Quick timing question
Thread Starter
Melting Slicks
Joined: Sep 2006
Posts: 2,814
Likes: 469
From: Wichita Kansas
Quick timing question
Most of what I have always read says the (factory) 8° is ridiculous, go with 12°. I think for more power, run better, might be less efficient. So I'm set on that for my L48 '72. (And gives me 30° with vacuum and 700 rpm idle). Won't do any harm? Thanks
Last edited by kansas123; Jun 6, 2025 at 03:36 PM.
Tech Contributor
Joined: Aug 1999
Posts: 14,379
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
You need to check and set your total timing and make sure the total is at 36. Once done, see what your initial ends up being - it should fall somewhere in the 10-16 range. Setting the initial without knowing the resulting total timing is what can do harm...
1967 Pedal Car Champion
Joined: Mar 2020
Posts: 9,135
Likes: 4,245
From: US-PNW
I'd say doing this sort of all-in timing results in a more efficient engine than the retarded timing on the label. You get better combustion at a more optimum place in the cycle and rpm range.
Last edited by barkingrats; Jun 6, 2025 at 09:06 PM.
Instructor
Joined: Apr 2018
Posts: 165
Likes: 92
From: Buxton ME
David - I think you mis-understood Lars' comment, total timing is not initial plus vacuum at idle, it's initial plus mechanical at full advance at some rpm that brings in the full travel of the weights. Search for his papers on getting the distributor and the timing correct, it'll make a world of difference.
Thread Starter
Melting Slicks
Joined: Sep 2006
Posts: 2,814
Likes: 469
From: Wichita Kansas
David - I think you mis-understood Lars' comment, total timing is not initial plus vacuum at idle, it's initial plus mechanical at full advance at some rpm that brings in the full travel of the weights. Search for his papers on getting the distributor and the timing correct, it'll make a world of difference.
Tech Contributor
Joined: Aug 1999
Posts: 14,379
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
David - I think you mis-understood Lars' comment, total timing is not initial plus vacuum at idle, it's initial plus mechanical at full advance at some rpm that brings in the full travel of the weights. Search for his papers on getting the distributor and the timing correct, it'll make a world of difference.
Lars
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Burning Brakes
Joined: Oct 2001
Posts: 925
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From: TX
Kansas
I copied this out of my records for my 1969 350/300 Corvette. This will give you an idea of where the numbers will end up. The advance limiting plate from Lars smoothed out low rpm acceleration, ie, going from 55 mph on say 60 mph.
VS
February 1- Installed Lars’ Vacuum Advance Corrector Plate with new B26 vacuum canister (Napa VC1765) replacing the B1 can at Lars suggestion. Idea is to limit vacuum advance but let it come in at a lower vacuum level. This is done because initial mechanical advance is set to 12* with a total of 34-* all in at 2900 rpm and you want to avoid having total mechanical plus vacuum at over 52*. I set the timing as above, mechanical plus vacuum is about 46* with the new can adding 12*. Idle at 750 rpm.
Test drive was perfect. Smooth strong power, instant response @ 71,626 miles.
I copied this out of my records for my 1969 350/300 Corvette. This will give you an idea of where the numbers will end up. The advance limiting plate from Lars smoothed out low rpm acceleration, ie, going from 55 mph on say 60 mph.
VS
February 1- Installed Lars’ Vacuum Advance Corrector Plate with new B26 vacuum canister (Napa VC1765) replacing the B1 can at Lars suggestion. Idea is to limit vacuum advance but let it come in at a lower vacuum level. This is done because initial mechanical advance is set to 12* with a total of 34-* all in at 2900 rpm and you want to avoid having total mechanical plus vacuum at over 52*. I set the timing as above, mechanical plus vacuum is about 46* with the new can adding 12*. Idle at 750 rpm.
Test drive was perfect. Smooth strong power, instant response @ 71,626 miles.
