Can't Advance Far Enough with Pertronix

[Paulporsche]

I have a 74-77 distributor in my car, even though the engine is from an SC. The distributor rotor turns CLOCKWISE. It has also been recurved by the original builder to suit the 3.2L displacement mod.

I have installed a Pertronix Ignitor in place of points. When setting the timing I have the distributor turned all the way counterclockwise so that the adjustment nut is all the way at the left end of the slot, so I can't advance it further. The sketch shows the current approximate config.

The problem is, I need more advance, something like 20 degrees, but I can't get it because there is no more clearance in the slot.

I'm thinking I may need to move the rotor 1 tooth in order get the distributor back in the correct range of adjustment.

So, the question is, on a 74 distributor, if I want to get more advance, can I move the rotor 1 tooth and which way do I move it? Back--ie counterclockwise and against the distributor rotation, or forward, ie clockwise and with the distributor rotation? BTW I think I've tried both ways and couldn't get the engine to fire but I'm so confused now I want to start fresh with it!

My initial thought is to move the rotor foreward ( direction of spin) effectively "backing up the distributor" so it will then be able to turn more if required to get more advance

Alternatively, will changing the Pertronix gap make a difference, as it does with points gap? If so, do I go smaller or larger?

[47silver]

Remove and reinstall one gear towards advance

[gomezoneill]

That drawing looks pornographic.

[cmcfaul]

Pull the whole distributor out and rotate it one gear tooth clockwise.

Chris

[Paulporsche]

Chris may have hit on why my previous attempts at rotating the gear didn't work: I was rotating the gear/rotor but leaving the distributor in the same location, not rotating both the same amount, thus keeping the relationship between the two the same! His description which suggests keeping the correct relationship between rotor and ignitor the same but repositioning the distributor relative to the slat makes so much more sense.

Thanks for that Chris. I'll try it tomorrow morning.

[Paulporsche]

Thanks to Chris and 47Silver. Once I rotated the whole distributor, not just the rotor shaft, I was able to get the advance I needed.

[911pcars]

Why do you need 20 deg. advance at idle?

[Paulporsche]

Originally Posted by 911pcars

Why do you need 20 deg. advance at idle?

Advance @ idle is 9 BTDC with vac retard disconnected, which equates to TDC or 1 ATDC with vac retard connected.

Recurved 77 distributor with vac retard only.

The 20 degrees I referred to was that I needed 20 more than I was able to get with the distributor in the original position.