It was suggested to me recently that maybe my compression was a little light @ 9.2:1, and part of the reason for not making better #'s. Everything I've always been told and learned, from Magnusson itself to various builders suggested it SHOULD NOT be higher than 9.5:1 and that 9-9.2:1 was perfect.
What's everyone else running?

 

I run 9.9:1 with the 112 and I would venture to say that most other applications run 9.5:1, the stock CR on the LS engines with the exception of the LQ9 and L33. It does seem that the positive displacement blower likes the compression a little higher. What kind of power are you making?

 

I would run somewhere around 10-1 compression. People put Maggie's on the LS2's all the time and they have 10.9 compression.

The front drive / rear inlet Radix design does not have the advantage of overdriving the blower with the jackshaft. Most Radix 122 set ups I have seen have struggled to make more than 10# on 5.7's and 6.0's.

 

Still sub 500rwhp/torq @ 8lbs/100% meth...but I've had ongoing IAT issues that have prohibited me from boosting up. Thing is, my CR was what the manufacturer kept telling me I needed...seems I've been sleeping cause now I'm hearing diff on here. I'm about to change rods and rockers, and I have stock gaskets...will I have to change heads to get compression up? Can they just be milled maybe?
Either way, trying to determine if this is really gonna help scavenge more ponies - and enuf to matter?

 

I am running 10 to 1 on the 370/LS2 TrailBlazer SS and the 427/LS2 SSR has 9 to 1 compression. I like the higher compression on the 370 build and the lower compression on the 427. The 427 has so much low end torque that you dont notice the drop in compression. We are going to tear back into the SSR for a WCCH L92 Head swap with more boost. I am wanting to have the SSR with around 13-15 psi of boost on street gas.

You could always swap the heads out for a set of the WCCH LS2/6 243's to up the compression if you are currently running the 317's. I really dont like to mill the heads in a build that will see boost or nitrous. The thicker the heads deck surface the less prone to warp. I have a stock set of 243's here of my TrailBlazer SS's LS2 that I would sell real cheap. They only have 2000 miles on them and would be perfect for a CNC job from WCCH. I could even ship them to Richard for you.

 

Right now I have AllPro 236/66...What do think I cud expect to see it I made this change? I'm frankly a little annoyed with Mag, as I didn't come up with 9.2/9.5:1 on my own - that was their suggestion! I'm a little tired of spending my cash to do their R&D...R/

 

Just stick to the pm's unless you want a thousand answers.

R

 

Dont get me wrong, you can make the package you have work. The 8 groove pulley setup and more boost will make up for the lower compression (you should be able to run 10 psi on that compression with street gas). I dont think you need to spend more money right now. I think that maybe a few changes with respect to the heat exchanger and meth should have you where you want to be. Where do you live? Do you have a custom tune and are you using a MAF or 2 bar/SD?

What are you spraying in the Meth setup (50/50 or straight Meth)?

How are you spraying it (what boost level do you start and how much)?

What do you have for Heat Exchangers?

 

I live in CT, 2bar custom SlowHawk tune, 100% meth @ 4.5lbs, on the Mag122 heat exchanger kit. Prob is that when I spin it up any higher KR becomes an issue and its just a heat soak. Now since I've droppped some of my temps recently with a few tweaks I've made I might be able to bump it up now...waiting for cooler temps to do some tuning. My debate now is, do I keep fighting against the obvious limitations of the Mag, or just bolt on a turbo - and maybe get gobs more power on the same base set-up.

 

Here ya. R/