Technical Sbc exhaust manifold question/help

Hey guys I have what I believe is a sbc 305 and just bought a set of tru-ram natural finish cast iron exhaust manifolds from speedway. My question is would you guys just use high temp exhaust silicone as a gasket or would you use a Normal gasket to install? The application is in a 32 pickup. Also would you guys have the manifolds coated or just leave them in their natural finish?

 

Natural finish for me.. and back in the day the factory didnt use gaskets.. But I use the FELPRO ones myself.

 

Also using that red temp silicone on a exhaust manifod, When it squishes out looks down right NASTY !

 

Would you use a light silicone bead to just hold the gasket to the manifold to help keep them in place for install?

 

Don’t need to hold in place the exhaust manifold gaskets for the iron manifolds will catch on the mounting bolts.

 

No gasket on a small block.

 

nope.... no silly stuff



Kinda self explanation...

 

I have heard that the factory never used gaskets, but the heads and manifolds had better be damn straight to not leak. My luck is never that good. I use the FelPro gaskets mentioned above.


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Awesome thanks for all the help guys, and sorry for the noob questions! Those definitely are different then the ones provided with the manifolds, I’ll have to get some of those. Just to be safe would you have the manifolds machined and made sure they’re flat or run as is right out of box?

 

The ONLY Sto0pid question is the same one asked twice !

 

Put a straight edge across them

 

The Eastwood Company has a real good manifold coating you can spray or brush on. Comes in cast color or silver I believe . And yes, use gaskets.

 

Just bolt them on, and run it. No sealer, no gaskets. But use lock tabs on the bolts at the outer bolt locations, like Chevy did.



and a thick, small OD flat washer between the lock tab and the manifold, and under the two center bolts also.

I would probably spray the manifolds with black high temp paint, and watch it bake off over time.

 

I painted stockers on my 57 Fuely with the Eastwood cast color and put on BBQ--they lasted great for years.

 

Lock-tite on the bolts if you don't have the tab locks. With gaskets they will loosen, probably.

 

Paint or coat them now before they rust.
I used some VHT on mine. Followed the baking instructions. So far so good.
I have used the orange silicone, doesn’t need much, with no issues.
I am using the 3 piece (each side) gaskets on my rams horn manifolds. No issues.
I have also not used anything without issues (on Fords)
It’s all up to you.
Glad I could clear it all up

 

When they were new they were straight on both surfaces and didn’t leak.

 

I used gaskets on mine, they came with the Dart aluminum head set. I sprung for good stainless bolts and washers from Ace Hardware, $36 IIRC.

I had the manifolds glass beaded, chopped off anything I didn't like and smoothed them over. The driver side was from a '65 or '68 Chevy, passenger side from Dorman, fits a Chevy truck with a 45-degree dump. Painted with POR15 manifold paint and baked in the over per what the can said. The finish is durable coming up on 5 years.

 

Buy gaskets. They are cheap and work well.

Do Not go for "header" gaskets but the stock ones with the tin on the outside and the gasket material on the inside.

 

I think Chevy never used gaskets on them, to improve heat transfer from the manifolds, so they wouldn't get too hot.

But the aftermarket engine gasket sets include gaskets for them. They are not needed.

 

Chevrolet doesn't have a part # for a cast iron manifold gasket. Not gonna convince them Jim.

 

If you have gaskets that are the metallic style shown above, but don't have the same open bottom holes; just use a pair of tin snips to open the holes up. Then you can bolt up the manifolds loosely, and drop the gaskets in place, and tighten them down.
I'd never run a SBC without exhaust gaskets, whether the factory did or didn't. Never lucky enough to not have them leak.

 

I agree with Jim as long as the head surface and the manifold surface are straight and flat and both are cast iron.
As Jim says the direct contact aids in keeping manifold temp down by way of increased heat transfer, and the solid contact allows you to put some actual stretch tension on the bolts, which aids in keeping them tight.

 

New manifolds won't be warped, so install them without gaskets. IF they do leak, then install some gaskets that come in gasket kits, that most guys don't use on their manifolds, so a shop may just give you some. I am Butch/56sedandelivery.

Just went to the Speedway site, the manifolds come with the gaskets, so use them!

 

I'm another one that uses Fel-Pro exhaust manifold gaskets.... Including with headers with or without the 1 piece header flanges...

 

I have the same manifolds. I had them hitemp coated (Before they had Been installed)in a cast iron color. Sort of gives them a stock appearing look.

 

A old timer once told me years ago , never remove a warm or hot manifold from a engine because it will warp when it cools , for what's that's worth ??????

 

Butch you are correct new manifolds are not warped but only if they are new GM. These are Speedway made in China hence the gaskets.

Pat