bouncing timing mark

[dukcaln]

so went to adjust the timing finally and it seems that the timing mark is bouncing all over the place when you put the timing light to it, am I missing something or what should I be checking... what can cause this

[mrhino]

Prolly a wore out timing chain

[hjewell2]

More info please. what type of springs in dizzy HEI? aftermarket?
Cam type? RPM during reading? vac advance hooked ETC.

[mrhino]

Sorry just realized it was a fresh engine. Disregard my earlier statement.

[crazy longhorn]

The mechanical curve could be a little loose? Does she dance @ idle, or revved up? crazyL

[dukcaln]

its a mallory set up and it dances at idle.... I can post the exact mallory set up in the morning...

[72lb4x4]

I'm a dumb ass, so I think in simple terms.

What can be wrong?
Distributor
Cam
Timing chain and gears

Now its multiple choice...

[dukcaln]

Originally Posted by 72lb4x4

I'm a dumb ass, so I think in simple terms.

What can be wrong?
Distributor
Cam
Timing chain and gears

Now its multiple choice...

always one of those

[D.PASSMORE]

Check your timing light plug/connection, I had same symptom, timing light cable to gun was loose. I taped in place and worked fine.

[GRX]

If using an induction type timing light place the clamp over the wire near the spark plug, and away from other plug wires.

[jocko]

check for a leaky vac advance rubber hose perhaps (assuming your light is good - excellent point d.passmore)

[Lee H]

This is more than likely timing scatter. There are a few things that will cause this. The most common cause is excessive distributor shaft end play. If there is excessive play in the shaft, the shaft will bounce up and down, advancing and retarding the timing. Shim the shaft to about .007 - .0100" endplay. Make sure to put the cam gear back on right, with the dimple facing the same direction as the rotor contact. I find that Moroso part number 26140 has a good selection of shims. Slop in the breaker plate attachment point. The distributor breaker plate is located in position with a hole for the vacuum advance control unit rod. This hole gets sloppy, and the plate bounces around. Find a different plate with no slop or lay it on a flat surface and whack the hole with a hammer to tighten the fit up and remove all slop. Bad distributor bushings can also cause this. If the bushings have slop and the shaft has lateral movement, timing will be erratic. So yank the distributor out and tighten it all up and you will have rock solid timing. Lee

[dukcaln]

grx, now that you mention that I did move the clamp once further away from the headerds which would have put it away from the other wire and it seemed to not dance as much, so it made me puzzled... I have them tired and routed together... so that is something I need to check. I will also post up pictures of my set up.... thanks

[hjewell2]

Just throwing something out to members.

Degree your balancer.

Take a tape measure and measure across the balancer from the front get that measurement. lets say 8in now x by 3.1416 divide by 360 x the total timing you want lets say 36* now take that total which would be in this case 2.51 inches over from zero mark on your balancer make a mark. bring up to 3000RPM use zero on your pointer turn dist until mark lines up to pointer. you are set with total timing.

[dukcaln]

so thats how you figure out total advanced timing?

[hjewell2]

Originally Posted by dukcaln

so thats how you figure out total advanced timing?

Yep unless you have a dial back timing light.

[mr48chev]

New out of the box distributor or a bought used distributor? When I worked in a shop in Texas that ran a couple of dirt track cars and the boss was one of the best there was at setting up a distributor in the Sun distributor machine I saw a lot of guys show up with 3-4 year old Mallorys that they had bought used from racers only to find out that the distributors were pretty well worn out. Did you have the distributor set up in a distributor machine?

This time though I think it has more to do with your timing light and maybe the way you have your wires routed and or tied together than the distributor it's self. If it is a Sears like the two I have check the connection between the cables and the light. Then as someone else said check the clamp and maybe move it to a spot away from the other wires. You can also put it on #6 plug wire and it should show the timing mark the same as #1 would.

[dukcaln]

update, well went out and routed the wires better and totally seperated the front wires. started the truck and took out the timing light and checked the timing. to my amazement, the mark was steady..... went and adjusted the timing and all seems good now..... want to thank all of you for posting your thoughts and ideas and your own trial and error's. which is why we post things on the boards.... gives us a direction we may not realize to look in.....thanks again

[GRX]

Cool deal. Suspected it was a signal interference issue. Been there before myself.