My question is what compression are you save with at what boost.
I presently have a fully forged 383 LT1 that has 11.2 compression.
I have an opportunity to get a supercharger that will deliver 4-6# boost without intercooler.
Do you feel that a forged bottom end with my compression would last or should I be looking at decreasing compression. Is there a rule of thumb that you use to calculate this issue. I am trying to get around having to remove my motor, buy new pistons, and rebalance the entire assembly.

 

With a fully forged bottom end, you might make it a while as long as you keep the boost that low - methanol injection or something would also help.

But your compression is way too high for running much boost at all. 10.0:1 is about the highest you see people go on blower motors, but around 9.0:1 is about normal. IMO - you should just run a nitrous shot on your motor as it is now if you dont want to lower the compression. If you want to go for a blower, I would lower the compression first - because once you feel the boost, you will always want more!

 

also, that "4-6#" -- is that on a stock engine? If you see 4-6psi on a 350, you won't see that same pressure on a 383. Maybe 2-4psi.

 

The issue with a high compression engine is that you'll have to run high octane race fuel to prevent detonation issues. Lowering the compression ratio will allow you to boost the engine and manage detonation with 91 -92 octane.

 

Agree with above posts. If you run a VERY mild application of boost (4#'s or so), with methanol injection, on a fully forged setup, you will probably be okay. But for the little extra power 4-6#'s will do, it would be much more cost effective to make power using your existing high CR forged motor with Nitrous.


If its a matter of HP, you need to ask yourself, which you want more;

550 RWHP with Nitrous for $2,000 (top of the line direct port setup) using current motor?

or

550 RWHP with a blower for $18,000?

 

If you want to use pump gas and drive regularly on the street, seriously, don't boost it! On the other hand, if you don't mind using race gas, intercool it and add as much boost as the octane will allow, and be safe with your timing.
Steve

 

I'm not big on nitrous as it is generally addictive until disaster occurs.
My car presently runs 11.40 NA and 3825# with me in it.
I thought a little boost might get me into the 10's.

 

That is interesting to note as I didn't realize boost decreased with inches.
That being said 2-4# boost probably wouldn't help much especially if I have to pull timing out.

 

Also dont forget about the 70 extra pounds of weight for the setup.