HEI Mechanical advance question.
Thread Starter
Instructor
Joined: Mar 2013
Posts: 203
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From: Cincinnati OH
HEI Mechanical advance question.
Im trying to limit my mechanical advance to about 17 to 18 degrees. My distributor currently has right at 22 degrees of mechanical advance with a 375 center plate and 41 weights. I have Vortec heads and only need 32 degrees of total timing so Im hopping one of you guys has played around with the center plat and can give me a GM center plate part number that might get me close.
Thanks.
Thanks.
Had a 1976 L-82, 4-sp
Joined: Mar 2011
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From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
Read this Limiting or locking the mechanical advance mechanism about 3/4 of the way down in the following article:
http://www.crankshaftcoalition.com/w...gal.22_advance
I did it this way with the limiting screw and it does work but it takes time to get it right. I now have a programmable dist'r which gets better results in minutes. Well worth the investment for creating timing curves.
http://www.crankshaftcoalition.com/w...gal.22_advance
I did it this way with the limiting screw and it does work but it takes time to get it right. I now have a programmable dist'r which gets better results in minutes. Well worth the investment for creating timing curves.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
Unless you are racing this thing 2 or 3 days a week, I wouldn't bother with the center plate. What you do need however is a certain colored limit bushing under that plate.
Here are some color codes for MSD bushings that might help on the maximum advance. Some I couldn't find info on.
Red: 28*
Silver: 25*
Green: ?
Blue: 21*
Purple: ?
Black: 18*
Here are some color codes for MSD bushings that might help on the maximum advance. Some I couldn't find info on.
Red: 28*
Silver: 25*
Green: ?
Blue: 21*
Purple: ?
Black: 18*
Thread Starter
Instructor
Joined: Mar 2013
Posts: 203
Likes: 24
From: Cincinnati OH
Thanks for the reply's. From what I've seen the MSD bushing are only for a MSD distributor. If they would work on the stock gm unit that would be an option. Still hopping someone will see this that has played with the center plate. My distributor is in like new shape and I can have the center plate off and a new one on in less than 10 minutes. As far as the screw as a limiting stop if I cant get any info on the center plate that is the direction I may go.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
You are correct and there are two sets of MSD bushings. One for StreetFire and one for the Billet unit. If they also fit other dizzys I am not aware, but maybe.
I have a hunch you will have to do some welding on the slot then open the slot back up to the desired size you need for max adv. That is the whole idea of that black bushing of 18*, you want 17. But, it may not fit your post. So back to the center plate idea.
Edit: Check out Moroso 72300 kit. Claims it prevents over centering issues with center plate. $14 on EBay.
I have a hunch you will have to do some welding on the slot then open the slot back up to the desired size you need for max adv. That is the whole idea of that black bushing of 18*, you want 17. But, it may not fit your post. So back to the center plate idea.
Edit: Check out Moroso 72300 kit. Claims it prevents over centering issues with center plate. $14 on EBay.
Last edited by HeadsU.P.; Apr 18, 2018 at 08:53 PM.
Thread Starter
Instructor
Joined: Mar 2013
Posts: 203
Likes: 24
From: Cincinnati OH
That turned out nice..Easy to see how the MSD bushings would work once its all apart. Still yet there has to be an 74 Cadillac or something that has a center plate/weight combo with only about 16/18 * of advance.
