Another botched distributor installation corrected

[Gary C.]

Re: Another botched distributor installation corrected

If I install distributor gear 180 deg from rotor and install rotor 13.8 deg CCW from factory position, then I have to move housing 13.8 deg CCW to get in timing. I could move all wires 45 CCW, then I have to move housing CW 45 deg from 13.8 deg CCW position or 31.2 deg CW from factory spot. So VAC is either 13.8 deg CCW ahead or 31.2 deg CW behind from factory position for the 180 deg off gear/rotor. Either way, barring interference with firewall or ignition shield supports, the distributor housing can be turned to give desired timing advance.

Had a fellow with 70 Corvette that had the VAC in front of the ignition shield support and he had to use a 90 deg adapter to get the tach cable to work. A lot of trouble for an initial issue of 180 deg off gear/rotor and putting the VAC/tach drive in right spot.

[Duke W.]

Re: Another botched distributor installation corrected

On a C2 small block if you install the gear 180 out the VAC will contact inlet the manifold with only about 8-10 degrees initial advance. That's insufficient for a SHP/FI engine with only 24 centrifugal. So you move it a tooth CW. Now the VAC hits the coil bracket with too much initial advance. Al this point the usual advise from so-called "experts" is "move the plug wires one position one way or the other"... whatever. Now you've fallen inside the event horizon of a black hole and are lost forever.

Been there, done that over FIFTY years ago! Live and learn! I've lost track of how many screwed up distributor assembly/installations I've corrected in the last 50 years, but I left a trail of happy owners who could barely believe how much better their car ran after I left my fingerprints on it.

Duke

[Frank D.]

Re: Another botched distributor installation corrected

I added a vacuum advance distributor to my 270hp dual quad 61 car (they don't come with one stock) and had to play games with the location so as not to hit the stock aluminum manifold or ignition shielding; reclocking the wires as part of the solution. There were no ill effects and it let me dial in the advance curve nicely. Not something I would do unless needed nor as a stop gap though.

It is also my understanding that the rotor tip should be aligned with the end of the lower gear roll pin that points between two of the helical gear teeth as the "dimple" convention may not be adhered to in all cases.

[Doug C.]

Re: Another botched distributor installation corrected

And to add more fuel to the fire... anyone have a copy of the service bulletin referenced in the attached image?

[Lawrence M.]

Re: Another botched distributor installation corrected

C3 Distributor Alignment.jpg

I think this is the Service Bulletin you are looking for. I do not know why it attached sideways. Never had an attachment do that before.

[Doug C.]

Re: Another botched distributor installation corrected

Thanks for posting the Service Bulletin. That information did not make it into the 1970 Service manual which shows the conventional layout for SBs. I wonder when the factory started to deliver cars using the alternate configuration? The 73-74 judging guide photos show the vac can in the alternate configuration for both the SB & BBs.