Quote:
Originally posted by Gunter
What numbers can I expect with this SS 3.2 I just finished:
Bottom is from an ’82, mild boat-tailing, standard 70.4mm crank.
CIS is from a ’78 with the larger intake runners.
Heads are ported to 39mm.
98mm P/C’s, 9.8:1 CR, CIS dome.
Cams are 964.
SSI’s with an M&K muffler.
I am keeping CIS and Bosch CDI.
What’s your guess? HP? Torque?
I
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Sounds like a good engine. I agree with some others that HP figures are often misquoted and many chassis dynos appear to be a bit optomistic.
Remember that Porsche themselve, back in 74 with the 3.0 RS found that an MFI motor with the big overlap "S" cams and the old style tuned exhaust (equivalent to SSI's) needed a 9.8:1 compression to make 230 DIN HP, about 220 SAE net FWHP, I assume local Dynos should be measuring SAE net HP, not DIN.
A late model ROW 3.0 CIS with 9.8:1 pistons like yours made 204 DIN HP (~195 HP SAE net). Does anyone believe that with an SSI exhaust, CIS instead of MFI, softer, no overlap cams, that an SC engine will make 220 FWHP like the 3.0 RS motor made?
I don't. Let's be very generous and say it makes 215 FW SAE net HP and that the MFI and S cams are only worth 5HP. Then I'd guess gunter could make 7% more, or 230 SAE net FWHP (~195 RWHP)
Also recall that Porsche themselves didn't even pick up 15 when they boosted the Carrera RS 2.7 motor up to 3 liters until they upped the compression from 8.5 to 9.8:1.
Regards,
Jerry Kroeger
I would use that as my target for your motor. You've got much less radical cams in you engine, but you've had it boatailed and boosted the displacement by almost 7%
Had to edit some typos...