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Old 08-24-2009, 03:13 AM
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First, let me say that I've had enough feedback from several different sources including professional engine builders who flow these heads in the real world to convince me that flow figures published by head manufacturers are pretty much bogus and are inflated in order to sell heads. Since I don't have the facilities to flow each head before I enter it into the DynoSim software, I've decided to factor published head flow by .90 in an attempt to approach reality. I'll post that caveat on each DynoSim pull that I do from now on, including this one for you.

Now, with that said, it looks like you'll need more head to reach 500/500. On a brighter note, I don't know if you chose the cam for this combo, but if you did, kudos to you. You nailed it. I couldn't find any more power with less or more cam on this DynoSim pull.

It's a shame that Edelbrock hasn't stepped up to the plate with the RPM-XT head for the small Chevy. They have it available for the 351 Ford, but not for the SBC yet. That's the head that a 383 needs.

Using 64cc heads, 6cc's in the piston crown, an 8cc gasket and zero deck, I calculated a 11.05:1 static compression ratio for your build.

THE PUBLISHED FLOW FOR THESE 60899 EDELBROCK RPM HEADS HAS BEEN FACTORED BY .90 FOR THIS DYNOSIM PULL.

RPM HP TQ
2000 145 380
2500 184 386
3000 235 411
3500 296 445
4000 355 466
4500 404 471
5000 442 464
5500 460 438
6000 448 392
Peak volumetric efficiency 99.5% @5000
Peak BMEP 185.7 @4500
1.6 rockers on both valves will only add 6 hp, so I wouldn't think it would be worth the extra stress on the valvetrain.

Just because I like doing this, I ran the numbers on the RPM-XT Ford heads and factored them by .90 as well, figuring that when Edelbrock releases the Chevy head, it will be close to the same flow as the Ford...I used the same cam as above...

RPM HP TQ
2000 144 381
2500 183 384
3000 236 414
3500 303 454
4000 369 484
4500 427 499
5000 473 497
5500 499 476
6000 506 443
6500 477 385
Peak volumetric efficiency 104.7% @5000
Peak BMEP 196.5 @4500
It's clear that your combo needs more head.

Last edited by techinspector1; 08-24-2009 at 03:19 AM.
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