Can't get timing right, can the oil pump gear be off by one

[Halfdunn]

Been trying to time my 230 Cu In and just cannot get it right. Pulled distributor cap at #1 on TDC Compression stroke and the rotor points to about the 5 o'clock position. # 1 plug wire goes to the corresponding tower on the cap as the rotor points to. I have read somewhere else where you remove the oil pump rotate the distributor drive gear counter-clockwise by one tooth and reinstall until distributor points to the 7 o'clock position on #1 TDC Comp stroke.

As it is right now I cannot adjust the distributor enough to get to the right setting of 2 before TDC- 6 after TDC. Distributor hits the adjusting bolt on the adjusting plate.

All of this because it cranks and runs fine until 4th gear and is flat on power then Revs fine, just no power on small inclines. Carburetor has been cleaned and points and coil test appropriately.

Any help appreciated.

[Cal_Gary]

Hi Half,
No, there is no "one tooth off" on an M37 distributor. It has the offset tang if your distributor is Military; the tang (like a flat tip screwdriver) is centered if you have a civilian distributor.
I recall an ancient post here about the rotor setting alignment with the cap contacts being off.
I'd shoot Charles at M-Series a PM-bet he knows what I'm talking about.
Good luck!
Gary

[greeno]

Thought @ #1 TDC the rotor should be at 7' oclock?

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[NAM VET]

while I have no suggestion for your gears tab engagement, there are two timing adjustments for the distributor cap, a "coarse" one under the cap, and the fine one, which is Turing the whole distributor one way or the other. You may be able to get closer to your timing by changing the amount of "swing" of the whole distributor by changing the coarse adjustment. NV

[scott k]

I have come across this before in a m38a1 jeep. The oil pump gear was not timed right with the cam and through the spark plug wire position on the cap off and made timing the engine difficult. Had to do it by ear. I corrected it all when I rebuilt the engine.

[mike_m]

U can be off timing wise due to gear being off 1 tooth or more on oil pump. When I replaced my oil pump my timing was off like yours and once I removed the oil pump again and rotating the gear back another tooth and reinstalled it was good. I believe the engine rebuild manual covers how to install oil pump correctly
Has ur oil pump recently been replaced? If so then IMO that is likely the reason timing is off.
Good luck

MikeM

[Halfdunn]

Thanks everyone for your help in my dilemma. Sorry for the late reply as I attended a GA MVPA event near Atlanta this weekend.

I firmly believe I will need to remove the oil pump and move the gear counter-clockwise one tooth. I have not had the pump disassembled since I have had the truck for almost four years. I am aware of the finite and major adjustment point of the distributor and to no avail not enough timing change. Even with the #1 cylinder at TDC, rotor still points at the 7 o'clock position in the distributor.

Will get into the oil pump soon after a couple of more Veterans Day parades and some MVPA events in Florida.

Thanks again and will post back here what I will find.

HalfDunn

[Kaegi]

7 oclock is the correct spot for number 1. do you have the distributor and wires in the correct orientation? did someone move the wires into the wrong spots on the cap?

[Halfdunn]

Yes, the distributor is oriented correctly. Yes, the wires have all been moved one position counter-clockwise in the distributor. Rotor points to 5 o'clock currently. That is my reasoning for the oil pump gear to be off by one tooth. Not the offset slot in the end of the pump shaft.

Crazy thing is it runs great, cranks easy but just does not have the ummpf under load uphill. I know it is a power limited motor in these things but cannot get the timing adjusted for some top end power.

Thanks.

[Monkeywrench]

I had the same problem - couldn't get the timing right. it's a six cylinder 4 stroke engine, which travels 2 revolutions before #1 fires again. 2 revs is 720 degrees divided by 6 cylinders = 120 deg of crank rotation per firing pulse. The distributor runs by camshaft gear at half speed of the crank, so it only travels 60 degrees for each firing pulse.

There is not quite enough room to swing the distributor the full 60 degrees to get the timing right if it is timed wrong to the camshaft (through the oil pump gear drive)

Fix it

1. Put the #1 cylinder on TDC (top dead center).
There's a 1/8 inch pipe plug in #6 cylinder for probing TDC. #1 and #6 pistons travel together, so if 6 is up, so is 1. If compression pressure is coming out of the #6 1/8 pipe plug hole, then turn the engine one more turn to get #1 on TDC compression stroke.

2. Now unbolt the oil pump, slide it out and turn the gear and reinstall so that rotor button points to 7 o'clock. Ensure offset tangs match.

3. Now turn distributor to middle of coarse and fine travel range. Install cap, find plug hole @ 7 oclock on the distributor and you'll put #1 plug wire here and install the rest of the wires 153624 in order. When bolting oil pump back to block, watch for broken gasket or replace it.

[Cal_Gary]

(Bumped due to tardiness in approving the post-sorry Monkeywrench!)
Gary

[Halfdunn]

Well, I finally got around to getting my timing right. I could not have done it without the help from this group. With #1 cylinder at TDC on compression stroke, my rotor was pointing to the 5 o'clock position in the distributor. I could not get enough adjustment by moving the distributor to get anywhere near 2 BTDC of timing.

I followed your suggestions and removed the oil pump and turned the geared shaft one tooth counterclockwise and replaced it while turning the distributor rotor to the 7 o'clock position. Reassembled everything, put the timing light to it and got it adjusted to the 2 BTDC. New plug wires also helped ($300 from VPW) it to run properly I feel. Before it was somewhat sluggish and now it seems to be a more smooth even acceleration to my top speed of about 43 mph. By the way it has a rebuild Depot tag on the motor from 1970. I can only guess it was assembled back then with the timing off from the Depot.

Thanks again everyone, you are the BEST!!!

[NAM VET]

if your truck tops out at 43 mph, have you checked your compression? My rebuilt engine is 120 even on all cylinders, hot motor, plugs out, throttle pedal to the floor. I can quickly pull 50 mph, but rarely attempt that, as it is just not good nor safe for my carefully balanced engine. I think it would eventually get more than 50 mph, but I won't attempt that. I think my truck's best cruise speed is right at 40 mph, seems to be right at the torque peak I guess, climbs hills best at that speed. But glad you seem to have your timing solved. Could your engine be running out of fuel to go faster?

Do you have a clogged fuel filter, or weak fuel pump? Proper set on your needle and seat? But good to have your engine better. Hal

[UZIS9MM]

Nam Vet,

He may be running a stock carb with the governor still set to 45mph. My truck has the governor set to 45mph and that's it - no faster, no matter how much I push on the petal. I have never messed with it, nor do I wish to. 45mph is just fine for these older engines and the gearing that these trucks have.

Kevin

[NAM VET]

come to think of it, my truck zips up to 45 so quickly that I just assumed it would continue to accelerate to higher than that. Maybe it wouldn't with my stock carb. Maybe I have seen my speedo going down hill or something. I think next time I am on the road, I will see how fast it will go, but not risk much over 45 or so. Hal