I've got a question about timing advance on a carb'd LQ4...

Engine mods are as follows:

-04 stock LQ4 short block 140k miles
-799 heads milled .005
-Comp XE-R 232/238 .595/.605 110 LSA +4 adv
-Vic Jr. Intake manifold
-ProForm 750 mech carb

Now, I find it interesting that on an old school carb'd 350 you gotta run at least 34+ degrees timing to make any power, but most everyone with a carb'd LS engines are only running about 28* (same as fuel injected). I know that the LS engines are a bit more efficient than the SBC's, but that much? I guess what I'm wondering, is the cam the reason? Most people are running EFI cams with their carb setups. My cam is spec'd specifically for a carb setup, much earlier ICL.. Should I try more timing? I'm at 28* now, I was thinking of trying like 32...

 

Nobody?

 

Where is your compression ratio at with this setup? You could always try a little more timing and see how it acts. Guessing you aren't going to be on a dyno with this?

 

The LSx is much more effecient than the old small black and big block. I ran mine with 30* timing, then tried 32* and didn't pick up much. Backed it back down to 30* and may even try 28*.

 

Its in the heads, the more efficient the heads are, the less timing is needed for max power. SBC rocking 23* heads could crank timing up as high as 38-40* depending on setup and make good power. Most LS setups will like anywhere from mid 20's-30*. Of course there are exceptions. But as Phantom mentioned, the more efficient the engine is, the less timing will be needed for power.

Look at the vvt 6.2 engines, they make great power on much less timing due to the vvt. Full advance down low, spark timing in the high teens to low 20's, retarded cam timing up top and ramp the ignition timing up a bit. My car (l99) runs 23-29* of timing at wot.

 

Unfortunately no, the nearest dyno is 3.5 hrs away... I've got a full exhaust on the truck so I'll be able to hear pinging, I guess I'll just have to try it. The first time out with the truck I was using the Curve 1 pill that came with the 6LS, it had 35*'s! It ran damn good, but I had straight headers, so no chance of hearing any pinging lol.

Phantom, is your cam spec'd for a carb setup? I'm still thinking that would make a difference as to at what timing advance a setup would make the most power... But IDK

 

Ok, yeah that makes sense. Only thing I guess I'm still wondering is if the way I spec'd my cam will make a big difference on what timing or not, my ICL is pretty early at 106*...

 

Don't have my DCR calculator tool right in front of me at this moment but just doing some quick figures in my head it looks like your DCR dynamic compression ratio should be right around 8.1:1 which is healthy but not really high. The DCR plays a role in how much timing a motor will be able to "take" without detonation. But of course more timing definitely doesn't exactly mean more power in many cases, I've proven this many times. 15 degrees overlap with that cam you've got there, nice!