ChevyNo1

I'm just wondering how much timing ( on 91 octane ) I could run on this combo . . . on the stock motor I was running around 17 degrees . . . shouldn't I be able to bump this up? I'll probably run 10psi on the turbos, which is probably when they'll max out.

- Dug

MECHAM

iTrader: (4)

i thought how much timing was based on IAT's and octane?

i wouldnt push too much timing on 91 octane.

if you dont mind...could you list the specs on your engine..thx

bore
stroke
piston reliefs
gasket thickness
deck height

ChevyNo1

Well, you are correct, but the CR of the engine will play a BIG part in the equation as well . . . stock CR on a 346ci ls1 is 10.1:1, I'm dropping to ~8.9:1.

This is essentially a 6.0L ls1, .030 over. That makes it a 4.030 bore, not sure on the stroke though. The reliefs on the pistons are -15cc . . . stock gasket thickness, not sure on deck height.

- Dug

MECHAM

iTrader: (4)

hmm...

your stroke has to stock 3.622
stock head gasket height .052

according to here http://www.rosspistons.com/calculator.php
the deck height will need to be known...but according to my numbers it looks like
369.61 cubes
8.66:1 comp

8.66 is a long way off from 8.9 - could mean an extra psi on pump gas or 1-2 degrees more timing with 91. best to know exactly what the C/R is...IMO

4.030
3.622
73
.052
.0001
-15
8

i thought c/r was to dictate how much boost u can run on pump gas?

i dont know either...im piecing all this stuff together to...some1 with some knowledge will chime in..

ChevyNo1

Thanks Mecham . . . interesting . . . APE told me with 73cc I'd be around 8.9:1 . . . but I see you are right, the calculator says otherwise. I will speak to APE again about this. Although I'd rather be LESS than 8.9:1 than above!!

Yea, the lower the CR the better for boost, to a certain point. Too low and it can get doggy in the lower rpm's . . .

- Dug

verbs

APE goofed on my compression ratio calculations by using the wrong gasket size in their calculation. They said it was going to be I think .41 or something like that when it was really going to be .52. I might ask them what gasket size they used in your calc.

MECHAM

iTrader: (4)

stock gasket is .052

i think felpro is .041

since he is going turbo...lower of course is better 8.66 isnt too bad...but if they goofed the other way...and gave him 9.1 +

Pro Stock John

iTrader: (34)

I'd start off with low timing, and bump it up either on the dyno or on the track but a little at a time. How effecient are the Incon intercooler? What do the IAT's do on a full dyno pull?

ChevyNo1

Thanks Verbs, I'm gonna call them today . . .

PSJ, they work quite well . . . but I honestly can't remember what the IAT's were the last time I dynoed . . . I know on the freeway going from about 40mph - 120 they only rose about 30 degrees . . .

- Dug

Slowhawk

iTrader: (12)

Matters on how efficient your intercooler is on how much timing you can run safely.With that compression and an efficient intercooler you could run 22-24 degree's on timing across the mid and pull alittle out on top end.Of course A/F should be around 11-1 for this.

ChevyNo1

Just checked some old logs . . . 2-4 gear runs on the freeway in November ( AZ, prolly about 55F out ), my IAT's went from 102 to 126 . . . so only a jump of 24F.

- Dug