Misfire especially notiable above 1500 rpm

[rustybottoms88]

The company actually makes a transparent cap! http://www.topstreetperformance.com/ign ... -1880.html

[rustybottoms88]

You really can't, if you want to be certain. Buy another cap, the usefulness is much greater than the cost.

You can quickly check three things with that cap: that the rotor is pointing exactly where you want it, that the rotor is not fluttering back-and-forth relative to the crank position, and that the rotor isn't changing its nominal (mean, median, average... define that as you want) position across the rev range.

I got my clear cap in and put it on. It was well worth the money. I phased the rotor and then put a light on it. The rotor is fluttering back and forth at 1500rpm and above. It is Rock solid at idle. I guess I need a cam and distributor gear.

[billr]

Does the cam gear also drive an oil pump? If so, is the driven gear on the dizzy shaft or on the oil pump? When the driven gear is on the dizzy, I wouldn't expect any amount of wear to effect the spark scatter much. The load from the pump keeps the gear (on the dizzy) tight against the cam gear; all backlash is taken out. Now, if the driven gear is on the pump, then the dizzy can flop around as much as the slots/tangs between dizzy and pump allow. New gears there aren't going to help any. Are you sure your vacuum and centrifugal advances (if any) are locked solid?

[rustybottoms88]

The cam gear does drive the oil pump through the cam gear. I have been very busy this week. I hope to have time to double check that the distributor is locked and that there is no play or moment in the shaft/connection between the rotor and the dizzy gear.

[rustybottoms88]

I double checked the dizzy to be sure it was "locked out" and it is secure. See the self tapping screw in place.
I put a timing light on it again and indeed the rotor is fluttering. I am not sure what else it could be besides the slop in the gears? But as you say the oil pump should take that out. But at these higher rpm it is certainly fluttering. I am so close to driving this thing.....

[billr]

That does not look "locked" to me! the top-most plate, with the two inner pins for the springs, is part of the dizzy shaft, correct? Will the rest of that stuff rotate any relative to that dizzy shaft?

[rustybottoms88]

No none of it will rotate. I took the top piece off you referred to, to show that is indeed locked. I also took the advice of a friend and added a selftappin screw opposite the other I had put in to lock the dizzy. His theory was that the screw was throwing off the balance of the rotor bug and that the slop in the cam and dizzy gear was rearing its ugly head because of it.


Problem solved! The misfire is gone. Thanks bill for your help. I was almost ready to tear the front of the engine apart to replace cam and dizzy gear. Glad I did not now and thanks to you for pointing out the oil pump buffering the slop. And thanks to my friend Lee for his twin screw idea.