uneven point gap as dist is rotated
 

Distributor acts like a uneven cam as I rotate shaft .that is one lobe is 30 thou next lobe 20 thou and so-on...tried two cams both similar checked shaft play seems real tight ? whats going on here ???

Re: uneven point gap as dist is rotated
 

Bushings not reamed in the center.

Received this PM

Hi Mike,
The bushing is fixed so if it were off center, it would not impact the varying gap as the center of the shaft stays at center of reamed bushing.

I have seen the cam machining on new distributor shafts be off (concentric)as much as .004" which translates into .008" when spun 360 degrees. Given some old cams were also off, it is possible the two are adding...but the amount he is observing seems over the top of possibility.

Good Day Mike!

Dave Gerold

Re: uneven point gap as dist is rotated
 

Re: uneven point gap as dist is rotated
 

When this happened to me the shaft was worn out .!! Crap repro part that had only been in there for 500 miles.

Have you removed the distributor ? to check that the shaft is tight in the distributor bushings no sideways play !!

John Cochran

Re: uneven point gap as dist is rotated
 

Couple of years ago we had the same problem with NEW top shaft , seems when they were machined out of round & one point reading was 5-7thou less than the other 3 ,contacted the supplier, they airfreighted another batch from a differant supplier , same thing , their 3rd supplier was able to send yet another batch of which checked out correct ,Mac,s often send me parts to check , So i beleive you have an out of round shaft where the rotor fits , We set them up with a dial guage kit i purchased at a National meet , Hope this helps , Derek from still wet NZ

Re: uneven point gap as dist is rotated
 

I was reusing what I thought was a good used shaft and had the same problem, after going thru all other possible causes I tried a different shaft which fixed the problem, must have been from that bad batch.
Derek, most of the wet here on my manor is coming out of a can, we sure could use some of your rain.
Regards Brian.

Re: uneven point gap as dist is rotated
 

Brian Ill deliver some in Feb, ?? My devise is a clamp that fits on the dissy, with various hole in the side of which your dial gauge fits in, can measure point gap, cam run out , etc, that's how we picked up out of round shafts only where the cam fits on, this area has been machined down to take the cam ,

Re: uneven point gap as dist is rotated
 

Ahhhhh.........so that's what those slots are for in the V blocks.....

Re: uneven point gap as dist is rotated
 

Also check the distributor cam with a micrometer... Most repro cams are not made accurare on the lobes. Try to stay to an original parts.....hope it helps

Re: uneven point gap as dist is rotated
 

Hmmmmm ! Good Post! I am having some ignition issues that seem like they may be caused by this too. But I said" nahhhh, that couldn't be!" But I see now how it could be. Just bore the hole in the cam a couple of thousandths off true center and she will not ever run right! Sloppy machine work will do it every time!
Terry

Re: uneven point gap as dist is rotated
 

Find someone with a Distributor machine,..it solves a ton of problems.
I've used mine for the past 40+ years....

Re: uneven point gap as dist is rotated
 

this thread makes me wonder how they ever kept these cars running 85 years ago. must have been wizards with that tool kit.

Re: uneven point gap as dist is rotated
 

85 years ago they were new and they also had genuine Ford parts
to repair them not Chinese junk.

Bob

Re: uneven point gap as dist is rotated
 

The model A was built for the common man . The common man could understand and do things that most of the people that now have model A's can't understand or do.