how much comp to run in 572???

[badbug]

i have a 9.7-1 bbc 572 in 22 ft. stryker and i want to up the power a bit and i was wondering how much compression can i run if i mix 100 low lead av gas, 50-50 with 93 octane? I have dart 345 aluminum heads, roller cam, pro systems 1050 dominator on merlin x intake. Solid roller cam 114 lobe sep, 268-276 duration @ .050, .704 .704, 4/7 swap comp cams. Dynoed at 720 hp.
How much more horsepower would be made going from 9.7-1 to 11.5-1? Would you believe it will run 108 mph @ 6700 rpms like it is and im still not satisfied. What do you think?

[WETTE VETTE]

Adding a couple of points of compression will probably net you 25HP, which isn't worth the trouble of needing to mix you fuel in my opinion. You could probably do better by going to some CNC ported heads from Dart or AFR and keep it on pumped gas. I added a tunnel ram to my 10:1 598 and gained 4 MPH. Plus it looks pretty sweet and still runs on pumped.
Craig

[jdf]

i have a 9.7-1 bbc 572 in 22 ft. stryker and i want to up the power a bit and i was wondering how much compression can i run if i mix 100 low lead av gas, 50-50 with 93 octane? I have dart 345 aluminum heads, roller cam, pro systems 1050 dominator on merlin x intake. Solid roller cam 114 lobe sep, 268-276 duration @ .050, .704 .704, 4/7 swap comp cams. Dynoed at 720 hp.
How much more horsepower would be made going from 9.7-1 to 11.5-1? Would you believe it will run 108 mph @ 6700 rpms like it is and im still not satisfied. What do you think?so you are ready for plowman's this year

[RiverRacer]

Adding a couple of points of compression will probably net you 25HP, which isn't worth the trouble of needing to mix you fuel in my opinion. You could probably do better by going to some CNC ported heads from Dart or AFR and keep it on pumped gas. I added a tunnel ram to my 10:1 598 and gained 4 MPH. Plus it looks pretty sweet and still runs on pumped.
Craig
2 full points of compression will add a lot more than 25hp unless Cherolets don't burn fuel and pump air. RR

[WETTE VETTE]

2 full points of compression will add a lot more than 25hp unless Cherolets don't burn fuel and pump air. RR
With no other changes I doubt it, but lets just say it gains 50 HP from adding 2 points of compression. Still not worth it in my .02 when better heads and induction mods can net that much or more and be happy on 91 octane.

[cfm]

I agree with WV.
43.2hp would be gained if he received a 6% gain from the 2 points of compression. Let me re-amphasize "If."
Let's also remember that peak hp rpm will be reduced a few hundred rpm because of the extra compression and not changing anything else.
But, with two more pts of compression we can cam it accordingly to take advantage of the psi.
I'd go for head work and intake work (or TR) for some more mph. Then when not satisfying anymore go with more compression or more exotic stuff.
======================
Cool boat build BTW badbug !!!

[Chickenlips]

i have a 9.7-1 bbc 572 in 22 ft. stryker and i want to up the power a bit and i was wondering how much compression can i run if i mix 100 low lead av gas, 50-50 with 93 octane? I have dart 345 aluminum heads, roller cam, pro systems 1050 dominator on merlin x intake. Solid roller cam 114 lobe sep, 268-276 duration @ .050, .704 .704, 4/7 swap comp cams. Dynoed at 720 hp.
How much more horsepower would be made going from 9.7-1 to 11.5-1? Would you believe it will run 108 mph @ 6700 rpms like it is and im still not satisfied. What do you think?
Check your PM

[Sleeper CP]

i have a 9.7-1 bbc 572 in 22 ft. stryker and i want to up the power a bit and i was wondering how much compression can i run if i mix 100 low lead av gas, 50-50 with 93 octane? I have dart 345 aluminum heads, roller cam, pro systems 1050 dominator on merlin x intake. Solid roller cam 114 lobe sep, 268-276 duration @ .050, .704 .704, 4/7 swap comp cams. Dynoed at 720 hp.
How much more horsepower would be made going from 9.7-1 to 11.5-1? Would you believe it will run 108 mph @ 6700 rpms like it is and im still not satisfied. What do you think?
My .02 would be you would be fine doing it. Typically for every one point of comp. you'll pick up 4% in power, so all else being equal you "might" pick up nearly 50-56 Hp. But your trq. numbers will go up also. The best thing about it is the extra "pop" throttle responce you'll get with the added compression. I took my 565" Ford from 10.2 to 10.8 and noticed a difference, the cam I have liked it. Not that it used to be "lazy" but now when you step on it you feel it like "now". You certainley feel it with a two point jump. With the 114 lobe sep and 268-276 dur. cam You probably bleed off enough compression anyway. But you should call Comp Cams and ask for a "senior" tech guy, not some kid reading out of a book they we'll probably be able to give you a good answer. But if it were me, since I don't mind mixing gas I'd do it in a heart beat.

[cfm]

I picked 3% out of my butt. Where did you get 4% ?
Remember, rate of theoritical gain lowers as you start from a higher base #.
Gain from 8:1 to 10:1 will be much larger than 10:1 than 12:1. And that will be larger than 12:1-14:1 .

[Sleeper CP]

That 4% number is a number that has been floating around for sometime now, from articles and bench racers for some year. Last year EngineMasters magazine did a story on it(I'll see if I can find it) Steve Dulcich( if you Google his name you might find it) ran a 440 Mopar that he stacked head gaskets on top of head gaskets. I think he ran it from 9:1-12:1 if I remember correctley. He was trying to prove if the 4% number that he had been hearing over the years was true. Sure enough on his Mopar and engine combo the 4% rule was right on the money.
Yes, you can see more benifit from 9.5 to 11.5 then you will see from 12.5-14.5.
Here is something you might find interesting.Or then again you might already know this. I had a couple of friends that worked on "Cup" engines here in town, back when the "Cup" engines could run unlimited comp. and the "Truck" engines were limited to 9.5:1. The "Cup" engines ran about 300 degree's less exhaust temp on the dyno than than the "truck" engines,because the higher compression extracted more energy out of the fuel. Instead of it dumping out of the exhaust pipe it used it in the chamber to drive the piston.
Sleeper CP

[HammerDown]

Hot Rod Magazine June 2004 did a write up on the ZZ-572/720R 12.0:1
They backed off the timing 5 degrees and ran it (dyno) on 91 pump gas.
Cranking Compression 170 psi.
787 HP at 6,500 rpm 725 lb-ft at 4,600 rpm.
They noted, in general the Dyno was easier on a Engine then actual Drag Strip use.

[Cs19]

60 HP by bumping the compression, go for it.