is'nt that a lot of boost even for a 7.5 comp. engine on pump gas? how much boost did the stage 1 have?

Not at all. Not with that supercharger. You could run that boost with a 9:1 engine. I have done it many, many times. With a 7.5:1, you could probably run 17-18 psi of boost on 93 octane.
Eddie

Thanks Eddie for the response......

To figure this out mathmatically, you figure out the psi of the engine... one atmosphere = 14.7 psi at sea level ... therefore 7.5(compression ration) x 14.7psi = 110.25 psi cylinder pressure. Pretty darn low.... Add to that the 12psi the blower is introducing, and you come out with 122.25 psi for cylinder pressure... still very easy for 93 octane to control the combustion speed (no pinging). Effective combined compression ratio would be 8.32 to 1.

In Eddies example of 9 to 1 compression ratio, cylinder pressure would be 132.3psi, and the supercharger would add another 12psi to make cylinder pressure 144.3psi or about 9.8 to 1 total compression ratio. Still managable by 93 octane fuel.

So... with a 7.5 to 1 compression ratio, you would have to run aproximately 22lbs of boost in order to reach the combined compression ration of 9.8 to 1 that Eddie and others have safely run.

Short story... we are not pushing this motor very hard in order to acheive the horsepower levels we are at... it is just a good motor combination!

Hope this helps,

Chris

P.S. The boost on the stage I is 8-10 lbs. ... stock is 5-6 lbs

With That kind of pressure how long can head gaskets last

I am sure they are using Cometics. They will outlast the rest of the engine. I have yet to have a problem with a Cometic gasket. And I have really tried......1400+ hp and 50 psi of water pressure for well over 100 hrs.
Eddie

Why is it that a 525 with a whipple can make 775hp with only 7 psi of boost and a 600sci needs 10-12 to make 750hp? I realize that the 525 has a little more comp. and a little bigger cam. I'm not trying to secound guess any one but that still sounds little a lot of boost. My new nordic 28 is being built with the 600sci and i know i will need more power when the warranty is up but i don't think i would fill good about running that much boost on pump gas. How much boost does the 700sci have to make 700hp? The cam is only slighty bigger in the 700 over the 600.

chris and eddie thanks for all the info

Our 700 sci shows 7 lbs of boost on smartcraft at 5400 rpm.

Boy, you asked a whole lot of questions, all in a row.

The 525 has 8.75 to 1 compression, and a much healthier cam than either the 600 or 700.

The 700 requires 8-9 lbs of boost stock in order to acheive 700 horsepower (measured on two analog boost guages) at 5400 rpm.

You are underestimating the difference that the compression makes in these motors.

525 - 8.75 x 14.7 = 128.63 cylinder psi
600 - 7.50 x 14.7 = 110.25 cylinder psi
_______________
18.38 psi difference in cylinder pressure.

Chris

p.s. you will love the 600 in your Heat

Eddie what you think the Rpms will be on my 700 if I put the boost kit on with my stock harrings?

the 600 / 700 is way detuned. How about the NXT trans? What are they rated at and are they breaking? I have only heard of two; one being driver error and the other was in a cat that is run hard in rough water - never heard the real deal on why it broke.