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Thanks all. I know the cam has 4* of advance built-in so the centerline is 108 right?. I'll try some calcs at 108 ICL
So if the ICL is 108 then your DCR with the 9.8:1 heads would be 7.76:1 and with the 10.3:1 heads it would be 8.15:1. Your advertised ABDC would be 67 degrees.
Just in case anyone is interested in how I got that.
Advertised intake duration / 2 - Intake Centerline = X + 180 = Y
Advertised intake duration - Y = Advertised ABDC
So if this is the case and this is a street car I would probably go with the lower compression heads. I'm not 100% but they probably flow better and would be more pump gas friendly. Not that you couldn't get the higher compression ones to work. But getting it tuned properly would be more critical.
Last edited by Phobos84; Sep 21, 2024 at 04:25 PM.
So if the ICL is 108 then your DCR with the 9.8:1 heads would be 7.76:1 and with the 10.3:1 heads it would be 8.15:1. Your advertised ABDC would be 67 degrees.
Just in case anyone is interested in how I got that.
Advertised intake duration / 2 - Intake Centerline = X + 180 = Y
Advertised intake duration - Y = Advertised ABDC
So if this is the case and this is a street car I would probably go with the lower compression heads. I'm not 100% but they probably flow better and would be more pump gas friendly. Not that you couldn't get the higher compression ones to work. But getting it tuned properly would be more critical.
What a great education. Thanks. My buddy will likely not want tuning and reliability on his mind. He's just going to want to drive...and I think he prefers the AFRs anyway.
I would probably go with the lower compression heads. I'm not 100% but they probably flow better and would be more pump gas friendly. Not that you couldn't get the higher compression ones to work. But getting it tuned properly would be more critical.
I agree with this assessment. And the AFR heads have the best valves, springs and hardware available for a street engine.
Here's a dyno chart from John Lingenfelter's Modifying Small Block Chevy Engines book. This engine has 9.2:1 compression, ported 113 heads and his LPE 219 cam which is a single pattern 219@0.050 and 0.525 lift 112LSA. Peak numbers were 442hp and 481 ftlb torque. Your engine has more compression, a little more cam and better heads. You should be above 450 HP and 500 ftlb torque at the crank. You'll need a free flowing exhaust and a good tune.
Look on YouTube for Richard Holdners TPI Mega Test. It's one of the most comprehensive 383 dyno tests I've ever come across. His test engine has a more aggressive cam but you can glean a lot of useful info from all the data.
I agree with this assessment. And the AFR heads have the best valves, springs and hardware available for a street engine.
Here's a dyno chart from John Lingenfelter's Modifying Small Block Chevy Engines book. This engine has 9.2:1 compression, ported 113 heads and his LPE 219 cam which is a single pattern 219@0.050 and 0.525 lift 112LSA. Peak numbers were 442hp and 481 ftlb torque. Your engine has more compression, a little more cam and better heads. You should be above 450 HP and 500 ftlb torque at the crank. You'll need a free flowing exhaust and a good tune.
Look on YouTube for Richard Holdners TPI Mega Test. It's one of the most comprehensive 383 dyno tests I've ever come across. His test engine has a more aggressive cam but you can glean a lot of useful info from all the data. https://youtu.be/B3Je1MLTphs?si=q0P5PMsPv_H6FG6F
