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Old 07-05-2008, 03:55 PM
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Limiting Mechanical Advance

Does anyone know of a kit that will allow one to limit or vary the total mechanical advance on a GM hei?? I would like to limit it to about 18* total.

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Old 07-05-2008, 05:00 PM
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Sure, there are a lot of kits available. Check out your local speed shop or Summit/Jegs. There's an allen key that comes with the kit that you stick in the vaccum and turn the screw in or out to vary diaphram stop, also three sets of springs too.
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Old 07-05-2008, 05:28 PM
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Moroso make the only one that is correctly engineered to not over advance like most others(Accel, Mr.Gasket). It's the only one I'd recommend.
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Old 07-05-2008, 05:38 PM
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http://store.summitracing.com/partde...0&autoview=sku

http://static.summitracing.com/globa.../mor-72300.pdf
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Old 07-05-2008, 06:02 PM
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Pertronix has a kit with little straps of different lengths designed to hang on the spring pegs and limit how far the weights can travel. Its a little hokey, but it works quite well. There are also bushing kits that limit the weights.

Or, you could go grassroots like I did. I brazed some #10 allthread to the bottom of the baseplate. I can thread a nylock nut on it to adjust where I limit the weights
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Old 07-05-2008, 07:49 PM
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Some of you didnt understand. I'm not talking about the vac advance. I'm talking about the weights and stop plate.

I have looked at jegs and summit, problem being is the MSD kit only fits MSD distributors, etc.

The Moroso kit only slows the advance and does not limit it, so, it is still climbing at 4500 rpm. This isnt acceptable. I want to limit the max advance to 18* @ 2800 rpm, and use 18* initial. In the old days we used to drill holes and use roll pins which worked very well. But, I was hoping by now that someone would have made a kit. I still have found anything.
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Old 07-05-2008, 08:16 PM
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Kits for GM distributors used to include weights and springs.
The angle of the weight arms that contact the shaft cam are ground to different angles to limit the maximum advance. Some used to be ground to actually begin reducing the timing as rpm continued to increase.

I haven't looked in years, not sure they still make the things.
All we use are hi-po distributors now-a-days. MSD, DUI, etc.

****

ya, techinspector has the right stuff !!!!

see the arms and center cam, I bet they are ground at differnt angles than stock to limit the total degrees. The sheet says 24. Careful thought and careful grinding can make them into 18* I bet.

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Old 07-05-2008, 09:50 PM
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Pertronix D9001 is a weight/advance kit that includes bushings to limit mechanical advance.
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Old 07-05-2008, 10:14 PM
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The pertronics D9001 is for 24* and non adjustable. The moroso is also 24* and the weights are so light that even with the lightest springs it takes 3500 rpm to get 18*. What I may have to do is use my stock weights, heat them at the narrowest point and bend them in. I already have the proper rate. i just want to stop it at 18 instead of 24*. A blip of weld on the plate would work as well, I guess. Can't believe nobody has made a kit for this after all these years.

On edit:

Here is what I needed. There is a slot that needs to be shortened. I can make a bushing for that or weld a portion of the slot.

Last edited by Greg T; 07-05-2008 at 10:39 PM.
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Old 07-05-2008, 11:23 PM
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Quote:
Originally Posted by Greg T
Can't believe nobody has made a kit for this after all these years.
Yeah Really...

The bushing idea is a good one. JUST intalled a billet HEI from MSD for a friend. VERY nice piece. (if you wanna pay the bucks)

I did, he did. Two happy customers.

MSD provides 4 bushings. The stud you circled is longer and threaded 6-32 and has stainless non magnetic hardware (nice touch) to fasten the different bushings you want to use. Looks like you found a pic of a points style shaft.

For his engine we ended up with:

20 initial +
25 mechanical

45 all in at around 3000. Two blue springs. Vacuum advance adds another 15 at cruise above idle. Rev limit set at 6500. Yes they even have a built in rev limiter...
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Old 07-06-2008, 06:11 AM
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Yeah, grabbed the first pic I could find. I'll have to steal an HEI from my kid to do some R&D with. The HWI must be similar in design.
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