I have seen up to 11.5:1 with a big cam on a street LT1.

Rich

 

For the calculator that I showed you, it asks for deg ABDC + 15, other calcs may take that into effect, but this one asks that as the input.

I say obviously wrong, because right now the car is running pretty good at about 32 degrees timing, and with a 9.7 DCR, it would knock like mad on pump gas, when 9.0 is really considered the limit.

 

well I have a madz tune, mailorder so I dont know exactly where it is yet. ahvent driven it hard enough or had my scanner on it to see yet. I'll do all that as soon as I get back to work next tuesday.

and as for the deck height, yeah I meant .005-.007. I should just write it out. 5 thousandths. Im just retarded I guess.
so is my dcr pretty high? thats why it wont like alot of timing?

maybe I should start my own post so I dont hijack his thread anymore. hopefully atleast he's using my car as an example.

 

I ran 11 to 1 static on a 355 LT1 in south Alabama, its damn hot down here, and I would not say that 9.0 to 1 dynamic CR is the in stone cut off point for an LT1, If you are in a cooler overall climate and the cooling and fuel systems are up to snuff, you can go a smidge higher. And thats where the power is.


David

 

Im running 12.8 to 1 on my 383..I run 93 octane at all times but I do see 7-10 degress of knock..I plan on getting it tuned sometime since its been like that almost 2 yrs
My car is very, very streetable on the street...

Cody

 

There is not much difference in power from a few tenths gain in compression. The static CR needs to be set keeping the cam in mind, specifically the intake closing point ABDC, as has been alluded to. This is what determines the DCR. Beyond that, the available fuel is crucial. If your timing is being retarded 7-10 degrees you aren't gaining anything from your high CR!

Rich

 

But headaches wondering why the guy with 10:1 compression is running with your 12:1 motor...lol.

When I first put my motor together I used the impala head gaskets, I had a moderate amount of audible pinging going on, I had to watch how I drove, I even had to put extra expensive additives to keep my motor alive (best pump around here is 91). When I tore into it for various reasons I went back to the factory gasket, lowering my compression from 11:1 to 10.5:1 . The car was much easier to drive, the audible ping went away and 91 is fine. But that wasnt the real picture. I also changed cams from the 224/230 XE to the GM 847 cam (lowering the actual comp ratio quite a bit). I plan on this winter going again with the thinner gasket and according to my calcs it should be fine.