Technical flathead exhaust manifold installation

I am using stock cast iron exhaust manifolds on my flathead build, should I use gaskets under the manifold or not? Theory has it that the gaskets insulate the manifold and cause warping. The manifolds have been machined and mate to the block smoothly.

 

I always use them - can see no real reason not too. My guess is that you'll have exhaust leaks without them. You can always try it without gaskets and see if you have any leaks? Always use a lot of anti-seize on the bolts (and all down the sides of them) - to prevent rust. Also, if you didn't notice, on each side, two of the bolts are 7/16, the other four are 3/8. I've seen a lot of guys wonder why they 'stripped the threads' out of the 7/16 ones - due to having 3/8 bolts in them.

 

Never heard of that theory.... I am no expert but experience tells me you should install the gaskets.

 

Never heard of that theory, but if the manifolds are machined flat they should work without gaskets just fine like many SBC's.

 

Henry thought they were a good idea, but what did he know?

 

Who told you this theory? Was this person hearing voices?

 

Depends on the quality of the machine work. Shouldn't need a gasket if both sides are flat. You will find out when you crank it up . Then you can take it all apart and put gaskets in it.

 

Machining both parts flat will leak. Now if both are machined flat then lapped together they will seal. If they are perfectly lapped together and you put a little oil on both surfaces and smash they together "gently" they will be very hard to pull apart. Only then will they seal compleatly.

 

Why don't you save yourself a lot of extra work and just put gaskets on the exhaust manifolds to begin with. Henry Ford put exhaust gaskets on every flathead Ford that ever left the factory in Detroit! I don't think your theory is correct. A flathead engine has the center two cylinders both coming out of the same exhaust port together causing uneven exhaust flow and temperatures. An exhaust gasket costs very little. Why not install them and save yourself any future problems down the road!

 

I will use gaskets but which ones? The gaskets in the Fel Pro set look and feel like paper or use something like Remflex gaskets which are a graphite composite? The theory of no gaskets was not mine but have read it in various forums before.

 

They all work just fine . . . you're probably over thinking this just a bit!

 

Use gaskets. They allow for expansion and contraction of the engine heat cycle.
Easier on the bolts.
Plus, they work.

 

Agreed.