Mechanical advance in old school C5AF-E distributor

[Rick Parker]

What I should have said was the OEM lengths but lighter gauge..sorry that would be the desired change usually to create a quicker curve. Another way is to carefully increase the weight of each individual weight, by adding solder or brazing a small nut to the weight. Different ways to achieve the same result.

[dcdoug]

Originally Posted by Wbulk

Do you have a vacuum advance distributor or was it modified so the vacuum advance was removed? If it was removed the points mounting plate needs to be secured so it does not rotate/shift. If that rotates the advance changes. Just a thought.

Wayne

Mech advance only. Never had vacuum. The points have been replaced with a Pertronix ignitor, which is on it's own secured replacement plate.

[Wbulk]

OK, then check where the upper shaft and the lower connect together. It has to return to the stop by spring pressure. Take the points plate off. Spin it and play with it until you see when it will not return to the stop. Then see where it is hanging up.

Wayne

[dcdoug]

Originally Posted by Wbulk

OK, then check where the upper shaft and the lower connect together. It has to return to the stop by spring pressure. Take the points plate off. Spin it and play with it until you see when it will not return to the stop. Then see where it is hanging up.

Wayne

I will look at it again. The thing is that it does return easily by hand right now, but I guess there must be someplace that its hanging up at least a little bit.

[dcdoug]

Does it matter which side the heavier spring goes on or is it all the same and having the right combo of light/heavier springs is what's important. I should have the springs tomorrow. My current plan is to keep one of the current very light Mr. Gasket springs and add one of the lighter springs in the MSD kit that seems to fit best for length.

[patrickt]

I don't know the answer on your distributor (the answer on my MSD distributor is that it doesn't matter). FWIW, here is the curve on my setup. We're more similar than different, although you have iron heads. I think you would be happy with an advance that looked similar to what I'm doing.

[dcdoug]

It doesn't look like it should matter to me, but maybe Wayne will confirm that.

I am thinking the blue spring (size should be right for that one for sure) plus keeping one of the light Mr. Gasket springs, but I'll compare tension when I get them.

I think that advance curve would work quite nicely for me. I'd like to be all in between 2,600-2,800 if possible.

[Wbulk]

No, it does not matter if the slop is out of the springs. Meaning tension is on them at rest. Some of those distributors had tangs that you bent in or out to set where the curve started and or slowed. So with stock springs it mattered for at what rpm it hit the second spring. But for after market it's all about spring tension.

Wayne

Update on Springs
I just read an article on after market advance springs. They had tested all after market kits on a distributor machine. While the article was about GM points distributors it recomended never using the lightest springs. It said they lose their tension to fast and will not return the advance to zero. For what it's worth.

[dcdoug]

Now that is interesting. I bet that's what happened. Probably right at the limit of having enough tension, but maybe not all the time. Maybe I'll replace them both with the two lightest MSD springs (silver and blue) that everyone else seems to run and hopefully that works out. I'll report back. Thanks Wayne - super helpful.

[dcdoug]

So last night I replaced both super light Mr. Gasket springs with the lightest MSD springs (silver), both of which are heavier than the ones I had in there. Hopefully that will do the trick. I couldn't test it because it's been pouring rain. Hopefully tomorrow AM I can test it before heading out to the CACC cruise weekend. If not, I am bringing the rest of the MSD springs and can go up to a silver and a blue spring.

[dcdoug]

Update - the two light (silver) springs from MSD seem to have done the trick. The advance now comes back fairly quickly to zero advance when you release the throttle. I am still at 16 degrees base and 36 degrees advance, all in by 3,000-3,100 RPM (not easy to get it exact doing it yourself and trying to modulate the throttle linkage, watch the timing, and watch the tach at once). I'll confirm with a friend soon, but seems to be good.

I wouldn't mind the advance coming in a little earlier, but I am worried that if I go back to one of the super light Mr. Gasket springs and one of the silver MSD springs that I will quickly loose some of the tension in those springs and run into the same problem of my advance not retarding when the RPMs drop. I'll probably leave it for now as it seems to run well.

[patrickt]

More importantly, when you reinstalled your distributor did you take care to have the #1 plug terminal in the same stock position just like it came from the factory? Jerry will give you points off for that if you didn't, you know....

[dcdoug]

I marked the rotor/distributor and it all went back in exactly as it came out. I also put on a new cap, which has the #1 plug terminal marked and that was lined up correctly too.

[patrickt]

Originally Posted by dcdoug

I marked the rotor/distributor and it all went back in exactly as it came out. I also put on a new cap, which has the #1 plug terminal marked and that was lined up correctly too.

Dang.



...

[10w30dna]

Just thought I would add my 2 cents about distributor advance calibrating..The absolute best way is to find an old-timer ( like myself ) that specializes in distributor servicing. There are probably hunderds of combinations of springs that will produce hundreds of different advance rates. Unless you have the equipment it is a long,painfull experience to get it right. Some people love to tinker and others like to get it right and move on. If I can help out please check my website Tim O'Connor Distributor Rebuilding and Restoration - Home for more info. Have fun with those cars!!!!!!!!!!!