I've finally got my 1978 280z idling decently... Kind of. It's been really touch and go. My distributor has been doing this weird thing where it starts making a grinding noise and then stalls the engine. Doesn't do it 100% of the time, but when it does, it's typically when I rev the engine or attempt to put the car into gear. This is leading me to believe that it has something to do with the oil pump or spindle rod or something. I've attached some photos of my old distributor cap and rotor and you can see where there's been interference between the rotor and cap. I have since replaced the cap, but continue to experience the same issues. Any thoughts? Anyone seen this before?

IMO, it's either bad dist. bearings allowing side play in the dist. shaft or a bad rotor. I had a cheap cap and rotor in my 521 that ended up looking like that. New Bosch products cured it.

Mine used to wobble as the shafts do get worn - you can see it in the video below.

But it never - as far as I am aware - interfered or made grinding noises. Try to do what I did with mine in the video and see if you have more movement than I did. (And that was my old engine where the PO went wild with the blue paint!!) [emoji849]

If I recall right there are different size distributor caps out there.  I think that the ZX cap might be a hair smaller.  If you put your 280Z cap on a ZX distributor it might be loose.  Or if you went to the auto parts store and asked for a 78 280Z cap, but you have a ZX distributor.  A possibility, I think.

14 hours ago, Zed Head said:

If I recall right there are different size distributor caps out there.  I think that the ZX cap might be a hair smaller.  If you put your 280Z cap on a ZX distributor it might be loose.  Or if you went to the auto parts store and asked for a 78 280Z cap, but you have a ZX distributor.  A possibility, I think.

I'd be surprised if that was the case. How might I tell?

15 hours ago, AK260 said:

Mine used to wobble as the shafts do get worn - you can see it in the video below.

But it never - as far as I am aware - interfered or made grinding noises. Try to do what I did with mine in the video and see if you have more movement than I did. (And that was my old engine where the PO went wild with the blue paint!!)

 

Mine is similar. Is that bad?

Yes, not good

Mine is similar. Is that bad?

 Well chap, my tuner who prepares race cars said it was, hence my path to the 123 dizzy as the play in the shaft can cause spark scatter / inaccurate timing at high engine speeds. At 6k rpm that thing is spinning 50 times per second!!    

 

The RockAuto Cardone remanufactured one I bought wasn’t much better. While the bushes can be quite easily replaced (there was a guy in the US that made them) the shaft itself gets worn. So unless you can get a new shaft, you will always have some play.

 

I’m a geek so for me it eventually mattered.

 

The only way to get rock solid high speed timing IMHO is crank triggered systems but it all comes down to what you want from your car and how much perfection matters ;) I’m learning the hard way that sometimes, good enough is good enough! But for me it’s more than about driving the car, it’s about giving myself “something to constantly tinker with” - read headaches!!! ;)

 

 

 

 

 

 

 

34 minutes ago, AK260 said:

 Well chap, my tuner who prepares race cars said it was, hence my path to the 123 dizzy as the play in the shaft can cause spark scatter / inaccurate timing at high engine speeds. At 6k rpm that thing is spinning 50 times per second!!    

 

The RockAuto Cardone remanufactured one I bought wasn’t much better. While the bushes can be quite easily replaced (there was a guy in the US that made them) the shaft itself gets worn. So unless you can get a new shaft, you will always have some play.

 

I’m a geek so for me it eventually mattered.

 

The only way to get rock solid high speed timing IMHO is crank triggered systems but it all comes down to what you want from your car and how much perfection matters ? I’m learning the hard way that sometimes, good enough is good enough! But for me it’s more than about driving the car, it’s about giving myself “something to constantly tinker with” - read headaches!!! ?

 

 

 

 

 

 

 

Well for me, it's just important for it to at least run right now. And that interference is causing the engine to stall I think.

1 hour ago, moozieman said:

Mine is similar. Is that bad?

I found that there is a certain tolerance between the rotor and each contact. I'd be surprised if it was that simple, but ill check that as well.

What is the significance of the vacuum lines leading up to the distributor? Could that pose any issues?

2 hours ago, moozieman said:

I'd be surprised if that was the case. How might I tell?

Wiggle the cap.

What is the significance of the vacuum lines leading up to the distributor? Could that pose any issues?

Check the size of tour cap as mentioned above - it could be that your 280z cap is just that bit different to the 280zx one.

The vac line provides a “load sensing” function. When wide open throttle, the vac drops to zero and advance becomes “base timing” + mechanical advance. When the throttle is closed or part closed the vacuum increases and the distributor adds vacuum advance. This is because the mix is leaner and needs more time to burn.

That last bit sounds counter intuitive but think of it this way: you have two plates with a dusting of gun powder that you will light with a match from the centre of each plate. One has a light dusting (lean) with large air gaps between particles, the other has a thick dusting (richer) with much smaller gaps. The one with the larger gaps between each particle will need longer to fully burn across the plate (hence you need more advance). So when cruising, or idling, you have more vac, leaner mix and therefore need more (vac) advance to get a full burn.