The Ford Barn - Full advance from 28/29

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Full advance from 28/29

I'm having a problem with getting my distributor to full advance as described in Marcos' 1999 paper.
Specifically, I'm not getting the full range. The paper states the arm should swing the full distance of the slot in the distributor body. At full retard the arm just barely touches the body. And with the advance lever full advance, there is 1/4 inch still to travel in the body slot. Net result, I don't think I'm getting the benefit of full spark advance. I have a 28/29 column, but it's mounted to Randy's F100 box. My thought is rotating the column will only move the area of the slot traveled. It won't increase the travel distance. Am I missing something?

Re: Full advance from 28/29

It's a geometry problem, either one or the other ends is out of position or you don't have enough throw on one or the other arm. From the description it sounds more like you need to lengthen the lever on the column so it has a greater ratio (moves the dizzy arm more per degree of movement and adjust it so the full retard position is the same.

Re: Full advance from 28/29

Mine did the same thing. I checked it with a timing light and I was actually getting a lot more advance than I thought, too much. Until you check it with a timing light you don’t know how much advance or retard you are getting.

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Re: Full advance from 28/29

Is the slot in the distributor the correct size? I seem to recall a Ford Service Bulletin that said some had been modified by owners or mechanics to have a larger opening. Though I would think that would require other changes too.

Re: Full advance from 28/29

I have the same issue, but I have kind of discounted whether it is important or not, for the simple reason that on my 29, when I am a couple clicks from the bottom of the quadrant, I think that is about all the advance my engine will handle. In other words, at that level of advance, I don't get any more benefit by going all the way down any way, so what difference would it make if I had even more range beyond that? As far as the cause, I think its due to my after-market upper plate. I have one of the newer style plates for the more "modern" point sets. I was comparing that plate, and more specifically, the length of the advance arm that connects to the advance linkage. It appears that the newer after-market plate advance arm is just a wee bit shorter than the original. That would take some of the travel away from the top to bottom range of the advance. I haven't measured anything so this is just a casual observation and nothing factual.

Re: Full advance from 28/29

If the lever on the column is bent over closer to the column the movement of the rod will be less

Re: Full advance from 28/29

Sideline is right. Check your advance/retard with a timing light. Just because the lever is not moving thefull quadrant does not mean you are not getting the full 28 degrees of advance. Remember, advance is only 28 degrees.

Re: Full advance from 28/29

And - Check out Vince Falter's page on Distributor Advance.

The Model A has more capability for advance than is actually necessary for optimal operation.

Mostly Model B discussion but check out http://www.fordgarage.com/pages/bdistributoradvance.htm

Quote:

The Model A ignition uses a zero crankshaft degree (TDC) initial timing point so that the engine can be easily started by hand crank, however it should never be run under load in this "retarded" position. The advance lever should always be advanced 1/3 to 1/2 travel (13 to 20 crankshaft degrees BTDC) on the steering column quadrant after starting the engine, and should generally not be run more than 3/4 advanced on the column under any normal circumstances. (Bolding mine)

That said with high compression heads much in demand one might not want to stretch the upper limit per the same article and with valid reason.

Quote:

The Model B is a higher compression (cylinder pressure) engine which uses more initial spark advance, and lower maximum advance compared to a Model A. This is consistent with the operation of the B engine and the need to protect it from the effects of running too far retarded or over-advanced.

More discussion of Model A versus Model B timing below including reference to a video.

http://www.fordgarage.com/pages/timingiseverything.htm

Vince is among the most cogent of sources.

Joe K

Re: Full advance from 28/29

I'm guessing you have a standard compression head. If you have one of the higher comp. ratios you definitely don't need the full range of spark advance the lever will give you.

There have been previous threads about incorrect length spark rods. This may be your problem.

Re: Full advance from 28/29

I agree with ryanheacox.

Re: Full advance from 28/29

Quote:

Originally Posted by ryanheacox (Post 1801123)

How does that answer my question? If my spark rod were longer, I would not be able to go full retard in the cap. I can use the full quadrant at the steering wheel. If my rod were shorter it would Give the same span, but less retard and more advance.

I do have a stock head installed, all distributor components are original Ford. The only aftermarket part is the spark rod. It makes no sense to me. I guess I'll go with the answer that I'm getting full retard, and enough advance. I'd still like to have it explained to me.