Minor Follow up: Point New and Old

[Kevin in NJ]

My brother (Kurt in NJ) has a dist machine. So we wanted to double check what we knew about points. We also hope to fix some bad information. At a later point in time we may create a fact based article on the points and get it published.

There was a comment made about the original points maybe having a weak spring and having float. We know this to not be true. So real quick we pulled a couple of dist out of the box (we have a pile of them) and my brother ran them on his dist machine.

The dist mach allows you to see when the points start to float. That is they do not have enough time to contact and the dwell time gets reduced. That means no spark. You can also see the difference in timing if things are moving. A problem with the A can be the top plate physically moving about altering the position relative to the cam and chaning the gap.

Now this was not a careful and well thought out test. This was just a quick 'lets see what happens' test. My brother sent me the picts, which not very good, and gave me an overview on the phone and I wrote out some notes. Hopefully he will check this out overnight and make sure I did not mess it up.

The right most dist has 1970's Rick's plate and same era points. The points started to float around 8000 engine RPM (yes twice the top end for the average A). As he moved the plate the dwell changed by 15 degrees. That is the upper plate had a bunch of float allowing the points to move relative to the cam.

The middle picture has a set of Wizard points on an era replacement upper plate. The float started at around 8000 engine RPM. Moving the plate caused about 10 degrees of dwell change.

Worn original points on a worn original upper plate got up closer to 9/10,000 engine RPM before float started. When the plate was moved it only had about 5 degrees of dwell change.

It should also be noted the used original Ford A type cam (not the replacement B profile) was dead on 90 degrees and exact in dwell time.

The right most picture is a 67 289 dist run up to about 7000 engine RPM before point float.

I have the assembled dist that will go in my car. When I find it we will see what a NOS point set mounted to a NOS upper plate with like a thou or two of play on the used dist body with a NOS B type cam.

What we do not have are modern repro stuff and a V8 upper plate.
We are looking for donations if anyone wishes to send us a one of the upper plates for the V8 points PM me.

We do not buy any of the new parts for most of this. Often the worn original stuff is better then the repro parts. Over time when opportunity has presented itself we have bought NOS parts because we feel having the best quality parts in some areas is worth the price. Plus, over the years we have read about the troubles people have had with the repro parts. We like to put the car together and not have to worry about it.

Does anyone have the points print? I would like to confirm what it says about the point contact materials.

A side note and the pictures are not a good representation so please do not attempt to make judgements from them. On the black disk on the machine you will see red arrows and a split red thing. This is showing you current to previous place where the points opened (or closed I do not know). The camera shutter speed can not capture this properly if it is jumping around. So what is pictured is not what was actually seen. Well that is if it was jumping around.

Conclusions:
Float does not happen with the original points. Even cheap well used original points.

Good slightly worn original plates may be better then a new repro. I am making this statement because others have found the same conclusion over the decades we have been playing with the A's. It is important to know how much movement you have in the upper plate. You need to understand the center hole of the top plate is the bushing and can be loose because of the dist and or the plate wear. The movement may be more significant then you might like (think odd running issues that are hard to figure out).

[Synchro909]

Very interesting stuff!
I've long suspected that what some people assume to be point floating is in fact, the valves floating at higher revs. The two are easy to confuse as they both impose a limit on the revs. This test seems to confirm it isn't the points limiting the revs.
Let the debate rage!!

[700rpm]

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Nice work, Kevin. And thanks for the summary.