[71 Ventura II]

Originally Posted by 462ta

Ventura--is 30% drivetrain loss really that accurate with a TH350 most ive read or talked to said more like 20-22%, were going to put the car back on the dyno and do some tuning before i tear anything apart to see if we can find some HP, sticking witha quadrajet so im going to find/borrow couple diff set ups to quicken up the down times.

The Inverse of the loss is what's used. I did not use a loss of 30% but did use 23% by using the inverse factor of .77. Ex. 386 HP X .77= 297.22 RWHP.

As a general rule I use parasitic losses of 23% for traditional 3 speed automatics and 15% for a manual transmission applications. Use inverse of .77 for auto and .85 for clutch. (As a disclaimer some of the lock-up automatics can be slightly more efficient and the exotic race clutches can be extremely efficient but for the norm these are good "Median" numbers to work with).

FWIW I would speed up the timing curve or lock it between 34-36 degrees. Keep in mind with the lower compression and unknown "squish" or "Quench" area for the combustion don't rule out more total timing in the 38-40 range and conversely trying 32-34 if the return is not rewarding while increasing total. I'd speed up the curve and try adding one degree at a time until the power drops off then back up.
WARNING: If your distributor does NOT have positive stops installed to limit the mechanical advance above 4000 rpm's it will kill your HP!!! Without the stops the springs will stretch allowing additional timing sometimes 7-10+ degrees! If you don't have it limited get it done ASAP. JD