Engine Timing Gear Cover Recognition
 

Relative to the location of the ignition timing pin hole, there are different front engine covers for the Model "A" & various "B" engines. These covers are similar castings except for the location of the ignition timing pin hole. When you have an unknown cover in hand, the question arises, "Is it a for a Model 'A' or one of the various Model 'B's'"?

The photo contains the timing pin hole location for a Model "A" cover. The pin hole is 1.38" center-to-center from the bolt hole that is situated just to the side & below it.
I do not have a Model "B" cover handy to measure its pin hole location. However, if someone will post the corresponding dimension for the Model "B", I will amend the photo to show it.
In the photo with the 4 covers, note the difference in timing pin hole locations between the Model "A" & Model "B" covers. The pin hole location in the Model "B" covers is 9.5 Camshaft Degrees above the location of the Model "A's" timing pin location. Why is there a difference? Because unlike the Model "A", the Model "B" distributor has an automatic spark advance system.

Re: Engine Timing Gear Cover Recognition
 

Re: Engine Timing Gear Cover Recognition
 

Vince Falter as usual does an excellent job of reverse engineering to explain how stuff works and why there are differences. My intention is provide a handy reference dimension to enable easy / quick differentiation of the timing covers. I have often picked up a cover at a meet, i.e. Hershey, and was unsure of which cover I had in hand.

Re: Engine Timing Gear Cover Recognition
 

The cover you have marked as the B service replacement timing cover is actually the production Model B (i.e. 1932) timing cover. The cover you have marked as the "production" cover is the Model 40 (1933-34) timing cover.

Look at the position of the front motor mount in relation to the crankshaft on your "production" cover and your "replacement" cover. They're dramatically different. There's no way you could substitute one for the other in the same car.

Re: Engine Timing Gear Cover Recognition
 

alexiskai, I revised Post #1 to reflect your corrections. Thanks for letting me know. Did I get it right?

Re: Engine Timing Gear Cover Recognition
 

Looks good to me. You may or may not want to add the ‘28 A timing cover. These show up frequently at swap meets.

Re: Engine Timing Gear Cover Recognition
 

Thanks. This explains a lot! I have not been able to detect ANY hole/dimple in the timing gear for setting timing. Frustrating! I have been reduced to measuring the distance between piston top and the spark plug opening for TDC...and have not been delighted with the accuracy. My timing jobs have worked pretty well but I keep thinking that they could be slightly better.

Re: Engine Timing Gear Cover Recognition
 

I've always just used visual clues to figure it out. The timing hole is between 2 bolt holes. If it's closer to the the lower one it's an A cover. On the B cover it's closer to the upper bolt hole.