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you get
8.2 DCR, using the KB method nets 8.8....it should run fine on 92 or 93, you may have to be a little conservative with your distributor's timing curve.



Does this number take into account his altitude? If not, he's going to end up with a DCR of about 6.5 and a SCR in the high 7s.

And, I don't like the cam... the ramps are too slow for a roller. Get something in the 35º range using the .050" numbers.

ETA: I did some rough calcs using 60º as the ICA, a 10.5 SCR and 6000' of altitude. Your cranking pressure is only 140 psi. That's not going to get it done, Frank.



either way, the compression RATIO is the same, it's just the CYLINDER PRESSURE that's lower at altitude.



Exactly! What I'm trying to emphasize here is cylinder pressure is critical at higher altitude. For example, if 165 psi is the limit for 91 pump gas at sea level, then that is the target that should be hit @ 6000'.


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also, you can't judge a cam's aggressiveness just by the advertised and .050 numbers. Hydraulic rollers a lot of time "look" less aggressive becasue they usually have slowish opening ramps.



I acknowledge rollers are more efficient and do promote higher VE. But, you can't build a 10:1 SCR sea level engine and expect a roller cam alone to make up the 25% loss @ 6000', and we haven't even brought up DA which on some days will be 8,000'-10,000'. Personally I haven't seen any empirical data that quantifies a given percentage increase in VE over a similar solid cam. But let's say there is a 5% increase in cylinder filling using the roller. It still leaves the OP way short on cylinder pressure if he is starting out @ 140psi.

Also DCR is not a panacea. Sure at lower rpm it's a factor, but once the revs go up SCR becomes the dominating factor.