Timing vs Cam vs Carburetor
03-29-2012, 03:57 PM
#1
Timing vs Cam vs Carburetor
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...
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...
Last edited by LS1FREEK; 03-29-2012 at 09:27 PM.
03-30-2012, 07:34 AM
#3
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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?
03-30-2012, 09:34 AM
#5
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.
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.
03-30-2012, 09:36 AM
#6
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
03-30-2012, 09:42 AM
#7
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.
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.
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03-30-2012, 12:22 PM
#8
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15 degrees overlap with that cam you've got there, nice! 
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