max boost

[silverss]

Hello. I am building a 454 with an 8.2 to 1 CR and intend to use a Vortech Ysi trim without an intercooler. I wondered if anyone knew approximately what the limit on boost would be with 93 octane fuel. Thanks

[speedytang]

Depends on the heads. Are these aftermarket or factory heads. What are the cam specs because this matters also not just compresssion. Since I take it this is a Carb motor your limited because of tuning under boost. Start with 6psi which will probably be the limit till you run the motor on a Wideband.

[silverss]

The heads are Brodix aluminum. I don't remember the part # offhand though. Comp recommended a .660/.680 110 LSA i think; maybe a 112. The cam is a hydraulic roller. I don't remember where I wrote everything down at the moment; only had about 45 minutes of sleep in the past 40 hours

[speedytang]

When I input your cam specs I show you with a final compression of 9.25 based on a piston with a low dome. With 93 octane I just don't see you making over 6psi without retarding your timing so much to run 8-10 psi that you would make the same power at 6psi. So much to this but you really need to Dyno with a Carb and run a Wideband to shut it down if your getting lean between the primary and secondary opening. I had this problem on my Dual Paxton unit.

[silverss]

What would be the better carburetor to use with this setup; a mighty demon or a Holley 4150?

[speedytang]

I had some well worked Holley 4150's on my dual setup and converted to EFI because I could not get the mixture stable between the primary and secondary opening. I was building this for a boat and carb is easier and better when out on the water but to much time invested when a Ford SB can be EFI so much easier. I have heard excellent results with the Procharger guys using the Demon.

[Stroked-Z]

What would be the better carburetor to use with this setup; a mighty demon or a Holley 4150?

Contact CSU for a carb that will work with a BLOW-THROUGH application....

its what i use & many others http://www.csucarbs.com

-Carm

[stevieturbo]

Will the YSi be able to shift enough air for you to reach the limits with a low CR like that, a big cam, and a big engine ???

Im making 19psi at 7000rpm in my 382 LS1, Edelbrock 215cc heads, 224/230 on 115LSA cam, 8.5" crank, and 3.0" blower pulley
On 8.7:1 CR, mines fine on pump fuel.

Slippage aside, thats spinning the blower pretty damn hard ( 12 rib )

[silverss]

I'm not sure- I've never built a blower motor before. Vortech offers the Ysi as the universal big block kit. I actually decided to go with a Merlin block so it will be a 509 instead of a 454. I really just want to build something that I can drive anywhere and will last a reasonable amount of time. Vortech says the optimum compression ratio is 9:1 with the supercharger; should I stick with around an 8:1 or bump it up to a 9:1? I've been talking to Comp Cams about cams and what their recommendations are. There are too many decisions to make!