square port header on round port w58m head?

[wilderb]

I just got a 620 and I am in search for more power I will be swapping in an L16 intake many ported for the right size head ports, topped by a weber 32/36, I also have a set of shorty headers but they are square port I am pretty sure that they will bolt up, but are they going to restrict the flow ? I want to install the headers so that I can also get rid of the stupid EGR crap, I will also be tracing the emissions related wiring and clipping them from their source in an effort to clean up my harness, any help would be appreciated

wilder

[datzenmike]

While a mismatched port header isn't optimal a round port into a square exhaust is better than the other way around. Why a header? They don't do much for any stock motor and are a lot of work to find this out. If you want a better flow get an L16/18 exhaust. It's basically a cast iron header.



I wouldn't run a smaller L16 intake on your L20B even if you 'port match' it the runners are still tight. Keep the L20B intake as it's much larger and will flow much better with the larger motor.

EGR? It's a myth that removing it will magically uncover or return lost hp. Just remove the hose from the carb to disable it and drive it. You won't notice any difference.

[okayfine]

I also have a set of shorty headers

Echoing Datzenmike's advice. Also, do you have a picture of your "header?" Almost all that I have seen are quite poorly designed and result in something they can market as a "header" but will do you worse in every way (performance, noise, heat, fit, and leaks) compared to the stock, cast manifold.

I want to install the headers so that I can also get rid of the stupid EGR crap, I will also be tracing the emissions related wiring and clipping them from their source in an effort to clean up my harness, any help would be appreciated

Keep in mind that while your 620 may be '75 or older, and you are not required to smog your car bi-ennially, you are still required under federal law to maintain all factory emissions equipment. I know, I know, but my suggestion isn't regarding disabling your EGR for whatever reason, but to suggest any effort to clean up your harness be restricted to taping up wires and not clipping them. Would be a PITA to redo all that work.