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Exhaust port design


CCCUK Member
Oooooh, first post!!!

So, I have a ‘70 C3 with a replacement ZZ4 engine, which has a block stamped from the mid 90’s and I am in search of replacement headers. In the process of doing so I’m beginning to suspect that it was a short block kit (engine base without cylinders, heads etc) rather than a complete long block kit. Specifically because the exhaust ports I have are square (typical for a C3) and every header I can find for mid-90’s Chevy engine has round ports.

As I only have my hodgepodge vette to compare with, can anyone help identifying what headers I should be buying? What shape ports do you have on your C3 and C4s?