A little background. I was fiddling around with the distributor for my 223. I was trying to install it but every time I set it into the engine, I noticed that the rotor was pointing between the posts in the cap when I had it timed! That's no good.

I ended up pulling that little points cam off the top of the distributor shaft and resetting it so that the points open when the rotor is pointing right at the post. Everything looks good now.

But it got me thinking all about the relationship between the camshaft (and the crankshaft by way of the timing chain), the distributor rotor and the points (or the reluctor).

So here's the punch line: if you try to correct the retarded camshaft in the 400 by advancing it with a new timing chain, won't that throw off the distributor rotor. I suspect you'll have to do what I did and reset either the points cam (or the reluctor in the case of electronic ignition). If you don't you'll be causing;
cross firing to the wrong post
increased ozone caused by the spark having to jump through so much air (ozone will eat up the metal under the cap)
loss of spark energy due to the increased air resistance
retarded spark timing because the secondary current will have to build up on the rotor before it gets enough voltage to overcome the increased resistance caused by the longer distance to the post.

The symptom will be a misfiring at high vacuum because the combination of the advanced rotor, and the vacuum advance will turn the rotor too far from the correct post. This would be especially bad on vehicles tuned for EGR because of the extra advance used to compensate for the effects of EGR.

After my experience with the 223, I'll be checking every engine I assemble to make sure that the distributor is 'phased' right; the rotor is pointing to the post when the points open.

 

There is something wrong with your conclusion of why the spark wasn't timed to when the rotor is aligned with a post inside of the distributor cap. The camshaft timing has no effect on how good or bad the rotor alignment is when the spark occurs. You know that the spark is controlled by the points cam or reluctor as you stated. You should also know they (points cam or reluctor) alone are not affected by the advancing of the cam. The rotor, points cam and or the reluctor would have to slip on the shaft somehow for the problem as bad as you described to occur. How can the rotor alignment notch in the top of the distributor shaft, the points cam or the reluctor move from their fixed positions because of changing the cam timing since they move simultaneously with the distributor shaft? Your distributor must have been assembled improperly or somehow the points cam or reluctor has slipped from their original positions. Obviously it can occur since yours was off so far.

No matter what anyone does (short of disabling the spark advance system) to get the rotor dead center of the posts in the distributor cap when the spark occurs they will fail. This is simply because of the vacuum advance and mostly the centrifugal advance inside of the distributor. Imagine how far off center the rotor will be with a 30 degree or more total advance while driving around in your vehicle.

Did you happen to notice how wide the tip of the rotor is? Ford knew what I described about the amount of rotor and cap post misalignment when they built those old ignitions.

One last question. How did you see the misalignment of when the spark actually occured?

 

Actually the rotor should be pointing "behind" the post when at rest and the points open so the mechanical advance can move it into alignment and then a little ahead of the post as the mechanical advance mechanism works.

Distributor caps were enlarged when higher firing voltages were introduced in order to prevent crossfire.

Paul I think you are thinking too much, go get some milk and cookies and go to bed

 

Paul,
Don’t go to bed yet…. You are on the mark.. This is called rotor phasing; probably one of the best kept tuning secrets.
The easiest way to check this without a high dollar distributor machine is to simply get another cap, cut a hole in it so you can shine a timing light in and see the rotor and a post while it is running. Rev it up and watch !!!

 

"So here's the punch line: if you try to correct the retarded camshaft in the 400 by advancing it with a new timing chain, won't that throw off the distributor rotor. "

It's as simple as retiming the distributor.

 

When you cut that hole you should see the rotor move just like I described above as rpm's increase. On points ignitions a test light can show you when the points open and a careful manipulation of the mech advance mechanism will show you where the rotor points. Electronic ignitions are a little trickier. The window in the cap would be the easiest method there.

 

Scroob,
I allready answered the question and the answer is no. The camshaft timing being changed cannot effect the rotor alignment in relation to the distributor cap post when the spark is distributed.

I know of no way to get the rotor and post aligned better than Ford designed it without slotting the mounting holes in the points plate and aligning it myself or have and adjustable vacuum advance arm that allows you to set this "rotor phasing". If I were in the business of inventing and improving ignition parts I would create a rotor that is adjustable on its axis. There, now the problem is solved if a company will just make them.

 

some MSD dizzies have a "phase" adjustment. prolly only the GM HEI's?

 

Purely Ford, I think I see my mistake, the relationship between the rotor and the reluctor doesn't change although they get advanced when the cam gets advanced. Advance the distributor body and everything's back in phase.

I might have caused my problem myself; I had to replace some part of the distributor and that may have caused the out-of-phase of the points and the points cam.

And, Eric, you're right about the rotor being at the leading edge. I took it apart about five times trying to get the rotor positioned just right. When I finished, the leading edge of the rotor was at the front edge of the post. I tested it by rotating the points plate to see if the vacuum advance would pull it too far across. I got it just right.

And, yes, PF, I realized that the width of the rotor together with the width of the terminal post should be equivalent to the total advance of the distributor's advance in degrees. I might actually measure the width of the cap to do the calculation and conversion to degrees to double check this, but I could tell by rotating the points plate that the vacuum advance rotated the rotor just about the exact amount of its width. I do have extra caps so I will be cutting the top off of one to see that relationship and to measure the size of the gap between the rotor and the posts.

 

"Scroob,
I allready answered the question and the answer is no. The camshaft timing being changed cannot effect the rotor alignment in relation to the distributor cap post when the spark is distributed. "

If you advance the cam timing, you also advance the distributor timing. The distributor runs off the cam - anything you do to the cam also affects the distributor.

In other words, moving the cam forward in relation to the crank also moves the distributor rotor forward in relation to the cap. However, this may not be the optimum ignition timing.

 

Ummm, yup, after a cam install you have to reset the ignition timing. Kind of hard to not have to reset the timing when you pull the dizzy. Not that I haven't got a dizzy back in and made some "adjustments" with my tongue in the corner of my mouth and when I set the timing light on I was within a degree or so

Some call it pure dee luck and so do I !

 

Wasn't the original post about rotor alignment to the cap post and not ignition timing?

I got the impression that pcmenton already understood how to adjust the timing when done with his cam advance. Wasn't the rotor being off the main issue here?

I never said that the distributor wouldn't have to be reset to maintain the original timing after advancing the cam. I am sorry if what I said implied this. Explaining the rotor phasing was all I was doing.

Anyway, I think someone should make an adjustable rotor for our Fords to help with this rotor phasing problem.

 

PF, I never answered your question;

One last question. How did you see the misalignment of when the spark actually occured?

With that old 223 distributor (it uses points) I turned the distributor until the points started to open. Unfortunately, they were opening when the rotor was between posts. No matter how I put that distributor in there, it wouldn't line up right with the posts.

I took it apart and moved the points cam around until I thought I had it right. Actually getting it right took about five tries. Every time I pressed that little cam on it would rotate slightly and I'd be off by just a hair. It took hours but I got it about right.

I'm looking forward to firing this engine up. I took so much care with getting everything fixed, it should run pretty nicely. I'll be buying some wire core plug wires on my next trip to NAPA just because that's what the original engine had.

 

pcmenton, your eyes are way better than mine! I am going to look at my old fords ignitions and see what I find since you have had the rotor phasing problem. Being that my eyes are not what they used to be I'll have to use a meter to test the continuity of the points to tell when they open.

Let us know how it runs when you get it all done.

 

I still have an old test light with clips on the ends of long wires to use for static timing old point systems. It seems I don't throw anything away.