The Stovebolt Site Forums The Shop Area Engine Shop Timing ball jumping around

Tonight I attempted to adjust the timing on my 53 1/2 ton GMC and noticed the timing ball was jumping around. It was moving left and right about 2 ball widths. I tried to search here for an answer but could not locate a similar thread. What could be causing this?

Also, when I start the truck I can hear a clacking noise. I read several threads that recommended using a little marvel mystery oil to clean out the guide paths. Where would I squirt the oil? In the cylinders?

Thanks for all your help,
Dale

Check the top of the distributor shaft to see if you can shake it side to side. It sounds like the point gap/dwell is changing due to distributor shaft wobble from a worn upper bushing, which is changing the timing. For every degree of dwell change, the timing changes two degrees. At higher speed, the timing will appear to stabilize.
Jerry

What technique did you use to set the valve lash?

Jerry, Yes I can move the distributor back and forth about an 1/8".

Tim, I don't know what the valve lash is and I don't know the techniques to set it.

What would be my next step?

Dale,

Here is one technique for adjusting valve lash (the valve stem to rocker arm clearance) on a 216/235/261 mechanical lifter (solid lifter) engine.

Here is the Shop Manual technique for valve adjustment.

I found the rivet that holds the vacuum advance to the stamped metal piece clamped to the distributor had elongated its hole. This allowed the distributor to advance and retard uncontrolled a couple of degrees. Ended up drilling the rivet out, re-drilling the hole to make it round and using a 1/4" shoulder bolt.

I had two spare distributors and both were worn the same way, I’m wondering how many others have found the same problem

I probably didn't make myself clear about what to check. It's OK if the rotor can turn back and forth a little- - - - -that's the centrifugal advance working, which is normal. If the shaft can shake side to side, more than just a little, it will allow the point gap to change. If that's happening, the only fix will be to change the shaft bushings, or swap for a better-condition distributor. Also check for the sloppy vacuium advance linkage connection, which would cause the same kind of problem.
Jerry

Thanks to eveyone. I will check things tonight.

I will put a pry-bar with a 6 foot cheater extention on it to see if I can move the distibutor back and forth....(no just joking). . Just having a little rookie fun.

Hey Kip,

I assume you are talking about the rivet pointed to by arrow "A" in this picture http://i824.photobucket.com/albums/zz168/dinlow/1953%20GMC%20before/Distributor.jpg. I know this shows a screw, but its a picture of a later model distributor. Is that correct?

Dale

Jerry,

I attempted to shake the distibutor from side to side and front to back. It was solid. No movement.

Dale

Also, I looked at the vacuum advance. I did not see a rivet anywhere. Is it at the back of the distributor?

Dale:

Yes the rivet is the one at "A" When I held the distributor cap and rotated it there was a degree or two of rotation before the link to the vacuum cylinder began to move. I'm kinda surprised that the rivet and the bracket to the distributor base are not hardened in that area. It seems there is a lot of ware as this area rotates slightly every time the vacuum advance moves, and that happens every time the gas pedal is moved in either direction. It is also the only thing that holds the distributer in place.

i believe the side to side movement they are talking about is between the distributor and distributor shaft. that will change the point gap as was mentioned. turn the engine slowly untill the points are opened, or trying to open; if they dont open it could be because the distributor shaft is too far to one side (worn distributor bushings) @ that point, see if the point gap can be changed by just moving the shaft.

Thanks. I have to admit that is not what I was shaking. I am going to re-check the rivet hole and shaft again tonight. I am confident it will be one (or both) of these things.

I am trying to set the timing in my 53 3100 and cannot see the steel ball through the flywheel hole. Should I just move the dist until I can see it, then set the timing from there? Also, I don't see any kind of pointer in the flywheel hole?

Are you looking through the hole just above the starter? There's another hole in the driver's side where you won't be able to see anything. Try rolling the engine over by hand and shining a bright flashlight through the hole in the bellhousing. Once you find the ball, highlight it with a drop of white paint. Sometimes the flywheel is dirty enough it's hard to see the markings without a pretty aggressive cleanup.
Jerry

You fixed my ignorance Hotrod Lincoln....I was looking through the hole on the driver's side.....thanks.

I am trying to set the timing in my 53 chevy with 216 motor and having a little trouble.....I can't seem to get the ball to stay on the pointer after I tighten the nut. Do I remove the vacuum advance from the carb and plug the line to set the timing? Any other ideas as to what I'm doing wrong?

Remove the vacuum line at the advance, and plug it. If the idle speed is adjusted right, there shouldn't be any vacuum on the line, but it never hurts to be sure. If the idle speed is too high, the centrifugal advance will start to operate, and that can affect the position of the ball. Try to keep the idle down to 500 RPM or slightly less whille adjusting the initial timing.
Jerry

Now I'm in time...thanks Hotrod Lincoln!