Oldscoolnew

Hey guys I have a question regarding my Camshaft and DCR. I have a lq4 block and 799 heads. Heads are at the machine shop now, he just did a clean up pass on them .04 or so. I should be around 11:1 comp ratio. The cam I went with, now im not married to it if its going to be an issue i will get another, the cams a
Comp LSR 269lr hr12
269 277
219 227 @ .50
.607 .614 112deg
inlet valve closes ABDC 62 deg
I used wallaceracing.com DCR calculator with my elevation being 850ft and My Comp ratio at 11:1 came out to be 8.79:1 DCR is this going to be an issue with detonation or other problems? Considering that I have a proper tune. What do you guys think ?

AutoCruzer

Be careful with the Wallace calculator. You would be better served by the uempiston calculatoe which takes chamber size and other factors into account. The Wallace will get you a ballpark number if you already know your static compression. Even then, it is still dubious.

speedtigger

iTrader: (16)

I ran 10.9:1 with a 222/224 on 112 with 110 ICL and it was not a problem. I can't remember what the IVC was.

yonerhottlt1

iTrader: (21)

Since when does 799 heads with a 4 thou cleanup on an LQ4 make 11:1 compression anyways?!

speedtigger

iTrader: (16)

I did not see that part. I would say it does not. On an LQ9, yes.

AutoCruzer

Those cam specs definitely suggest lower cylinder pressures.

Oldscoolnew

I rebuilt the bottom end with speed pro flat tops thats how I came up with 11:1. I called comp they said I'm going to have an issue with that cam recommended and xer grind 232/234. I'm going to give Texas speed a call. I redid the dcr calculation with the uempiston program and it came to 9.04

speedtigger

iTrader: (16)

Yeah. I don't remember for sure, but I think the IVC was around 66 to 68.

S10xGN

iTrader: (11)

Are those IVC numbers @ 0.004"? Cause I have an unknown cam that I "cam doctored" myself and the IVC is 35° @ 0.050"...

garygnu

where heads milled .004 ,or .040 ?.004 would be normal for a clean up pass .

A.R. Shale Targa

iTrader: (2)

IVC @ .050" is half the intake lobe...222/2+111 added to the ICL of 110 eq=
221 then minus 180 for a total of 41 degrees ABDC...pretty early...trapping
lots of cylinder pressure. This makes for a smooth idle, good street torque,
and usually decent mileage (gear and converter dependant)