MTFCA Forum

This is not my thread. Somehow the OP deleted his initial post.

Well I don't know what to do next. Second Magneto I have assembled. First one went together as it should, took a little shimming to get a .025 air gap. Second one not so much. Assembled the magnets to the flywheel using new spools. made sure all of them were in the same plane using a KR Wilson gap guage. Took some love taps to lower a few magnets Mounted the coil ring on the back of the engine, and with the gap guage, shimmed it just enough to make it level and the wilson tool hits every coil in the ring equal. I did not use the Ford shim or any other shims. I set the flywheel/magnets on the crank shaft flange with the transmission shaft in place just to see what I would need to do to reach the .025 air gap. I have no gap at all, the magnets hit the coil ring. Fresh engine, and the rear main has an equal amount of babbit showing on both sides. the magnets and hold down plates came of the engine. Any thoughts on what to do next?

I have aways told others it is not easy to set the mag coil. Glad to hear you are trying to deal with this. My recommendation is to:
Reduce the shims at each coil mounting by .035 in. and see what you get. Then adjust accordingly. Hitting the right shims is pure luck in my opinion. I have only done one. But it was successful.
Good luck.

Art Mirtes

Well yikes! Sounds like the babbitt for the thrusts may not be as equal as you think. At this point, with a fresh engine, take the rear cap off and turn it around, reinstall it and see if you can get any clearance.
The thrust is (with engine standing on its nose) pushing the crank to the front pulling the flywheel in the same direction closing up the gap between the magnets and coil ring bosses. As now installed, the babbitt may/must be thicker on the front of the cap and turning it may move the crank back to get clearance needed. The other option would be to build up the thrust and redo it making it thicker in the rear, moving the flywheel away from the block/mag coil ring.
If the crank has been ground with new babbitt and if that works, be sure to swap the shims side to side also.

Art M wrote: ↑

Tue Apr 16, 2024 5:44 pm

I have aways told others it is not easy to set the mag coil. Glad to hear you are trying to deal with this. My recommendation is to:
Reduce the shims at each coil mounting by .035 in. and see what you get. Then adjust accordingly. Hitting the right shims is pure luck in my opinion. I have only done one. But it was successful.
Good luck.

Art Mirtes

He does not have any shims installed as said in his post.

Thanks Mark. I missed the fact that he had no shims. Others will have better advice.

Art Mirtes

You have to consider the weight of the transmission when shimming. When it’s assembled to the engine vertically it will be OK BUT leveling out the engine on the engine stand will cause the transmission to droop. This does happen.

What to do???

If you have it at .025 vertical level and when you return it to horizontal you wind up with it touching the mag ring return to vertical and add shims on the droop end to get back close to a level clearance all the way around. It might take a few try’s to get it right but you’ll get there.

By the way the Ford Service manual has a section starting on page 84 paragraph 316 about setting the gap set correctly and what to do when the transmission weight causes misalignment. Hope this may help.

Turning the 3rd cap will more than likely lock up the crank, no line boring will put the cap in the centre.

Steve at langs tells me all spools are 3/4" tall. old spools may be less as they may have been beat down to level the magnets

The old practice of beating the magnets into submission with a hammer always makes me cringe. The idea of whacking the magnetism out of newly charged magnets persuades me that it's better to equalize them to within .003 with shims. With a prescribed gap of .025 to .040, I figure that's close enough.

Waldo wrote: ↑

Tue Apr 16, 2024 8:13 pm

Steve at langs tells me all spools are 3/4" tall. old spools may be less as they may have been beat down to level the magnets

Old spools even if beat down would not move the magnets far enough away from the coil ring to make a difference and new ones unless really messed up should be correct length.

Kerry wrote: ↑

Tue Apr 16, 2024 6:38 pm

Turning the 3rd cap will more than likely lock up the crank, no line boring will put the cap in the centre.

Most of my caps have enough slop in the holes that it might work. At this point he could try. The other option as I suggested would be to build up the back thrust and recut both ends. Adding to rear and subtracting from front.

John, he doesn't any gap now. So he needs to get that sorted out before worrying about compensating for sag.

This may have been overkill, but I took a little off some of the magnets to get them all the same weight.

Doug, You may have to make up a round shim to fit between the crank and flywheel with the appropriate holes for pins and bolts. Not my favorite way of doing it but might get you out of a tight spot in a hurry. Jim

Id start by removing the shims between the block and field coil. Under no circumstanes would I reverse the 3rd main. Youll loose a carefully crafted clearane. Id tell you how I know, that but I hate to see a grown man cry.

Doug,

As I read all of the posts I think you need to bring up the rear of the crankshaft but as it is a fresh rebuild block I would not change anthing to the block.
They only thing I can think about now, is that you will need to grind off some of the rear of the coilring mounting pads. Your coilring will go down and you can set the gap right with shims if needed.
Andre
Belgium

I turned my rear main cap around with no effects. There was plenty of slop in the holes for the captain move around. Not the best situation in my mind, but it turned out just fine. In my opinion that’s what I would try first because if it works it eliminates a lot of other modifications, that may turn out to be unnecessary or not the best.

My first action would be to evaluate the cranks position in the block. Confirm the 3rd main is the problem.
Is there the proper clearance for the crank to move forward & not hit the front main?
Does the crank gear fit within its limits under the cover?
Chances of turning the 3rd main around & fitting as is is nill. If it re-positioned the crank back, you will need some serious refitting, including time savering & cap grinding.
Another option is to build up the rear thrust surface on the cap & trim the front as mentioned earlier.
Then finally, the option of milling down the mounting surface as Andre suggested.
If milling, take the opportunity to square up the field coil if it had not been done yet.
Do a clean up cut on the mount face then turn over & do a minimal clean up cut on the 16 coil poles. Check for magnet clearance again.
Remove more material from the mounting face if necessary.

Is your KRW gage in calibration? Sounds like is not. If it was it would have told you what shims you needed.
You need the instructions on how to use it, they are in the Service Bulletins.

Just asking did you have a transmission shaft flange inserted between the flywheel and gap gauge then bolted to the flange/ flywheel when measuring the height of the magnets?
Courtesy of the Coilman, pictures from Toon!

When I look at the magneto gaping procedure I take into account ALL the factors that can affect the outcome.
The magneto magnet keeper to field pole gap is a function of two things. The gap set with the gauge AND the rear main bearing thrust end play.
KRW expected the rebuilder to 1) measure the crankshaft rear main thrust journal width, 2)add .004, 3) measure the thickness of the cast cap (or block journal casting if a 360 degree thrust will be used), deduct 2 from 1 and divide by 2 machining the front and rear thrust surface to that thickness. I don't know what procedure others use. The idea is to ensure the crankshaft is properly centered in the block and to make sure one side if the thrust surface is not too narrow thereby possibly failing early not to mention the proper relationship of the crank.cam gears.
Having done that you can now use a PROPERLY CALIBRATED gap gauge to set the magnet height and field ring position, but you have to ensure the crankshaft is not moving back and forth in the thrust gap when doing so.
This task is hard enough without additional variables that can affect the outcome.
Two additional things.
The Ford Service Bulletin fails to mention that to use the gap gauge for setting the magnet height you MUST have transmission stub shaft inserted in the flywheel counterbore before you install the gap gauge or you will be unable to use it.
Once the height screw is used and locked with the thumbnut to clear all the magnets the same height you cannot change it when setting the field ring position.
Ron

Are the magnets original to the flywheel?

There were different thickness magnets used in earlier engines.

"The old practice of beating the magnets into submission with a hammer always makes me cringe. The idea of whacking the magnetism out of newly charged magnets persuades me that it's better to equalize them to within .003 with shims. With a prescribed gap of .025 to .040, I figure that's close enough."

I just put the whole thing in the lathe and face off the magnet clamps and at the same time, a very light skim cut on the flywheel mounting flange.

Sorry John,
But the photo is from Toon Boer of the Netherlands.

Andre.
Belgium