Ported and polished heads

livn

Registered User
I was thinking about getting my heads ported and polished, but the way the in take manifold matches up to the heads, to me it seams only right to have the manifold ported and polished as well. someone tell me im crazy and explain this.
 
porting heads

It's pretty safe to port match the intakes and even smooth out the bowls, but be careful on the exhaust side.
Don't port match the exhaust ports. Some of the best flowing heads are ones which they welded up some of the exhaust port making the exit smaller. The reason is that you want the velocity of the exhaust gases to be high and that will help to suck air out of the chamber when the valve opens. If your header or exhaust manifold is a big open circle and the head port is a smaller or D-shaped port, this will also help to minimize reversion. That's when exhaust gas bounces back into the port and actually creates more back pressure when the valve opens. Smoothing out the exhaust bowls (the area just inside the valve) is good but it's probably a good idea (unless you know a bunch more about it than I do) not to make the bowls much if any larger than the inside diameter of the valve seat. This is what I've picked up after wrecking a set of heads already. If this is wrong feel free to correct me. There seems to be a code of silence among the most knowlegable porting Yodas to keep their secrets.
 
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