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Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
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Quote:
Quote:
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.
no, I just plugged the IVC point in the calculator. the calculator doesn't account for altitude/air pressure...either way, the compression RATIO is the same, it's just the CYLINDER PRESSURE that's lower at altitude.
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.
for comparison, let's compare this cam to some hydraulic flat tappets, looking in the comp cams master lobe guide
the comp XE274's intake:
274@.006" dur, 230@.050 dur, 143@.2" dur, .325" lobe lift.
the XE275HL's intake lobe has these specs:
275@.006" dur, 231@.050 dur, 149@.2" dur, .35" lobe lift.
it looks like the cam he's looking at is using comp's XFI lobes, which are amongst the most aggressive hydraulic roller lobes I've seen, and which according to the catalog spec like this for the intake:
274@.006" dur, 224@.050 dur, 149@.2" dur, .358" lobe lift
so for a given .006 duration, the roller has 6 & 7 degrees less than the .842/.904 dia flat tappet lobe, but 6 degrees more, and the same .2" duration, and more lift than both....I'd say that's an aggressive lobe.
lets compare to some solids. can't directly compare advertised numbers, since comp uses .015" lift duration as advertised duration for solids. let's compare to a .842" dia XE solid lobe, which looks like this:
rated dur (.015" lift), .050 dur, .2 dur, lobe lift
262/224/135/.319"
274/236/147/.335"
so it looks like the juice roller's lobe is more aggressive than an aggressive .842" solid flat tappet lobes in terms of .2" dur and lift compared to .050 duration......
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