1fastxz

iTrader: (16)

well got my short block together looks like ill have a compression ratio of
12.17:1

short block is a LSX block
bore 4.185 piston is out the hole .007 -2.8 dome valve reliefs
stroke 4.125
rods 6.125
head gasket is .051
heads 70.4cc chambers(LS3 heads)

going to run 93 most of the time but run some 104 at the track

should have some numbers real soon looking to get in on a engine dyno next week or so....

Brian Tooley Racing

iTrader: (13)

My 427 was 11.5:1 and had some knock.

On my 454 I spent a lot of time putting a radius around the perimeter of the valve reliefs by hand and did some other anti-detonation tricks to the chambers and at 12:1 I have no knock.

Keep us posted on your results!

Bobsmyuncle

iTrader: (32)

this guy dont know anything :rollseyes:

haha of course im joking, hope everything is well down in ky brian.


I'm at almost the same exact compression as the OP. ive got alot of timing(30*) and no knock, there are quite a few ways to do it, but obviously require the motor to be apart. i went around my valves reliefs like brian said, and tht seams to help alot. as well as alot of work on the chambers.

OP: whats the quench like on the motor?
What head gaskets?
whats the deck clearance?
What pistons are in it?

1fastxz

iTrader: (16)

Had a lot of the work done to the chambers buy my head guy
the pistons looked good out the box no sharp edges on them
so ill see how it turns out

the comp sould work well with the baby cam im running

03supercobra

iTrader: (38)

I run a shade under 12:1 in my 443, valve relief area has also been softened up a bit. No knock at all on 91.

WKMCD

iTrader: (2)

I ran 12:1 in the first iteration of my 403. I could only run 24 degrees of timing without KR on 93 octane. Second iteration, we dropped the CR down to 11.4:1 and were able to add 5 degrees of timing and picked up about 20-25 RWHP IIRC. The L92 heads love timing. My current setup is also 11.4:1.

I learned not to give up spark lead for compression.

Just my $.02

1fastxz

iTrader: (16)

thanks
thats why i just going to run the higher octane when im looking to make power, the air down here is only good for like 2 months.. damn south......
But we can race almost the hold year

but i'll work on the tune and see how much timing i can run on 93 to, its going to be on pump gas 95% of its life

1fastxz

iTrader: (16)

Got my long block together last night. Looking like ill be dropping the motor off that the dyno tomorrow so that he can make some mounts for it.

Hoping to have some numbers by Monday or Tuesday

chrs1313

iTrader: (24)

same thing was done to my flycut 346... running 26* timing with no knock at 11.9:1

litle88

iTrader: (20)

I'll be 12.02? when I get mine together, Ill have to see my valve reliefs.

chrs1313

iTrader: (24)

I would hit them with some sandpaper 400 grit if they are sharp zeke...

Stage7

iTrader: (1)

11.2:1 here... Good luck with your combo and keep us posted on your results.

litle88

iTrader: (20)

gotcha!

PRE-Z06

what's the cam specs?

Oh4GTO

iTrader: (46)

11.7 in LS3 shortblock with AFR heads.

LSxPwrDZ

iTrader: (4)

11.7:1 in my 403 and no knock at all! I run 26* at peak torque and 28.5* above 6800rpm with no issues. Seem's like the more timing I throw at mine the faster it goes down the track with more trap speed.

Another thing to note is choose a good plug! A spark plug with the right heat range will go a long way in helping create power and keep the right amount of timing in the motor to generate that high cylinder pressure needed. Standard TR6's work well but I prefer a heat range 7 plug on anything over 11.5 compression.

Wnts2Go10O

iTrader: (12)

i want to hear more on ur spark plug philosophy..

hymey

We just picked up another 20 rwhp goin up to 12:1 and ended up only running at 21 deg total timing on 95 ron fuel. Previously it was not timing sensitive and would take a lot of lead but with more comp you will get what they call "negative torque" from to much lead. Normally 4 deg away from real knock event is where best power is. 21 is low but less is best car was so much stronger and angrier and we did not have decent fuel in it. I have never seen a LSx motor make power right till detonation its not the right way to tune them. Motors always pull harder and stronger up top with more compression. I started at 24 degrees in this motor and it was a dog. I new it had to much in it from some very slight knock in the logs around pk tq i new if I went 1 more deg I would have heard marbles.

To run more comp, radius valve reliefs, polish chambers, very tight quench. Cold heat range non projected plugs ie 7s, then u can really push the timing and see where the engine falls off, it will sound soft all of a sudden pull timing back 4 degrees watch the tq come back and keep pulling timing 1 deg at a time until power is down again then add enough timing till power is peaking. Turn the KR off then not required

JordonMusser

iTrader: (1)

All these suggestions are good. Make sure you hand finish the VJ on the chamber side, and also choose the right plug.

Coating pistons/chambers helps too (along with a finer polish on the chamber than normal)

1fastxz

iTrader: (16)

Have it up and running in the car just got it home
Not the final tune yet, want to get a 500-700 miles on the motor before i start jumping on it hard

But so far no issues with knock