Originally Posted by HaxbySpeed (Post 3552731)

You'd have to stray pretty far from the norm, like running a straub cam, to really screw up a basic blower deal.

Originally Posted by Young Performance (Post 3552716)

Thanks Thunder. I'm glad you understand. However, you're running with Hyper-u-crackit pistons????
You're braver than me:lolhit:

But, there's no arguing (at least, for most) with success. If it works for ya, stay at it.
Eddie

Originally Posted by Panther (Post 3552734)

Agreed, thanks for sharing!

Mine is;

"Your engine summary is as follows: Bore 4.53 inches, stroke 4.5 inches, rod c-c length 6.7 inches, with a static compression ratio of 8.3 :1. Your camshaft specifications call for an inlet valve closing of 54 degrees ABDC (after bottom dead center).

Your chamber volume is 162.81 cc's. With this camshaft your dynamic, or effective stroke is 3.82 inches. Your dynamic compression ratio is 7.20 :1 corrected for cam timing, altitude, and rod length. Your dynamic cranking pressure, corrected for cam timing, rod length and altitude is 138.55 PSI. Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and 7 PSI is 10.63 :1."

To add, I see my cranking pressures usually pretty darn close, within say 5-7% give or take.

Originally Posted by HaxbySpeed (Post 3552731)

Just like Eddie's 190 psi works for him with his cam selections, obviously the IVC is bleeding enough pressure to get down to the 155 pumping range. You'd have to stray pretty far from the norm, like running a straub cam, to really screw up a basic blower deal.

:

Originally Posted by blue thunder (Post 3552792)

Actually if you look at the original calculator we are discussing, it uses abdc intake valve close * to calc the cranking pressure we are talking about.

Originally Posted by blue thunder (Post 3552790)

Something seems wrong there bra, 162.81 cc chamber volume??? I don't know, I run small 454 junk :o).

Originally Posted by Panther (Post 3552888)

Ya got me, I just plugged in the numbers they asked me for and that's what it spit out. I'd have to assume the chamber volume is the cc of the head, plus the dish in my pistons and then a head gasket etc??? If I were add all those cc's together it doesn't seem that far off??

Originally Posted by blue thunder (Post 3550582)

I run the 525sc blowers with 3.25" pulleys and make 6.2psi. Edelbrock rpm performer heads. 9.5:1 compression on 93 octane. Much care is put into my engines though to ensure the setup is right (quench, a/f, timing, valves, mls, ect. so that may be a little much for you. Certainly 9:1 on 91oct, 30* all in, 11.8 wot a/f and a cool running alum headed engine would be doable (12.7:1 dynamic). To be aggressive, last season I ran 9.6:1 compression and 6.2psi for a 13.4:1 dynamic ratio. Rule of thumb is supposed to be 12:1 total but I have debunked that, at least with my junk. This year I am going to add a bit of margin and run 9.4:1 with 6.2psi on 93oct.