Timing gear failed, why?

30ccpickup

30ccpickup

Well-known member
I have a fiber timing gear in my Model A and the gear teeth are shredding. Replacing it should be no problem. I am more interested in what may be the cause of the failure and type and location to purchase a new gear.
 
You may want to check the condition of the crank gear..A rusted, pitted gear can eat a cam gear.. Replacing the cam gear is easy, the crank gear is another story..
 
30ccpickup said:
Replacing it should be no problem. I am more interested in what may be the cause of the failure and type and location to purchase a new gear.
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You are correct about replacing it not being a problem but it usually is a pain because the oil pan needs to come off to remove those little pieces of timing gear before they plug up the oil pump.

I think the failure is generally because the crank gear generally rusts slightly which abrades the fiber gear and wears it out. Also, the quality of the foreign-made fibers are 'suspect' at best!!

The aluminum gears that most dealers sell are generally manufactured by one manufacturer (Mark) and are of good quality. The only problem is most of the new alum. gears are manufactured oversized to compensate for a worn crank gear. The problem is the centerline set-up when pouring, and most better engine rebuilders using new crank gears tends to make a pinched gear when this oversized gear is used.
 
I have a fiber timing gear in my Model A and the gear teeth are shredding. Replacing it should be no problem. I am more interested in what may be the cause of the failure and type and location to purchase a new gear.
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Because they are no good. I never use them i buy the alum gear. If you buy another fiber gear buy the best one not the cheap one.
 
I have had problems with the fiber gears and as far as I am conserned all fiber gears are a problem waiting to happen. The best gears are the bronze gear from Dan McEachern and it is always best to replace timing gears in sets. I have used both the bronze and aluminum gears and they are pretty much silent and fail safe. Dan gears are available in undersize or oversize.

Possible causes of timing gear failure is . The babbit in the mains could have been line reamed out of line with the cam. The main bearing caps could be worn and filed several times to take up slack. Use of a fiber timing gear period. The use of aluminum or bronze gears will overcome any of these problems and should outlast the engine.
 
This maybe a silly question but how do i know if i need a oversize or undersized cam gear? I'm not much of a mechanic and very new to the hobby.
 
I would suggest you take the time to install a new crank gear; you can then make the decision as to what type of cam gear you want to use, or buy both in a set so they properly match.

I personally have always used a fiber cam gear, but always installed a new crank gear. I have never had a problem. The fiber gear runs a little quieter than the aluminum.

Ron
 
Go with the Dan McEacherns matched gear set if you want extreme bullet proof quality. You may want to contact him directly, if you just want to replace the cam gear seperately. I have them on one of my cars. Work great and quiet.
 
30ccpickup said:
I have a fiber timing gear in my Model A and the gear teeth are shredding. Replacing it should be no problem. I am more interested in what may be the cause of the failure and type and location to purchase a new gear.
Click to expand...

Is the gear that is shedding an old stock one? A few years ago I had a timing gear fail that had 5,000 miles on it. It was one that I had bought at a swap meet. Looked great but was obviously one of those "gyp" parts that Ford warned the dealers about. I replaced it with a laminated gear and haven't had any problems since. I have over 30,000 miles on it. If the crank gear is good and the gear isn't too tight, the cause may be just the quality of the gear.
 
I put a bronze gear in my coupe in 2006 with the radiator on. Here's what it looked like in 2010 - 4000 miles later.
 

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I think the preparation on the crank gear is important, if it is rusty, it should be wire
wheeled and not glass beaded, which I did on a customers Porsche, which then KILLED the new cam gear! Replaced the cam gear, wire wheeled the same crank gear and
every think is OK 15 yrs later.
Second, the pluses in a 4 cyl engine are such,and also with v/8, that the cam will
try to turn the opposite the rotation due to the valve spring pressure, and work on the cam gear causing a knock, when it starts to wear. Dudley
 
A fiber gear will also fail quickly if the engine has been mis-bored from true crank shaft parallism axis, to camshaft axis. The camshaft gear backlash should be about .003". Face of both gears should be parallel.
 
What are the symptons of a cam gear failing? I have heard stories of guys replacing them on the side of the road, but have wondered what were the signs of this happening, or how do you diagnose this when it actually happens?
 
We have switched to the bronze gears on all the Model A Times cars. We have over 25,000 miles on three engines with no problems.
 
Answering the post of Bick in New Zealand. Timing difficult to hold.....hence poor running engine after everything else has been checked. Possible noise that might be picked up with a stethascope. Or the worst thing would be......silence on the side of the road on a hot day other than for the cursing from yourself and your spouse telling you to be carefull of what you say because the children are listening.
 
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