Timing dimple always right?

[midgetracer]

If the timing gear was forced on 180 deg off, the valves would be out of time wouldn't they? The alignment of the cam and crank gears are only for piston/ valve timing. Setting the distributor to TDC is only setting the distributor to fire when the piston is up on the compression stroke. Also the crankshaft dictates that when #1piston is up, #4 is also at the top and 2 and 3 are at the bottom of the cylinder. I am sure the dowels were not on the piston tops in Commander Toastys Engine.

 

[Purdy Swoft]

If the timing gear was forced on 180 deg off, the valves would be out of time wouldn't they? The alignment of the cam and crank gears are only for piston/ valve timing. Setting the distributor to TDC is only setting the distributor to fire when the piston is up on the compression stroke. Also the crankshaft dictates that when #1piston is up, #4 is also at the top and 2 and 3 are at the bottom of the cylinder. I am sure the dowels were not on the piston tops in Commander Toastys Engine.

You are right, both counts.

 

[Tom Wesenberg]

Ron/IA,

If you are talking about my experience, the Timing Gear was forced onto the two alignment pins backwards, so the dimple was 180 degrees off. When they originally assembled the engine, they probably simply did not use the timing pin and timed it by placing the #1 cylinder's piston at TDC during assembly (before installing the head). The engine does not care where the dimple on the timing gear is. It will run fine as long as it is timed correctly. The dimple on the timing gear is there to make it easy to find TDC... which it does as long as it is installed correctly. In that case, the guy who rebuilt that engine failed to note the instructions that are on page 1-51 or 1-138 of the Model A Mechanic's Handbook.

I'm confused as to the orientation of your cam gear.

180* off would denote rotational positioning, which would not be possible without redrilling one of the holes for the alignment dowels. Backwards would denote having the front of the gear face the rear of the engine. I just tried this on my engine in the basement and found the gear would then rub on the engine block, because the hub of the timing gear is offset from the center line of the gear teeth, so this doesn't sound possible either.

Was your gear installed backards, so the timing dimple faced the rear of the block?

 

[Tom Wesenberg]

If the timing gear was forced on 180 deg off, the valves would be out of time wouldn't they? The alignment of the cam and crank gears are only for piston/ valve timing. Setting the distributor to TDC is only setting the distributor to fire when the piston is up on the compression stroke. Also the crankshaft dictates that when #1piston is up, #4 is also at the top and 2 and 3 are at the bottom of the cylinder. I am sure the dowels were not on the piston tops in Commander Toastys Engine.

If the timing gear was off by 180*, the cam would still be in time because the crank gear comes around twice for each revolution of the cam gear.

It would be impossible to install the Model A cam gear 180* off on the camshaft, unless you redrill the alignment dowel holes.

Distributor timing doesn't enter into the cam timing, because you can simply loosen the distributor cam screw and set the timing anywhere you want.

 

[MCHinson]

You guys obviously have much more experience with Model A Engines than I do. I do not represent myself as an engine expert. I do a lot of work on Model A Fords, but I am not an engine rebuilder.

In the interest of brevity, let me try again to answer the original question, "Is the timing pin always right?"

The timing dimple is almost always right, but based on my experience... not always.

I once had a Model A that the timing dimple was not right, either the timing gear was forced onto the alignment pins incorrectly when the timing gear was installed, or the dimple was drilled 180 degrees off when the timing gear was made. It drove me crazy for days. If I ever have significant trouble timing a Model A Engine again. I will not spend days trying to time it using the timing pin. I will physically see that the number one piston is actually at top dead center on the compression stroke.