29 Model A :replacing timing gear, aluminum or phenolic? How to determine oversize

[Greg NE Ohio]

New to Model A: the timing gear has missing teeth, should I go to aluminum or phenolic. And how to determine if to go to the oversized gear 3/5 ths
Thx

[Kurt in NJ]

By how it fits— the backlash checking at several points rotating the crankshaft, the wear on the crankshaft gear was sometimes compensated by oversized gear and sometimes for the alignment of the crankshaft centerline.
Ideally both gears (crank and cam) should replaced

[WHN]

I have always replaced with the phenolic gear.

I have never used an oversized gear even on a high mileage engine. My feeling has been that if the crank gear is that worn, both should be replaced.

Enjoy.

[JayJay]

Hard for me to see how a phenolic cam gear can wear a steel crank gear. Last engine I built had 0.016” backlash with the old phenolic cam gear, a new phenolic gear brought that down to <0.003” and it’s running great. Yes, I can see on an improperly mothballed engine with corroded teeth on the crank gear might be cause for replacement, but absent visible wear or pitting I would not routinely replace the crank gear.

[daveymc29]

Dave Mc Eachern makes a great set of gears for our A's and T's. Bronze is quieter that the aluminum ones, I'm told. Want to build a nice Burtz with a set of Mc Eacherns gears. I may even want to go with and overhead like the Miller if my horse can run a few seconds faster, but poor devel he is also aging and I fear the doesn't bode well for running faster. May have to sell him and apply the 3 cents a pound I get to the project.
Dave

[jeepguy1948]

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I don’t know if a “plastic” gear can wear a steel gear but I sure remember how deeply rubber shoes had worn tracks into the concrete stairs at the (then) 40 year old elementary school I went to.

[JayJay]

Originally Posted by daveymc29

Dave Mc Eachern makes a great set of gears for our A's and T's. Bronze is quieter that the aluminum ones, I'm told. Want to build a nice Burtz with a set of Mc Eacherns gears. I may even want to go with and overhead like the Miller if my horse can run a few seconds faster, but poor devel he is also aging and I fear the doesn't bode well for running faster. May have to sell him and apply the 3 cents a pound I get to the project.
Dave

I have a set of McEachern gears for my Burtz, haven't built it yet. They are really lovely to look at and I'm told perform even better.

[Herb Concord Ca]

If replacing the gear, I vote for an aluminum gear, that what I installed last year. Otherwise, you will be replacing the fiber gear again in a few years.

[Terry Burtz, Calif]

Oversize or undersize timing gears are needed when an engine rebuilder locates the main bearings either too close or too far from the camshaft.

[lrf]

I installed an aluminum timing gear and it is noisy compared to the original I replaced. Your choice.LRF

[nkaminar]

My aluminum timing gear is very quiet, along with the rest of my car. I just turn off my hearing aids.

[stevests]

His first name is Dan & you'd be hard pressed to locate a better matched set of timing gears !