Distributor Grinding

[siteunseen]

Could you get a helper to make it do the grinding thing and then you listen around and see where it is coming from?  That's what I would try and you may already have.

It could be the water pump impeller rubbing against the front cover.  That's pretty common.  What about the sound with the clutch engaged/disengaged?  Listen around the alternator too.  They can make a grinding noise when you rev the motor.  It would have that black dust all over it also.

[moozieman]

21 hours ago, siteunseen said:

Could you get a helper to make it do the grinding thing and then you listen around and see where it is coming from?  That's what I would try and you may already have.

It could be the water pump impeller rubbing against the front cover.  That's pretty common.  What about the sound with the clutch engaged/disengaged?  Listen around the alternator too.  They can make a grinding noise when you rev the motor.  It would have that black dust all over it also.

It is 100% the distributor. I have put my hand on it while running and can feel the shaking before it dies off. The grinding sound is quite obviously coming from the distributor. There is also visible grinding under the distributor cap in the above photos.

[Zed Head]

Put your finger on the top of the shaft and see how much play there is.  Wiggle it and see if it moves far enough to touch anything.  Or just take the distributor out and see if there are any obvious problems.  While it's out see if the drive quill (down in the hole) has problems.

Your problem doesn't sound complicated but you're going have to go farther to solve it.  It's an uncommon issue, nobody out here will have the easy fix.  Time to take things apart.  Removing the distributor is super easy.  One screw, and disconnect the red and green wires, and it pulls right out.  It only goes in one way, so you can't really mess things up.

That distributor is so rusty inside that it's almost guaranteed that your vacuum advance doesn't work anyway.  

[jonbill]

Can you highlight where in the pics it shows the grinding? I can't see it. Also a sound recording might be good. One man's grinding is another man's whirring!

[moozieman]

21 minutes ago, jonbill said:

Can you highlight where in the pics it shows the grinding? I can't see it. Also a sound recording might be good. One man's grinding is another man's whirring!

 

[jonbill]

 

Thanks, I think that's the same pic I saw above - honestly, I can't see anything unusual. It looks like my distributor cap to me.

[siteunseen]

It could be a ZX rotor button under a Z cap?  I have know idea about the compatibility of those two but I do know a ZX has bigger cap and rotor.  It looks like your rotor button is too big to me.

If the shaft won't wobble I would do what Mark suggested and get the right combo from Bosch.  $10 maybe???

[Zed Head]

The parts look like 280Z parts if you compare to Rockauto pictures.

If moozieman is 100% sure that it's the distributor then there's only one thing to do.  Remove the distributor and check it out.  

The overall description doesn't really make sense anyway.  Why would the rotor grinding on the cap cause the engine to die?  The engine would happily just grind that cap and rotor in to dust.

[AK260]

.  Why would the rotor grinding on the cap cause the engine to die?  The engine would happily just grind that cap and rotor in to dust.

Actually that’s a fair point - I once forgot to put the clips on the cap and driving around I was wondering why the car wasn’t going as well! To this day I’m amazed it didn’t smash itself apart !!! But it did run and rev up.

[siteunseen]

I had the wrong cap on a Nissan D21 pickup, forever it seems now, that would jump spark and ran like garbage when I tried to accelerate too fast. It ran fine as long as I pampered the pedal.

[AK260]

 

Have you measured the length of the rotor arm from it’s centre point out and the same distance on your cap from the centre electrode out - using a digital micrometer?

 

Here is another thought - take the entire distributor assembly off. Put the cap on. Spin it by hand and see if you can feel scraping.

 

Next, clamp the dizzy vertically in a vice. Get a variable speed hand held battery drill, set to low speed and lowest screw-driving torque - such that the drill will stop easily if it encounters resistance. Now with a large flat screw driver bit in the chuck pushed into the bottom of the dizzy, spin it gently, then faster and faster. That way you can get a feel for any grinding, speed at which it occurs and how much resistance there is. Make sure you put some cloth into the tab at the bottom of the dizzy between it and the drill bit to ensure the bit doesn’t foul it.

 

 

Remember, 3k rpm is 25 rotations of the distributor per second, so when confident with the drill, get some speed on.

 

 

If indeed the rotor is getting caught, then it is probably advancing the timing to a crazy point that causes stalling. Having said that, (don’t ask why) on the old engine I’ve had an advance of 58 degrees at 3k rpm and no engine load without stalling or spluttering. Under load, that would have caused serious knock / damage and potentially would have stopped the engine running. Does yours spit through the carbs as it stalls?

 

I would say if your shaft is wobbly enough to cause this issue then you should see metal particles everywhere inside the cap and potentially damage at the pickup / star wheel part where the tolerances are tight. If not, then the grinding may be caused by something else in your distributor. I agree with Jon that your cap looks normal / like mine did. Don’t confuse the oxidisation / electrical plasma wear on the electrodes for physical scraping..

 

Let’s assume the cap and rotor are fine, so:

 

If it’s just happening when revving up, could the advance mechanism be faulty / have broken springs? Potentially, the advance weights are flying out too far, scraping the inside of the dizzy body and causing way too much advance. Doing the above drill test with the cap off would show this up as your scraping sound.

 

Also, put up a video of your shaft’s wobble (preferably the distributor shaft, not the one that will get you banned!) and let’s see how much it’s wiggling by. As you say, there are clearances / tolerances built into these things so the wobble you could see on my video - as horrible as it was - never caused grinding.

 

I’m showing you mine again, don’t be shy, show us yours ...