Mike

In the throes of tracking down the rattle/tapping noise, I inspected my rotor. I had replaced it (and the cap) two seasons ago. The old rotor was destroyed during removal, BTW.

Anyway, I can grab the rotor and move it around some (in/out, CW/CCW) on the shaft. Not a lot, but a lot more than I think it is supposed to. The set screw, though cranked down (as far as it goes I think), never really seems to tighten the rotor down. Doesn't seem right...

I did not use any "glue" (never new I was supposed to until I ran into this board).

Any ideas?

Sam Lin

There is a screw holding the rotor on its shaft, and a screw holding the shaft on the cam end - did you check both?

Sam

Mike

The rotor is turning/moving on the shaft (the shaft does not seem to be moving relative to the cam)

As I said, the set screw holding the rotor to the shaft was tight. I cannot be sure that it was fully bottomed out previously. I couldn't tighten it without bending the allen wrench I was using.

What bothers me is that it seems the design relies upon the screw somehow squeezing one side of the rotor's internal metal bushing against the shaft. There's no keyway or something else more precise, just a single screw. So by definition the entire rotor is shifted to one side (just a bit, but still).

If that's what the design requires, am I supposed to tighten the living crap out of that set screw? I fear breaking it off in the shaft...

Sam Lin

Did you try removing the screw and seeing if it was too long, and maybe bottoming against the other side of the shaft before the head bottomed against the rotor face? The rotor and shaft are a tight fit to begin with, the screw just works in shear to prevent rotation, and should not need gorilla tightening. The tolerance is also tight enough that any out-of-roundness is negligible and doesn't affect operation.

Sam

IceShark

I'm in the same position and will get to replacing the rotor when I finally figure out my balance shaft alignments.

My rotor had some sort of varnish layered on between the shaft and inner rotor surface. It had a yellow tint, maybe from age and heat. Then some blue loctite (the medium strength grade) on the set screw, which took a fair amount of effort to remove. I'm going to wire brush the set screw threads and put more loctite on it. I'm not sure what to do about the varnish between the shaft and rotor. Guess I'll just leave it alone as I would hate to have the thing glued on there for ever.

Danno

Yeah, the exact placement & rotation of the rotor isn't really that critical. That's because it's more than wide enough for the spark to get across. You'd need a rotor that's off by over 20-degrees before you'd have any spark problems. But the wobbling is a problem because it can allow the rotor to hit the cap and increase the gap the spark has to jump.

On this particular car with the following rotor, it dynoed with the same power figures before & after replacing the rotor:

Peckster

Pull the rotor to see if the screw protrudes from inside. Maybe it's not long enough.

Mike

Wow, that's quite a nasty rotor! The one I just replaced was bad, but not like this.

Seems, in my case, when I replaced that "bad" rotor, the screw had only "felt" tight - the threads had enough junk in them to bind up before the rotor was held completely tight. After cleaning the screw a bit and reinstalling, the rotor now sits tight.

Normally I wouldn't have worried much (afterall, I had a pretty ugly rotor and it ran fine) but I am trying to track down a tapping/knocking sound coming from the general area of the distributor. It wasn't this...

Peckster

Make sure the dust cover behind the rotor is on tight. Mine was loose once, I had to snap it back into place

Mike

Though one cannot inspect it to be sure, the dust shield seems to be OK...

Once the shield is oriented properly, I found I could gently "****" it (twist it) a bit so that the tab (at the top) kind of "snugs" into the notch in the distributor housing, holding the shield in place while I remount the cap.

At least I've now got the cap installation down to a science.

Mike

I received a new distributor cap gasket from Pelican - what a difference. Everything is tight now.

Flight_951

Is the gasket different than the plastic dust shield? My cap is slightly loose too. I have a new cap and new dust shield. TIA

KLR

I'm surprised that a car would run at all with the rotor in Danno's picture. Does replacing a worn rotor truly impact the way a car runs, or is it more likely the new plug wires or cap that restores some performance/smoothness if all of this stuff is old/worn?

Danno

The wires probably make the biggest impact as far as degrading performance. Cracks in the wires will arc your spark towards the block