Timing issue ?

['68 C-20]

I Picked up a 67 C10 4x4 to use for a yard/Plow truck. It has set since spring without running, but I got it going pretty easy.

292, B model Carburetor. It was running rough so I set about to pull plugs, cap etc. Got everything cleaned or replaced as required and still runs rough. Starts pretty quick, just runs rough.

Each plug had an identical "burn pattern" so I know each cylinder is more or less on equal ground. Have not done a compression test yet.

I can pull each plug wire while it is running for each cylinder and make it sputter more or less the same, so I know there is nothing catastrophic inside the top end.

It idles a little rough, balks and spits when you step on it, like the timing was off, if I hold a high idle (about 1500 RPM or so) it run OK but you can hear a cylinder or two dropping in an out.

I chalked up the timing marks and threw a timing light on it, and could not find the timing mark, no matter how I adjusted the timing. Then I went around the motor looking for the mark with the timing light and found it at about 10 o'clock on the wrong side of the Harmonic Balancer. (Yes I was clipped to the No 1 Cyl.)

When I dialed in the distributor cap so it ran as good as I could get it by ear the No.1 plug on the distributor is not at the front of the Distributor where it should be but back where No.4 is supossed to be, No.5 is in front. So sumpin' is outa' whack by 'bout 60 degrees.

Any thoughts? Did it jump a timing gear?

[unclewatts]

Sounds to me like the outer ring on your crank pulley might have slipped.

[LONGHAIR]

Originally Posted by '68 C-20

When I dialed in the distributor cap so it ran as good as I could get it by ear the No.1 plug on the distributor is not at the front of the Distributor where it should be but back where No.4 is supossed to be, No.5 is in front. So sumpin' is outa' whack by 'bout 60 degrees.

Any thoughts? Did it jump a timing gear?

There really isn't a place where it is "supposed to be". The number one terminal of the cap could be anywyere, as long as the rotor it pointed that way when the combustion cycle starts.

"Jumping" the timing gears is virtually impossible. They are direct gear driven, no chain to jump. It is possible to break some teeth...but that would be a catastrophic thing.

You need to confirm the timing mark at TDC.

['68 C-20]

Originally Posted by LONGHAIR

There really isn't a place where it is "supposed to be". The number one terminal of the cap could be anywyere, as long as the rotor it pointed that way when the combustion cycle starts.

"Jumping" the timing gears is virtually impossible. They are direct gear driven, no chain to jump. It is possible to break some teeth...but that would be a catastrophic thing.

You need to confirm the timing mark at TDC.

I thought that was the case on the timing gears, thanks.

To confirm TDC, Run Number one Cylinder Piston up to TDC on the compression stroke and see where the timing mark lies?

Would it be possible for someone in the past to have removed the Harmonic Balancer and put it back on several degrees off?

['68 C-20]

Originally Posted by unclewatts

Sounds to me like the outer ring on your crank pulley might have slipped.

I think you hit it dead on. Thank you for the reply.

I pulled the plugs did a compression test while they were out, 125 to 145 all cylinders. So I know there is nothing wrong inside to contribute to the rough running.

I ran No. 1 up to TDC and just put a new mark on the crank pulley.

I have not run into a crank pulley slipping before, the rubber must be oiled up.

I think for now I will put it back together, set the dwell, points and timing to the new mark, check for Vacuum Leaks and pull the Carb to rebuild and see if that will smooth out the motor.

Question, it is a yard truck so should I bother to repair/replace the crank pulley? Could it actually come off? Weiging in at a few lbs I would not want it spinning around under the hood free at 2000 RPM's.

[LONGHAIR]

It's the outer weighted ring that slips on the inner hub. It can't really slip off (as in flying loose) because the belt pulley holds it in place.

[westofb]

I would think it could slide to the reargetting into the front of the motor. Most like if that happened you could get it shut down before it damaged too much. Pretty sure you would here a lot of noise when/if it happens....reminding you to turn off the key.