Big Block Exhaust gasket VS No Gasket

[68rt]

Anybody have any imput on whether or not to use a gasket with stock exhaust manifold (manifold to head area)? I know they did not come with a gasket from the factory? I know you need them with headers. Thanks

 

[BeastlyBirdie]

any cold air hitting the valves would be bad. If you think your machinist can get the exhaust manifolds and exhaust side of the head mated, go for it. I know where I was a machinist, we always told people to run a gasket. And we were very good.

 

[Cranky]

any cold air hitting the valves would be bad. If you think your machinist can get the exhaust manifolds and exhaust side of the head mated, go for it. I know where I was a machinist, we always told people to run a gasket. And we were very good.

You would need to have a pretty large gap for cold air to do any damage. Hot head along with a hot manifold....how much cold air is going to get to the valves? Even a header tube is going to cold off much faster than a stock manifold will and how many people have had problems with open headers cooling the valves too fast when the engine is shut off.

Anybody have any imput on whether or not to use a gasket with stock exhaust manifold (manifold to head area)? I know they did not come with a gasket from the factory? I know you need them with headers. Thanks

If your manifolds are flat and have no gouges in the sealing faces, I don't see why not but most headers don't have a flat face and need gaskets.

 

[67 coronet]

gaskets are just insurance vs leaks.if they dont leak,run em without.most of the original manifolds have warped and pitted enough to leak without gaskets.

 

[BeastlyBirdie]

Actually cranky, by cold I mean less than exhaust temp. That will cool one spot, thereby warping valve surface. That's why you run at least header stacks, not just open ports. Its not anything to do with shutting the engine off, its to do with while the engine is running that valve is having one spot cooled by external air. Its not able to rotate except on exhaust stroke. Will it be immediate damage, no. Will it shorten the life of the valve, you bet.
As for the original poster, as you mill the exhaust side of the head, you also mill the manifold, and since the head had been surfaced, everything is sitting in a position than 40 years ago. Will it effect the seating, probably not, but why run the risk.

 

[Meep-Meep]

I have done both. Gaskets and no gaskets (use high temp silicone in place of a gasket). When I put tri Y's on my SB 68 Mustang I didn't use any gaskets even at the collector, but everything was flat. I ran like that for 7-8 years and sold the car and who know how long it stayed together after. Plus I always use new split lock washers at the header bolts. I did the same orange silicone trick with my hemi charger's exhaust manifolds and no issues. My 340 GTS Dart doesn't have gaskets either. The trick to reusing manifolds is you only have one shot from new so when you reinstall you must surface the manifold. Sanderson headers advertize "no gaskets" and when I put a set of block huggers on my 71 F250 I did exactly what they said and it works.