Originally Posted by cobalt327
That's why they pay me the big... ah hell, you know better!
Richard, what do you make of the size of the primaries on this deal? I remember you used your software to show the output using bigger long tube headers was close to the 1-5/8 headers, and this was on a milder build than a 500-plus hp/ 7500 rpm engine.
Mark, you know that I'm no scientist, I'm just an old hot rodder sittin' on a stump with a pencil and paper. The things that I don't know or don't understand scientifically, I try to figure out with common sense and what seems real to me.
When I was doing the sims, I found that the breakover for primary tube size was around 6000 r's on a 383 or larger motor. A 350 at 6000 would still make max power with 1 5/8" primaries, but a 383 at 6000 made a little better power with 1 3/4" primaries.
Here's how I would try to figure out what you're thinkin'. Let's say that a 383 at 6000 passes 665 CFM uncorrected for efficiency. We might conclude that somewhere around 665 would be the breakover point for larger primaries, since they make more power on a sim. Now, a 331 buzzed to 7600 would pass 728 CFM uncorrected, so it would seem logical to me to use a larger primary tube for more power at the top.
I might be full of it, but that's how it looks to me, sittin here on this stump.