off the welding table.

[img]https://i.postimg.cc/VrNRhvNX/Pont-heater-Buick-sealant-003.jpg[/img] [postimg.cc]

Mine makes a spitting sound intermittently at idle accompanied by a stumble. I tried tightening the bolts a little tighter and it didn't help. I spent the $42.00 and ordered the remflex gasket. The motor runs too good otherwise to warrent pulling the head for machine work. I'm thinking the thicker gasket with the extra graphite cushion might mask any imperfections on the machined surfaces.

Keep us posted Please.
Todd

The rim flex actually is about three times as thick as the stock gasket when you first install it, but it is soft and squeezes and compresses down. It’s a great gasket to use and solves any number of intake and exhaust flange sealing issues.

Glad I ordered one. Sounds like it will solve the problem. Hope someone who has used a remflex will advise me as to use any sealer on it or install it dry.

It’s all I have used the last number of years. Probably 10 different motors. No sealer is required or needed.

we used the remflex on generator exhaust in Alaska, we tried every thing under the sun, but this is the only thing that worked, and worked well.

With regards to cast iron exhaust manifolds, an engine development engineer once told me that one of three things is always going to happen:

1) The manifold is going to move (expand and contract).

2) The manifold is going to break.

3) The manifold is going to break something else.

I think that your solution is definitely compatible with #1.

GMC 270s are known to crack manifolds from time to time. When I rebuilt mine, I made sure that both the contact surfaces of the retainers and washers, along with their corresponding surfaces on the manifold were smooth. Not sure how much this will help - but hey.... it couldn't hurt.

Best Regards...