Distributor End Play 0.076"

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   Is that a record?  Do I win a prize?   From a 73 CJ5 304, a Motorcraft of some type.  So much play I wonder if a thrust washer was misplaced, either on top or bottom.  Gear doesnt look bad in so far as the wear pattern is centered and not deeply worn.  But there is pitting on wear points so should probably change it while fixing the end play.  Which worries me given all the tales of mangled cam gears and distributor gears. 
Also, the arm for the vacuum advance is very sloppy in the corresponding hole. Seems like that cant be right.  Timing must have been all over the place on this one.  I never put a light on it, just adjusted by ear. 

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ChillyB Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Nut Joined: Nov/14/2018 Location: PA Status: Offline Points: 371	Post Options Post Reply Quote ChillyB Report Post Thanks(0) Quote Reply Topic: Distributor End Play 0.076" Posted: Mar/23/2019 at 1:54pm
	Is that a record? Do I win a prize? From a 73 CJ5 304, a Motorcraft of some type. So much play I wonder if a thrust washer was misplaced, either on top or bottom. Gear doesnt look bad in so far as the wear pattern is centered and not deeply worn. But there is pitting on wear points so should probably change it while fixing the end play. Which worries me given all the tales of mangled cam gears and distributor gears. Also, the arm for the vacuum advance is very sloppy in the corresponding hole. Seems like that cant be right. Timing must have been all over the place on this one. I never put a light on it, just adjusted by ear.

PHAT69AMX Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5919	Post Options Post Reply Quote PHAT69AMX Report Post Thanks(0) Quote Reply Posted: Mar/23/2019 at 2:28pm
	Have seen more, factory wasn't real tight on endplay. Opinions vary, don't make it too tight. Note, the "Dimple" in the Dist Gear is meant to line-up with the Rotor tip. May want to reload some fresh Hi-Temp grease in the top bushing grease well.
	Link to a Short YouTube Burnout Video

74Bubblefender Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Charter Member Joined: Jun/29/2007 Location: The AMC form Status: Offline Points: 2589	Post Options Post Reply Quote 74Bubblefender Report Post Thanks(0) Quote Reply Posted: Mar/25/2019 at 11:52am
	Once you put a shim in there the gears have become very prone to failure until they find a new wear pattern. Do not shim it until you know you will be running it for a few hours on a warm day.
	We are just about to forge new AMC V8 crankshafts.. please check here http://www.bulltear.com/forums/showthread.php?19564

ChillyB Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Nut Joined: Nov/14/2018 Location: PA Status: Offline Points: 371	Post Options Post Reply Quote ChillyB Report Post Thanks(0) Quote Reply Posted: Mar/25/2019 at 12:03pm
	With engine running is the distributor shaft drawn up or pushed down? How does the weather affect gear break-in?

Trader Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6881	Post Options Post Reply Quote Trader Report Post Thanks(0) Quote Reply Posted: Mar/25/2019 at 1:38pm
	On acceleration the gear is drawn down, on deceleration it is pushed up. AMC did not spec a distributor shaft end play but most every other manufacturer does at typically 0.008" to 0.015". I believe, without having to dig this up again, that 0.015" is 1/4 to 1/2 degrees of distributor timing when rotated. A manual transmission will show more wear at the bottom if the driver downshifts a lot. I'd "guess" it was a standard transmission. Typical wear is more on the bottom but at 0.076" you should definitely look at the top. As a "guess without looking at it", a 0.015" on top and a 0.050" on bottom should get you were you need to be.

ChillyB Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Nut Joined: Nov/14/2018 Location: PA Status: Offline Points: 371	Post Options Post Reply Quote ChillyB Report Post Thanks(0) Quote Reply Posted: Mar/25/2019 at 3:23pm
	I suspect with the heavy load of the oil pump that the distributor gear is always loaded the same way.

ChillyB Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Nut Joined: Nov/14/2018 Location: PA Status: Offline Points: 371	Post Options Post Reply Quote ChillyB Report Post Thanks(0) Quote Reply Posted: Mar/25/2019 at 3:53pm
	Ok, I think the distributor will always be driven uphill, so if I shim a sloppy shaft at the gear end only I'll be moving the gear downward from its current pattern. My distributor did not have any shims at the top between the housing and the breaker plate. Should it? In fact, the breaker plate has been riding on the aluminum rim of the grease cavity, but apparently not much given the light wear pattern. Another reason I think the distributor is loaded uphill during engine operation. So do Delco Remy points distributors sometimes have shims on the gear end, AND under the breaker plate? At this point I'm thinking to shim just the top, and I dont know if it matters. More I think of it the more I believe the distributor will always reference to the position with shaft pushed uphill while the engine is turning, even while cranking at startup.

Trader Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6881	Post Options Post Reply Quote Trader Report Post Thanks(0) Quote Reply Posted: Mar/25/2019 at 4:11pm
	There was no shim at the top from factory. The "goal" is to reference the gear center lines so you have the most tooth engagement. If the distributor gear rides high or low, it will not engage at the same depth as center. If you have little to no wear at the top then just shim the bottom. 0.010" off the cam gear CC is not going to make a huge difference in gear engagement but this is a inverse square thing. For every doubling the distance the gear is off center you reduce contact 4x. Edited by Trader - Mar/25/2019 at 4:29pm

ChillyB Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Nut Joined: Nov/14/2018 Location: PA Status: Offline Points: 371	Post Options Post Reply Quote ChillyB Report Post Thanks(0) Quote Reply Posted: Mar/25/2019 at 4:57pm
	The gear would have to be off by 5/16 or more to get off the edge of the gear. If the goal is to land on the existing wear pattern then I'd say one could shim the top, or do nothing. After thinking about it a bit I think the wear pattern is formed with the shaft pushed up hill into the distributor. And I also am starting to believe the factory didnt fuss much about end thrust becauae it doesnt matter. The shaft will always, and only be pushed up into the distributor while running. The only advantage to removing the slack from the top is to keep it from dropping when you shut it down so it doesnt need to push it back up when starting. Maybe this saves a revolution or three on startup. Otherwise the timing is slightly retarded until the shaft gets pushed up.

Trader Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6881	Post Options Post Reply Quote Trader Report Post Thanks(0) Quote Reply Posted: Mar/25/2019 at 5:37pm
	Your engine, your call. Article from an engine builder (I believe he is talking distributor gears) SD, there are more on the Jeep forums: On some engines it is absolutely critical to get the clearance spot on. One of those is an AMC 360. I had one come to my shop that was eating cam gears like candy. Ten mile tops it would be ate up and so far out of time it wouldn't run. It was amazing. I got it as a basket case, so it took a little time to figure out. The previous owner had replaced the factory distributor with a rebuilt. The rebuilt had something like 0.100" slack in it. I had to shim it down to less than 0.015" for the gear to live. The gears are so small on the AMC that even a slight mis-alignment killed the cam gear. So it can be a critical issue depending on the engine.