Ok can someone lead me in a direction on this one. What I have is an erratic spark on my timing light, I checked several wires and they are all eratic.. nothing is a constant atleast for long. Now these are brand new accel 8mm spiral wires and I just installed them, checked the ohms and they are all 1700 or below (good). Tonight we replaced the Cap, rotor, and coil on my HEI and that did not solve the problem. The car runs ok, just misses here and there.. nothing too bad though.. but I would like to get to the bottom of this spark problem.. can someone give me any ideas? Thanks

Do you mean the timing light shows the timing marks moving back & forth? If so, you might have worn bushings in the distributor (shaft moving a little off center) or the oil pump teeth might be chattering a little bit (worse on some engines than others) and cause the timing to be unsteady. The timing would have to jump around quite a bit to cause a misfire. What kind of engine is this?

Keith

Well its the light itself that seems to be on mark with the markings on the balancer, its just that the light is not consistently ticking... it stops here and there.. and the light is good... Its a 355 with HEI, iron vortec heads, edelbrock RPM intake with a Holley 3310 750cfm on top...

Does anyone have any ideas on this?

I have a couple of ideas. Did you check the pick-up wires, usually green and tan for a break at where they go into the pick-up.?? A common fault caused by the vacum advance movement and after a while the wire breaks. This can cause some weird missing and or stalling conditions. Also check to see if the ground connection from one of the four screws that hold the HEI coil in place. This wire will connect to the center pin on the cap snout. One other thing, make sure you put dielectric grease on the sealing washer between the coil and the cap, were the carbon contact goes. I have seen cases where the spark jumps around the washer without the grease. I was spinning one on the sun distributor machine just last week for a customer to get a baseline on what advance was in it, and watching the scope I had connected to the cap. Bingo, one problem the guy was having showed up, ie, it was cutting out and missing time to time. Good luick!!
Shawn,DZ-302, owner, Franks Performance Auto
1969 Z-28, matching#s, 51/51, M22, 3:73s
1967 SS/RS 350, matching#s pg, ac, owned 31 years!!

What I have is an erratic spark on my timing light,
You do not meantion that u have any noticable problems with the car its self.
Assuming this is it case..
I suspect you timing light is either defective or a cleaper brand. Cheaper brands are not as robust as more up grade timing lights...they have a tendency to cut out and be intermitent when the trigger is held down..Holding down the trigger also results in perminent damage, giving intermitent flash

Shaw, thanks for the tips.. I am going to check those tonite.. I thank you for the input.

Ok can someone lead me in a direction on this one. What I have is an erratic spark on my timing light, I checked several wires and they are all eratic.. nothing is a constant atleast for long. Now these are brand new accel 8mm spiral wires and I just installed them, checked the ohms and they are all 1700 or below (good). Tonight we replaced the Cap, rotor, and coil on my HEI and that did not solve the problem. The car runs ok, just misses here and there.. nothing too bad though.. but I would like to get to the bottom of this spark problem.. can someone give me any ideas? Thanks

I just bought a Craftsman timing light (not cheap) with that same problem. The light flashes erratically when you pull the trigger. In the instructions it states if the light flashes erratically that... that is a sign of a low voltage problem or a dirty inductive pick-up or the inductive pick-up not clamped properly on the spark plug wire.

I've had this problem too sometimes. Seems the BIG wires kinda spread the jaws of the pickup and it just triggers erratically. I used to tape em closed, or as close to cloesed as they'd get on an 8mm wire, but now I just ignore it.

Possibility?