Distributer/Oil Pump Clocking

[madmike]

I am putting the M38A1 engine back together after getting it back from the machine shop in short block form. I got it back set on TDC and after putting the major large parts on wanted to get the distributer in place to keep track of TDC. Problem is, the clocking of the dist. rotor is 180 degrees off. When looking at the oil pump, I noticed the casting does not exactly match the outline of the block. Is it possible that the oil pump shaft is 180 off, or the mounting? The pressure relief valve is in about the 8:30 position, pointing diagonally toward the block.

I played with the timing to ensure the engine is at TDC and the intake valve had just closed and the exhaust had not opened yet. It appears it is on TDC. A little more history. I bought this as a running engine but it did not run well and the previous owner had put a new distributer in. When I took the engine apart, it was not timed according to the manual. The wires and distributer clocking were different at that time but there was no evidence the pump had been removed recently.

If I have to change the oil pump clocking, is that a matter of just turning the gear or does it require disassembly?

Thanks for help and input. I did not think this was rocket science but it's turning out that way...at least for me.

[Balvar24]

Does it have points or breaker-less? I bought a non-running engine and someone had started but not finished a swiss conversion, thus putting it out of time.

[madmike]

It has points, and did run before but had no brakes and a leaking carb. Therefore I did not drive it, just ran it before the purchase. The previous owner is deceased and no historic info. was available. I could wire the engine to run okay as is but would like to bring it into original condition.

[RimfireJim]

Wouldn't this be caused by the oil pump shaft (not housing) being 180° off relative to the camshaft? With the engine at TDC, pull the oil pump, rotate the gear (and thus the distributor drive) 180°, and reinstall the pump. Now reinstall the distributor and the rotor should be pointing to plug wire No. 1.
-Jim

[wesk]

Try not to oversimplify the pump alignment.

1-The oil pump housing only fits one way on the block.

2-The cam drives the oil pump via their helical cut gears and the oil pump drives the distributor via their offset tabs at the ends of their shafts.

3-Unlike small block Chevies and Fords there is no 180 degree out program on a Willys 4 banger. The tang on the distributor is offset to one side and the slot in the oil pump shaft is offset to one side. This means they can only go together one way.

4-Step one on setting the relationship of the oil pump and distributor up is to bring #1 piston TDC on compression then back the piston down to 5 degrees BTDC. This is the firing position for the distributor.

5-Install oil pump so the small part of it's offset tang in it's shaft is about
7 o'clock as the helical gears start to engage and when fully installed the small side of the tang will rotate to about 8:30 o'clock.



6-Now install the distributor. It will only fit one way. The rotor will be pointing to about the 7 o'clock position.

[madmike]

Thank you all. I dropped the pump, rotated the shaft and everything lines up. This guy has been 180 off a long time judging by the grease build up that was on the engine and pump. Things are lookin' up.