318 head porting for the average joe

Badart said

Justin would it really be worth it to clean up the runners, valve guide boss and bowl area on these 318 heads in my other thread if I use the factory 273 exhaust manifolds. It does have duals running all of the way back. Would the increase in flow help make up for the compression that I will be losing by swapping to the open chamber heads?

The only reason why I would run them is because they are fresh, super cheap and have hardened valve seats. I have to tear them down anyway and install new valve stem seals anyway.

Click to expand...

Well of corse it'd help, manifolds or not, do the angle smoothing and guide shape, it's safe, u cant really screw up if you take you're time at slower grinder speed. look at the 1st page of this thread.

At the very least...
cc them heads, then just have them milled=60 bucks.. and u wont be losing any cylinder pressure and it will be a win by virtue of good sealing valves.

as for the last question..lol...you gotta consider the rings, if they are not sealing 'more blowby from more cyl pressure' and say the the cyl pressure is way down already=110'lbs....dont expect a lil more flow to cure the loss of power once u start burning oil ...and again, measure both chambers of the 2 heads...and u can figure the diff and get a rough idea

if it were me, i would have done a leak down test before the old heads came off.

every 5 cfm is said to give 10 hp increase, that is if the cam works at the lifts flow increase.

what do u think? ;)