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Discussion Starter · #1 ·
Hi everyone, I've got a 396 with 9.7:1 static compression that I want to bolt a 6-71 to. It has a Lunati 402A2 solid flat tappet cam .550/.570 238/248 @ .050 272/282 seat, 112* lobe separation. The short block was in the car when I bought it and I really don't want to put any more money in it. The plan is to pick up a 454 HO crate and a set of AFR 305's over the winter but I would like to use the 396 for learning purposes before the 6-71 gets bolted to the new parts. Question is, how much of a grenade am I creating?

The motor has small 100cc chamber 290 iron ovals that I had bigger valves put in when I did the cam. Would it be worth it if I could find a cheap pair of large chamber iron ovals in usable condition to get me through? I'm just getting kind of old to be humping iron BBC heads across fenders. ;)

-Matt
 

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Since I don't know anything about your motor or blower I will throw some numbers out there for your reference. These are text book calculations and real world will vary a little.

At 9.5 static CR and 10 psi boost your effective compression ratio (what the engine thinks the CR is) will be 16 to 1. You'll need some pretty good gas and timing controls for it to not detonate itself to death.
Drop your static to 8 to 1 at 10 psi boost the effective cr will drop to 13.4 to 1.
Does that help?

Blessings........Ron.
 

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Discussion Starter · #3 ·
Yeah I kind of figured as much. I was only looking for about 5 or 6 psi and wondering if the cam bleed off would help any. Looked like it might be doable from the chart on BDS's site. I may have someone interested in buying the 396 now though so it may not be an issue.

-Matt
 

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Years ago I did 9.5:1 with 7 PSI and a B&M Powercharger 250 on 93 pump gas.

36 degrees locked out timing, then pulled out 5 degrees at 4+ PSI.

Ran 11.20s with stock leaf springs, 11" slick, and no traction devices, at 3700 lbs.

If you could find a set of 049 heads with the 119CC chambers, what you have will work well.
 
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