What could cause the timing marks to constantly move?

[kustomkyle]

Is there a vacuum advance on a 1987 distributor? I looked everywhere and can't find a vacuum hose, there's just electrical wires attached to the distributor.

I don't think there is vacuum advance either. I guess just pre-1981.

 

[jamesejam]

Is there any allowance for play on a distrbutor rotor? When the car is off, I can move the rotor with my hand about 1/4 inch. Is this normal, or is this why my timing fluctuates?

 

[kingcolbert83]

If you can move it by hand them I'm leaning more toward the distributor being loose as to what is causing the problems. It could be that the bolt has been tightened down so much or overtighted that its stripped. If you can move it by hand then it will move when driving.

 

[pontiacgp]

are you checking the timing with a digital timing device or are you using a timing lite?

 

[marcar1993]

Is the retaining bolt tight? As for your timing, you need to jump the a&b terminals in the diagnostic port while the car is running to set the timing. (Top row, 2 most right terminals) If you don't you'll be off big time. Read the emmisions tag on the fan shroud for tune up instructions.

 

[85GPLef41]

I would double check the timing chain for any slop. My old 305's chain was really stretched and it had about 73 thousand miles on it.A old mechanic told me how to check it by taking the distributor cap off and then putting a breaker bar on the harmonic balancer and turning it and the rotor should turn with it as well. My rotor wasn't turning in conjunction with the balancer being turned.
My timing was really off too in order for it to run right.

 

[pontiacgp]

That's a nice simple method to check a timing chain..