Distributor upper plate

[Brianfrench65]

I am trying to find a combination of a standard upper plate, (Model A points) that has a center hole, that fits the distributor, without a lot of slip. The closest I can find is about 0.015 diameter difference. I have several distributors and 6 upper plates, and there is too much clearance.

Should I turn the boss on the distributor and press on a bushing?

Am I over thinking this?

[Bruce Lancaster]

One of Marco's distributor rebuilding posts has an illustrated guide to shrinking the hole slightly...basically a bunch of light center-punchings slightly outside the hole all the way around.

[Bob C]

Here's Marco's picture.

Bob

[Bruce Lancaster]

A typical Marco! Eyeball calibrated to .0001 for perfectly spaced punchmarks, beautifully clear illustration.

[MikeK]

Originally Posted by Brianfrench65

. . .Should I turn the boss on the distributor and press on a bushing? Am I over thinking this?

I don't think you're overthinking it at all. It is not just the plate holes that wear. The cast iron dizzy bodies wear smaller and off-center because the cam follower applies pressure in one general direction. The plate hole wears off-center in the opposite direction. You can peen a plate to tighten the hole but if it follows a casting that has worn several thousanths off center the point gap (and thus the dwell) will vary as the advance lever is moved. You might want to take a mic or caliper and check the hub for concentricity.

[Brianfrench65]

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So....my plan is to indicate the bore of the distributor and turn the boss, and make a bushing to match the hole of the upper plate.

Where do I get a GOOD QUALITY upper plate?