Engine and Transmission Tech

This is another one of those posts where I confess that I'm not really that much of a motor-head...

I had no idea that the springs in my Mallory Unilite distributor would lose so much snap just due to time!

According to Mallory, the Unilite distributor (part number 4764301) on my Buick 215 was factory calibrated to provide 24 degrees of mechanical ignition advance. I installed it sometime around 1995.

Being poor and ignorant for much of the last 13 years - and not owning a timing light with a "dial-back" feature - I took for granted that the advance curve would remained unchanged... but this week I finally invested in a Craftsman dial-back timing light. I learned that I'm only getting about 10 or 11 degrees of mechanical advance! What!?! How could that be?

One of the reasons that I didn't notice this problem is that I've had an old-school habit of just setting timing by "ear". Apparently I don't have a very good ear. It seems I compensated for the lack of mechanical advance by boosting initial advance way up. (Incidentally, I'm getting about 14 degrees of vacuum advance at 15" of Hg - that part is fine.)

So, I called our friendly neighborhood distributor specialist: Jeff Schlemmer at Advanced Distributors.

Jeff explained that Mallory uses very, very light gauge advance springs. How light? Something in the neighborhood of twenty times less spring tension than my old Delco-Remy/Buick distributor. The light gauge springs in the Mallory go soft due to age whether you run the engine or not!!!

I've decided to dig out my spare 1963 Buick distributor and to send it to Jeff for a re-curve and for installation of a Pertronix Ignitor module. (Re-curving the Unilite is easier and cheaper, but won't last as long. Besides, I'm pissed at Mallory.)

I'm looking forward to better throttle response, more torque in most driving conditions, and probably better fuel economy too.

So... have you guys seen similar problems with Mallory distributors?

Have you rechecked your ignition advance lately?

Maybe it's time to invest in one of those new-fangled timing lights?

Very interesting. I recently rebuilt the original distributor on my 215 (have not yet fired it up though pending finding a radiator) and used the lightest springs that came in the rebuild kit. Obviously that is 70's think, heaviest weights and lightest springs. Perhaps I should rethink that.

Well I have a Unilite on my 8 and haven't checked it, but I will say that after dealing with Jeff personally, I'd tend to believe what he said.

Without wishing to sound too much like a cheerleader, it's rare these days to find someone who 1) knows what he's talking about and 2) stands by what he does as much as he does.

I've yet to find ~anyone~ with a negative experience dealing with him. I don't know ANY other TR supplier that I can say that for.

Had the pleasure of meeting Jeff at this year's V8 Meet in Wisconsin. Very sharp guy. Would love to have him do a seminar using tailpipe wideband O2 tuning at the next V8 Meet.

That'd be a real good idea Carl, I second the motion.

Wouldn't weak springs cause the advance to come in earlier? Plus isn't there a variety of different tension springs available? It would seem that at some point they would stop getting weaker (unless they eventually uncoil altogether, who knows?) As far as total mechanical advance, do you still have the red plastic stepped calibration tool that's used to set the mechanical limit? Was it ever set or checked before initial install? Just a few questions that come to mind.

Jim

I build custom distributors for old Datsuns, have the same problem. Seems the lighter spring is so weak that the advance start below idle speed, so at ~800 rpm idle, you are already halfway through the curve. Total advance stays the same, you are just using the second half of the curve
No surprise with 40 year old springs. More initial spring tension helps, but they still advance a bit too quickly, as the spring rate is lower.

Dave
East Coast Roadster

Carl, that will make Jeff a pretty busy guy as far as tech sessions go, I though the two of you were going to give us a tech session on installing a fly off hand brake and then doing boot leg turns! LOL

Sure. Can I flat spot your tires, Bill?

Guess I better get with it & get my part ordered from Jeff.



Edited 1 time(s). Last edit at 03/05/2009 04:17PM by MGBV8.

So how do you fix it? New springs, heavier springs?