[DaleO]

I have just completed a compression test. It is interesting in that it involves the same short block but two different heads. There is nothing earth shattering or anything, we all know that when we put larger chamber heads on we'll see a lower compression ratio, but we like numbers so....

The short block is a 0.030 over 428 with an Engle cam p/n 2618H, 260/268 adv (yes two six zero/two six eight), 216/226 @ 0.050, .305 I lobe, .310 E lobe, .458 lift/1.5 and .468/1.5, 112 degree.

The first test had 62's pretty much stock and resulted in 212 psi, explaining the need for mixing race gas.

The second test with 6X-4 by Dave Bisschop resulted in 167 psi.

Some supportive info from the 1967 manual indicates 150-170 psi is around 8.6-9.2 cr and 185-210 psi is around 10.5-10.75 cr.
Some supportive info from the 1974 manual indicates 120-160 psi is around 8.0-8.4.

From other tables I've figured I'm at 9ish cr and this data seems to add up pretty well. So I'm calling it 9 to 1 cr and ask you help for a camshaft recommendation considering a couple significant upgrades since the 62 configuration. I believe there is probably a cam which better compliments ported 6X's and the TSP stall convertor which brake stalls at 2,500 rpm and flashes around 2,700/2,800.

The 6X-4 heads flow as follows:
intake
218 cfm at .400 lift
237 cfm at .500
245 at .550

exhaust
168 at .400
179 at .500
184 at .550

Maybe the cam I have with 9:1 is sufficient, but if not, I'm open to suggestions!

edit to add rear ratio. I have 3.23's right now but I am about to the pull the trigger on a new rear and am deciding between 3.50 or 3.60.