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Ok it has been forever since getting any garage work done, and the daughter's Monte is still looming in front of me. Went to put engine and tranny together and found out I had wrong flywheel, and hence, starter. Anyway, got that problem resolved, but now I have people telling me that my headers are the incorrect style for my head exhaust ports, and that I need different headers. I have some other friends that say buy the exhaust manifold gaskets that match the heads and bolt up the headers I have and everything will be ok. Others say no, that set-up will leak. None are experts, so I thought I would turn to the Forum tech/performance experts. Engine is a 86-91 305, tranny is a turbo 350 and it is all getting stuffed into a 77 Monte Carlo. Pics below.
Port size is the same side to side but top/bottom ends are ovaled and different for the headers. Any help would be great. And once we get this done, we can get back to the Vette!
I would look carefully at the top-bottom dimensions of both the head and header ports to see if the ports are going to seal.
You could take a piece of poster board and using the head port, create and exact copy of the machined surface of the port opening. Spread some dye over the header port and place the "gasket" over the port on the header and see just how much overlap you have. Post the results here and I'm sure you'll get a more productive response.
A quick measurement will tell you. But the header tube is shaped like that to allow for the bolt holes. The larger the tube, the more it will appear distorted.
As long as you have the gasket squeezed between the header and the head, and it seals you do not have a problem. If the head port is bigger than the header opening this will increase your back pressure and decrease horsepower. If the header opening is bigger the head port there will be a slight turbulance in the exhaust flow d the headers will not preform to there max abilities. The will not be any exhaust leak as long as the gasket material is squeezed between the head and the header.
Will these headers work?
