Initial (Base) Timing settings on a '70 LT-1
Thread Starter
Instructor
Joined: May 2004
Posts: 247
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From: San Diego / Los Angeles CA
Initial (Base) Timing settings on a '70 LT-1
I am planning on doing my Timing tomorrow and as such was looking for what my initial timing should be set to. I would also like to know where my dwell should be at (28-32?) and what my total Timing should be at (36?).
I have the 1970 Chassis Service Manual and the AIM for 1970 yet I can not find it in either of the books (granted the 70 Chassis Manual is for 69 Vettes).
Thanks in advance,
Mike
I have the 1970 Chassis Service Manual and the AIM for 1970 yet I can not find it in either of the books (granted the 70 Chassis Manual is for 69 Vettes).
Thanks in advance,
Mike
Thread Starter
Instructor
Joined: May 2004
Posts: 247
Likes: 0
From: San Diego / Los Angeles CA
Never mind I just found it. Dwell should be set at 28-32.
Timing for the LT-1 is listed at 14degrees B
New questions:
B = B.T.D.C. = what?
What does each tick equal (2degrees per click?) on the ruler by the belt?
Remaining question:
What should my total timing be at?
thanks again
Timing for the LT-1 is listed at 14degrees B
New questions:
B = B.T.D.C. = what?
What does each tick equal (2degrees per click?) on the ruler by the belt?
Remaining question:
What should my total timing be at?
thanks again
Last edited by magelin; Nov 20, 2009 at 11:15 PM.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
BTDC = before top-dead-center
You are mixing up some issues with your question. You can set timing a number of ways: GM would have you set "initial timing" at idle and ignore where the timing is at elevated RPM's. Essentially, GM wants you to assume that the distributor sets timing properly at every other rpm once you set the initial timing at idle.
Folks who work with engines all the time think a better approach is to establish the proper behavior of 'mechanical' advance throughout the useful rpm range and optimize that for your particular engine based on best performance of the engine. Then appropriate vacuum advance is employed for best operation at idle and while cruising. Once that is done, idle timing is 'what it is'...you don't set it; it's a result of your other work. As long as it is in the range of 8-16 degrees BTDC and the idle is smooth, you don't care what it is.
You can't do both, because they are two entirely different ways of setting timing for the engine. GM's approach is simple, but leaves a lot of performance off the table. That was to GM's advantage, as it reduced warranty costs.
Find and read technical papers on timing written by Lars Grimsrud [in the CF Archives] and follow his process, if you want good engine performance. If you prefer to have a "dog" of an engine, but one that will last longer, use the GM timing method. Either will work...
You are mixing up some issues with your question. You can set timing a number of ways: GM would have you set "initial timing" at idle and ignore where the timing is at elevated RPM's. Essentially, GM wants you to assume that the distributor sets timing properly at every other rpm once you set the initial timing at idle.
Folks who work with engines all the time think a better approach is to establish the proper behavior of 'mechanical' advance throughout the useful rpm range and optimize that for your particular engine based on best performance of the engine. Then appropriate vacuum advance is employed for best operation at idle and while cruising. Once that is done, idle timing is 'what it is'...you don't set it; it's a result of your other work. As long as it is in the range of 8-16 degrees BTDC and the idle is smooth, you don't care what it is.
You can't do both, because they are two entirely different ways of setting timing for the engine. GM's approach is simple, but leaves a lot of performance off the table. That was to GM's advantage, as it reduced warranty costs.
Find and read technical papers on timing written by Lars Grimsrud [in the CF Archives] and follow his process, if you want good engine performance. If you prefer to have a "dog" of an engine, but one that will last longer, use the GM timing method. Either will work...
