Hi everyone,,

I got a low mileage LQ4 short block pulled out off a 2006 Yukon Denali and installed on a Lumina SS (has the same look and chassis as 2005 GTO but with 4 doors). Stock LQ4 engine have 9.4:1 SCR with the following specs:

Stock 317 heads 71.06cc
Stock MLS gasket 0.052
Dished pistons -6.45
Pistons are ~ 0.004 - 0.010 out of the hole (-) value for piston to deck clearance.

So, to pump up my static compression, I replaced the 317 heads and intake with a 799/243 LS2 heads, 90 intake, and a 90 FAST TB. With the 243 heads having smaller chamber 64.4cc compared to the stock 317's 71.06cc chamber, the compression was pumped up to ~ 10.2:1

To reach higher compression, I replaced the stock gasket with a 0.041 gasket which increased the static compression to ~ 10.5:1
However, my quench become on the tight side ~ 0.030 - 0.038 depending on the piston/deck clearance exact value.

My questions is:

The stock LQ9 cam specs are 196/207 duration @ .050 and 0.467/0.479 lift on a 116 LSA and with my current 10.5:1 SCR, it puts my DCR at ~ 8.71:1 (stock is ~ 7.84) which is bit high for resisting detonation in our country's hot weather (100 F - 120 F in summer).

So, What would be a good cam for my setup that will give me good PTV clearance and reduce my DCR to the 8.0 - 8.4:1 range?

I have seen great results for LQ4 engines with stock MLS gasket and 243 heads and cams with these specs on LSL or EPS lobes:

226/234 .63x/.63x on 110 LSA
227/235 .60x/60x on 112 LSA
230/234 .595/595 on 113 LSA

I'm thinking of getting one of those grinds but I don't know if my PTV clearance will allow me?

I know, MEASURE IT..... I will, but for now, I need your opinions and your experience with similar setups and maybe some rwhp numbers

It would be great if I can run TSP's 233/239 cam or even a MS3 cam without having to flycut my pistons

If I have to flycut the pistons anyway to get a decent sized cam, I will get LS2 bottom end (from the same guy as he's rebuilding his stroked engine) and flycut the flat pistons to replace my LQ4 stock bottom end and pump my compression ratio to ~ 11:1

In that case, more cam options are available

The car is a 6MT and it's putting down 367rwhp and 402rwtq with the current setup (tiny cam) through a 3.73 rear ratio and heavy 18" wheels

 

This may not help you out at all, but I'll throw it out there for you.

I have an LQ4 shortblock with PRC stage 2.5 LS6 (799) heads on it. Heads were milled .020, and compression using a stock MLS head gasket is 10.55:1. I had Pat G spec me a cam that was ground through EPS, with the condition of no flycutting. I ended up with a .238/.242, .604/.605 on a 112+4. Runs like a champ, and cleared no problem. Hopefully this helps you (for reference on what will clear, anyways).

 

You can't beat $25 for a custom spec'd cam for your specific application. I did the same as Q. Still waiting to start my build but the cam is on the way. PatrickG knows his stuff. I would contact him.

 

I know that Patrick G is the man when it comes to cams and he has been very helpful.

I just wanted to see what other guys are running with similar setup.

 

I know that Patrick G is the man when it comes to cams and he has been very helpful.

I just wanted to see what other guys are running with similar setup.

 

i am running almost the same setup you have i have a 06 lq4 bottom end gm mls head gaskets with 243 heads that have been milled .015 and i am using a tsp 233/239 and have no issues

 

Thank you -Q- and dodson55 for your helpful inputs.

Do you have any dyno numbers for your setups?

 

No dyno numbers yet or track times took it to the track once but the 10 bolt took a dump on the line lol I hope to have some numbers soon but I love my set up below 3 grand it is slow but when u hit the 3k mark its like flipping a switch and it comes to life and pulls hard it drives real good on the street after it was tuned I drive it everyday about 250 miles a week and it gets about 16 mpg if you keep your foot out of it in town and about 24 on the highway

 

I don't have any dyno numbers yet either. Still in the process of getting the street tune completed.