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MG MGA - installing tach drive gear on new cam

I have installed the tach drive gear on a new camshaft as part of an engine rebuild. The gear has about 1mm (.040") movement along the cam axis. The old gear/cam had zero axial play. The difference seems to be a slightly wider slot for the retainer ring on the end of the new cam. Is this ok, or should I make a shim to take out this movement?
Thanks! George

G Goeppner

George,
If the gear is a snug fit on the cam shaft, I would probably leave it as is. However, if it slides easily on the cam shaft I would make a shim for it to take up the slop. I think it would not be a problem either way, but I don't like loose stuff inside my engines.


Ed Bell

Shouldn't the woodruff key make the gear a good tight fit on the camshaft anyway? Mine was a good tight fit (the machine shop pressed it onto the new shaft for me)and the circlip is really only there as a "just in case". I wonder if you need to fit a new woodruff key and carefully file down the flat edge of the key until it's "just right". Maybe someone will correct me if I am wrong.
Lindsay Sampford

I was able to pull off the gear from my old camshaft without too much effort, I didn't have to press it off. I fit the new cam/gear/key assembly to have a similiar sliding fit. I'm just not sure if the small amount of axial clearance I now have on the new assembly is ok or not. I'm inclined to make a shim as Ed suggests.
G Goeppner

Hi George, there is no shim shown on the parts list. Barney's web site suggests that the gear is a tight enough fit on the camshaft as to require a puller to get it off. Make sure that there is no sloppiness of the gear on the shaft because if the gear chatters against the key for long enough it will wear the keyway in the shaft and the gear. A spot of "Loctite 641 bearing fit" would stop it moving on the shaft.
Lindsay Sampford

Every one I've seen has required a puller to get it off and a hammer to put it on. The gear should NEVER move on the shaft, because it if did the key would soon become badly worn and might fail. If the gear is loose on the shaft, either shim it for near zero end float, or use a drop of bearing set adhesive to eliminate the radial clearance and lock it in place.
Barney Gaylord

This thread was discussed between 08/06/2009 and 09/06/2009

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