Exhaust manifold

[STEVE1103]

400 Chevy I am installing has round exhaust ports, the exhaust manifolds in the car have square ports, will they work or do I need new manifolds?

 

[zzrodder]

If the round port is no bigger than the square manifold ports, no problem. If the port in the head is larger, it will hurt flow somewhat, though if you're using cast manifolds you can always match them to the head ports with a little work with a carbide burr. Check that the manifold flange and the raised flange around the ports are not mismatched so that there too narrow a sealing surface that will cause them to leak.
Headers will give you more HP and there are many port shapes available.

 

[Crossfire]

exhaust ports.

You need to match round to round,square to square or all you will be doing is changing exhaust manifold gaskets regularly and restricting exhaust flow which does effect performance.Also what gasket are you going to use for the setup,there is no 2-way gaskets out there.

 

[NitroJohnny]

If the exhaust manifold port is smaller you will get back pressure and be buring up gaskets pretty quick. You can always open up the manifolds to match the head ports. ISnt too hard if there is enough meat to do it. You may also do some research to see if someone makes an adapter for what you are doing. There just might be one.