Distributor Drive Gear

farmerdick

farmerdick

Senior Member
Hey Guys, The pin for the sleeve that goes over the distributor drive shaft was sheared off and half a dozen teeth on the dist drive gear were laid over flat last week on my way home. I got towed home. I was advancing the spark lever and going up hill at the time. I don`t know as yet what the teeth look like on the camshaft. The engine is out of the car now and waiting to be torn down for inspection. This engine was rebuilt last winter with a .330 lift on the camshaft. Any ideas as to what might have caused this to happen?

Richard/Maine
 
Did the distributor shaft or drive gear shaft seize up? I can't think of too many reasons for your trouble. I remember a problem years ago with the repro drive gears but can't remember what the problem was. I would bet your cam will be ok.
 
Many people driving modern cars dont realise that the "A" requires much more maintenance than their late model.The dist should have the oil cup filled every 500 miles or they will eventually seize,or at the least make quite a noise.,and yes you want to retard the spark if going up a steep hill.Some years ago the drive gear for dist was made with a pin holding it to shaft .original gears were made in one piece with the shaft-another lousy repro part.Hopefully it didnt damage the camshaft gear.
 
The distributor would also be my first guess, but also check the oil pump to be sure it's good. I don't know why the collar pin would be sheared, as the collar has no torque or pressure put on it and the pin simply holds it in place.
 
I currently have a thread going search “engine noise”. My cam is walking “fore and aft” with a consistent dull knock, mostly noticeable at idle. The car runs great all kinds of power. It too, is newly rebuilt. One thought was to just drive it and hope it stops (ya know make it or break it) but I really don’t want to break it, over some easy fix. I ruled out the distributor first, I pulled the valve cover, visually everything looks good, I removed the drive gear unit and disassembled. The gear spins freely in the sleeve except for one spot that seems a little gritty there is no discoloration of the shaft or sleeve due to heat. That was when I noticed that the bore, on the gear end of the new sleeve is off center. I think this would affect the mesh to cam gear. I will be reassembling using the old sleeve. Using a long screwdriver through the distributor hole I spun the oil pump, it spins freely. Lastly I will check the cam plunger and spring.
 
Check the length of the plunger spring. I had a short one in when I checked. Luckily I had the right one to install which eliminated the hammering knock. I am using grease like Tom Wesenberg does for the distributor for assembly after rebuild. Just less of it. Bob
 
fordgarage said:
Since the plunger and spring is what controls the cam walking, I wonder why you did not check that first? :confused:
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With the cam door off, I did applied pressure to back of the fiber cam gear as close to the cam as I could. It did not budge. This is probably not a viable test of plunger spring strength, but it was enough to make me continue in a different direction. I really don’t like the gear end of the bearing housing off center. I do not think it would rotate in the journal once installed, but if it is installed so the gears are meshing tightly they could get hot. I will try to measure and/or post pictures as to the degree this bore is “off”, maybe it is not an issue. I remember reading some where about spacing the plunger with washers to decrease the endplay between the cam and plunger when fully compressed. This would definitely prevent the cam from walking and potentially mask a problem. I just want to make sure I have minimum resistance on the cam.
 
Sorry if I changed this thread from Rich’s problem, to mine. My main intention was to offer what I found when inspecting the drive gear assembly. I appreciate your patience, time and input, as I am new to Model As. I’ll continue the discussion of my car on “engine noise” thread. Thanks…
 
flatheadkev said:
I currently have a thread going search “engine noise”. My cam is walking “fore and aft” with a consistent dull knock, mostly noticeable at idle. The car runs great all kinds of power. It too, is newly rebuilt. One thought was to just drive it and hope it stops (ya know make it or break it) but I really don’t want to break it, over some easy fix. I ruled out the distributor first, I pulled the valve cover, visually everything looks good, I removed the drive gear unit and disassembled. The gear spins freely in the sleeve except for one spot that seems a little gritty there is no discoloration of the shaft or sleeve due to heat. That was when I noticed that the bore, on the gear end of the new sleeve is off center. I think this would affect the mesh to cam gear. I will be reassembling using the old sleeve. Using a long screwdriver through the distributor hole I spun the oil pump, it spins freely. Lastly I will check the cam plunger and spring.
Click to expand...

It would be better to fix the problem, than put a bunch of washers in there. Some thing is causing the cam to walk. Bad oil pump, or engine changed to pressure, dist shaft to tight, to much valve spring pressure, along with a high lift cam. Cam gears do not have enough clearance between them.
 
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