MTFCA Forum

Howdy Everyone
My TT died a couple years ago on the way home from the local parade.
Family issues put the repairs on the back burner until now.
It appears the generator was binding up and the generator gear ate the Alum timing gear.
I ordered some parts and cleaned as much of the alum shaving from the engine as i could.
Now it's time to install the new timing gear on the cam shaft.
I know the timing marks on the cam gear & crank gear must line up.
It appears the gear can be mounted to the cam in two positions.
As I recall from working on motors from the 1950-1970 there was an indexing pin that only allowed the gear to be in only one position.
I don't see anything to stop the gear from being installed one way or to the other position 180 degrees.
Looks like the dowel pins don't care where they are located.
I haven't found any markings yet on the cam.
Am I overthinking this? Seems it makes a difference for the valve timing?

Welcome to the Forum Dave

gear mounting makes makes no difference in timing or function in any way

You are recalling a "convention" of how it SHOULD be done by the book, but for an in-line 4 it matters not. The crank goes 'round twice for every cam rotation. Other engines it can matter, and because of that they will be keyed in such a fashion as to be impossible to do wrong.

Now, what you DO want to be careful of, is to correctly center the timing cover over the cam such that the camshaft is DEAD CENTER to the timer boss so that you don't throw inter-cylinder spark out of whack any more than necessary (hopefully not at all). After the new rope seal is in place, that will require a purpose-built centering gauge and almost certainly some hoofing and poofing and grunting while you bias it one way or another while tightening things down.

Oh and Dave

I addressed your question regarding installing the gear, but gear replacement is just treating the symptom (a ruined gear). Now you need to find out WHY the gear was ruined. Hint: it is because your generator gear was meshed too tightly to the cam gear...a portion of the generator mounting bracket to the block is to be SHIMMED with a couple paper gaskets if necessary to bias the center/center location of the generator gear to the cam gear so that there exists a small amount of lash. Get this done while the timing cover is off.

Thanks guys!
Scott, I replaced the generator, pretty sure it was the problem. It was difficult to rotate by hand the entire rotation and seemed to be 'very tight' in one spot each rotation, while the new generator spins freely with my fingertips.
Thanks for the caution on the crank seal.
I got Grandkid duty this weekend, so hopefully next week get back working on the TT

Again thanks for sharing your knowledge!

It is sometimes necessary to shim out the generator mount to get the correct generator gear to cam gear clearance. I had to use two gaskets on the generator mount to get proper gear engagement. Also check the condition of the generator gear so it doesn't do the same and damage the new timing gear.

After dealing with wife's health issues, I'm back looking at the Model T.
New cam & generator gears installed. Lash on the Gen gear to crank gear is good.
I assume the lash on the cam gear to generator gear should be the same? less than .003?

GoldToyBox wrote: ↑

Sun Oct 01, 2023 7:24 pm

After dealing with wife's health issues, I'm back looking at the Model T.
New cam & generator gears installed. Lash on the Gen gear to crank gear is good.
I assume the lash on the cam gear to generator gear should be the same? less than .003?

As long as there is some lash between the generator & cam gear, you are good to go.

"less than .003" and you are on the edge of having issues. Our shop standard is .004/.006" backlash. On T generators you need to really careful that the generator bracket is dead square to the front of the block. There is nothing in the design to make it straight when bolted up. Best way is to temporarily install the front cylinder cover and then bolt up the generator bracket to the front cover and then install the side bolts in to the block.
This will square up the bracket pretty well. The gear lash can be increased by adding a thicker gasket. Just FYI, a .010 thicker gasket will increase the backlash pretty close to .010".