Originally Posted by huge496
Anyone here done any porting or flowing testing on the small valve Pontiacs? Anyone done any dyno or track testing with a ported small valve head compared to large valve heads? I assume that some testing has been done at one time or another, or does everyone just assume that the larger valve heads work better in every case.
the 455 engine I have in my car now came out of a 1971 station wagon- I found it in a local junkyard still in the wagon, with a 2-bbl intake on it- and low CR, big chamber, small valve heads
just for the hell of it, I took those heads, milled them .065"- put 2.19" Cleveland intake valves in them- and cut the exhaust valves down to 1.74" to fit
scribed the RA IV intake gasket pattern on the intake ports, opened them up to that size, and feathered it back into the port some- also widened the port at the short turns into the valve bowls
the resulting intake port is now 155 cc, the same size as a stock big-valve 400 head
flowed them, they flowed 230 intake, 180 exhaust- which is a little better than a stock big-valve D-port
basically gained about 20 cfm intake/exhaust- they can be ported much more than what I did
the intake valves were cheap, $5 each from PAW
I have not yet run those heads on anything, they sit gathering dust. Basically it proved you can put money and lots of time into an iron D-port, and gain very little- why bother when an E-head flows 290 cfm with no porting
and the CV's will flow nearly 400 cfm...
the iron D-ports are for someone on a very, very tight budget, these days...