I know when installing the field coil, the magneto gap should be checked, but how accurate are the one piece shims that Ford used? In other words, can a person expect the gap to be reasonably close if one of the factory shims are used?
I have found that I need the layered shims and put a different number shims under each bolt until I get the ring within the tolerances. I suppose in a perfect world where one has perfectly straight ring and every magnet and spool is just the same thickness it would fit with a one piece shim. Sometimes I start with the one piece shim and then work from there. Every magneto is a little different. The challenge is to get it as close as possible yet within the 25-40 allowable gap. The closer the better unless it is less than 25 then you run the risk of scraping. The wear on the endplay is toward the back, so starting with a close tolerance the magneto will continue to work for a longer period.
Terry; if you have your coil ring surface ground after being rebuilt it's easier because it's more uniform. When I've used my old rings it's taken more effort and I use the laminated, and there are different amounts under everything it seems. But if your mag ring is good and there is no reason to rebuild it the hassle is worth the dollar savings. You'll put the transmission on and off a lot, so a hoist with a sling really helps.
Norman is right about the gap. Get it as close as possible within the 25-40 range but leave some more on the underside of the coil ring, not for the crankshaft because you had to support it correctly with the fourth bearing but for the vibration of the coil ring on the underside.
I didn't now about these vibration but
Toon Boer, from the Netherlands, showed me last summer with his HCCT how the ring vibrates on the underside and what noise it makes when you crank the tester.
To maintain the gap from excessive end play in the crankshaft there was an accessory brass thrust washer that bolted between the front pulley and the block to control excessive end play
Please see the two threads from 2010 detailing my experience obtaining the gaps on my magneto and how many shims it took per bolt position to get a smaller gap at the top and a larger gap at the bottom. The number of shims you need, most likely will not be the same for yours, but it gives you a procedure by which to follow to obtain good results. For me, I started with full shims and peeled them off, one by one until the desired gap was achieved. The other thread shows the stand I made which assisted in safely keeping the engine vertical with it's tail pointed in the air, which assisted greatly. Jim Patrick
Terry, I had a stack of those original Ford one piece shims you speak of and I always used them when setting the gaps. I believe each one is 17 thousands thick so you could get in the ball park with them. I still had to shim a bolt hole or two to get things evened up. The one piece shims are a good starting point, though.
I just did this on an engine for my 24. I had the coil ring surface ground. My end adjustment was 25 on top, 35 on the bottom. I used a thick washer for shims. I did a little work with a flat file on the top ones. Simple, easy, and fast.
I also have used the original one piece shim on 2 of my cars. They were originally on the engines.
I did notice that after I got the rebuilt field coil from Wally the gaps were slightly different.
Using the 1 piece shim did help to get things in the ballpark faster (I think) even with using the slightly different field coil.
Ford used the one piece shim for a reason and it was probably because of speed of assembly at the factory.
Usually 1 shim is perfect.
I have seen those shims in many thicknesses. You about have to put the fly wheel on to see how much shim you need to start with.
Royce, unfortunately no one makes those shims you are showing.
Soda cans are about .005 and can be cut into shim shapes for fine tuning the spacing.
I bought a new set of spools for the magnets and then found there was up to .022 difference is the magnet thickness, which caused more grief.
A KRW-1 tool is almost always a requirement to get a good magneto setting.
I always begin with a shim that Royce pictured. I've never done an engine that didn't need one. There is an early and late style on these. I do as James mentioned above, except I use beer cans!