71 LT1 ignition timing
Race Director
Joined: Mar 2017
Posts: 11,930
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From: Virginia
Stock springs will keep advancing well past 3000 RPM. To get full and final advance at 2800-3000 RPM, I had to use one light and one medium Mr. Gasket spring. Do the weights have an advance limit stop?
Old Pro Solo Guy
Joined: Dec 2017
Posts: 8,037
Likes: 4,390
From: Marlton NJ
Before you set the timing to 36 degrees at 3000, you absolutely must confirm the timing stops advancing there.
The stock distributor setup will only be part way advanced at 3000 and will actually continue to advance to near 5000.
The 36 (with vac disconnected) is a max number. You should never go past it.
Ask Lars for his timing papers and follow them exactly.
If it is still advancing at 3000, you need new springs.
Do not drive it hard like that or you may hurt the engine with over 36 degree advance.
The stock distributor setup will only be part way advanced at 3000 and will actually continue to advance to near 5000.
The 36 (with vac disconnected) is a max number. You should never go past it.
Ask Lars for his timing papers and follow them exactly.
If it is still advancing at 3000, you need new springs.
Do not drive it hard like that or you may hurt the engine with over 36 degree advance.
Race Director
Joined: May 2006
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Typically a Mr. Gasket 928G kit is used for lighter springs plus the nylon factory advance stop is usually either damaged or completely gone and is replaced with the metal bushing in the kit.
Thread Starter
Advanced
Joined: Oct 2022
Posts: 56
Likes: 6
From: Orland Park Illinois
Stock springs will keep advancing well past 3000 RPM. To get full and final advance at 2800-3000 RPM, I had to use one light and one medium Mr. Gasket spring. Do the weights have an advance limit stop?
Tech Contributor
Joined: Aug 1999
Posts: 14,375
Likes: 6,375
From: At my Bar drinking and wrenching in Lafayette Colorado
I just sent you the timing papers, so you have the info you need now. As a quick way to set it up and check it, use the technique outlined in the paper of simply removing one of your stock springs and then rev'ing the engine up to see where the total advance is "pegged out." Set that point to 36. Re-install the spring that was removed and see if it allows that 36 total to then come in around 2800-3000 rpm. If not, you need to play some mix-n-match games with some different springs and tensions. Also, once you re-install the stock spring, check to see what your actual initial timing ends up being. If it's below 10, your advance stop bushing is probably missing, causing your centrifugal curve to be too long. Follow the guidelines in the papers to install the bushing and shortening your advance curve so you end up with initial timing in the low- to mid-teens while maintaining the 36 total. Then, hook up your vacuum advance and limit its stroke to no more than 12 degrees.
Lars
Lars
Thread Starter
Advanced
Joined: Oct 2022
Posts: 56
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From: Orland Park Illinois
Everything worked out perfect. Removed the spring from dist. Set timing to 36 @3000 rpm. Reinstalled and initial timing went to 14 degrees. The full 36 degrees came in at 3000 rpm. Looks like someone played with the springs because one was deformed. Black springs looked like original GM. Maybe one was starched. Thanks everyone for the help. Lars unbelievable thanks for your help and technical data. Some day hope to buy you guys a beer. Not sure why the timing was so far advanced. Maybe the dist was a tooth off or I missed read the timing light. Runs good now. No miss when not load. Starts good. And accelerates good. Heading to Blackhawk motorcycle show/ swap meet tomorrow good show in Davenport Iowa.
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Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Everything worked out perfect. Removed the spring from dist. Set timing to 36 @3000 rpm. Reinstalled and initial timing went to 14 degrees. The full 36 degrees came in at 3000 rpm. Looks like someone played with the springs because one was deformed. Black springs looked like original GM. Maybe one was starched. Thanks everyone for the help. Lars unbelievable thanks for your help and technical data. Some day hope to buy you guys a beer. Not sure why the timing was so far advanced. Maybe the dist was a tooth off or I missed read the timing light. Runs good now. No miss when not load. Starts good. And accelerates good. Heading to Blackhawk motorcycle show/ swap meet tomorrow good show in Davenport Iowa.
9 of 10 vintage cars and bikes I get here are hopelessly out of tune and 5 of those were "tuned" by "experts" who have "been doing this for 30 years"........
Good on you.
Jebby