I've got a 1969 Corvette with a 390hp 427 that has a rare K66 transistorized ignition. Transistorized ignition is even more rare on a 390hp than 400hp or 435hp versions where it was much more common and required on L-88 cars.

My question is about the alternator socket position. I've looked at 100 pictures ob BB cars and some cars have the plug at almost the 12 o'clock position while others have the plug pointing down towards the upper control arm on the driver's side. TI cars had 61 amp alternators although I'm not sure if this was the same for non TI big block cars or if there is a difference in plug location between different big block alternator styles. Also my alternator restorer put the plug on top as well.

Is there something about TI specifically that changes the location of the alternator plug or is the rear case just rotated incorrectly? The main harness should be the same for all cars and the TI harness is totally separate so why tilt the alternator differently?

I got knocked on this in NCRS judging back before I knew about it, and I've seen some 435hp cars that are "top flight" in both configurations. I just want to know which one is right and why??

 

Hi sck,
I believe the 68-69 TIM&JG indicates that on BB cars with power steering the alternator was installed 'upside-down'.
Would that put the 'socket' in the position you describe?
Regards,
Alan

 

Hmm... mine has PS so maybe that's why it's positioned up. I suppose it might be to keep the wires away from the PS belt??

 

Hi sck,
I read it to be just the opposite … on bb, p/s cars the plug is down?
But????
Could it be the rear case is 'clocked' incorrectly on the front case?
Regards,
Alan

Here's a 69 SB with the plug in what I would call the 'up' position.

 

From the January, 1969 Chevrolet Service News...

Ed

 

Hi Ed,
I still don't understand.
If I'm looking at the drawing correctly the alternator had been installed with the 'plug' that sck1 is talking about at the 6:00 position. Then the end frame was re-clocked so the 'plug' in question was at the 9:00 position.
Is that so? Was the alternator still to be considered installed up-side down? Was the stamped information on the case still on the underside of the alternator?
Regards,
Alan

 

You are correct regarding the plug (old - 6:00 / new - 9:00), and the reason is because of the way the alternator adjusts on 427's with power steering (up and down instead of the "normal" left and right for non-power steering cars - see below), the BAT (battery) power connector (which was originally located about an inch away from the valve cover!) could hit the valve cover if you weren't careful when replacing the belt. All they did was to clock the rear of the alternator housing 90 degrees counter clockwise so it moved the BAT connector farther toward the driver's side fender and away from the valve cover. The front of the alternator (the mounting points) stayed the same.

Since the numbers are stamped on the front housing, they didn't move and yes, they face the ground, so you need a mirror to see them.

You'll notice that my alternator doesn't have the correct "heat fins". That's because I refuse to pay stupid prices for the "correct" one. However, the idea is the same...

Ed

 

Hi Ed,
Now I think I understand!
And of course the picture with notes is worth at least 10,000 words!
Thanks!
Regards,
Alan

 

Restoman's picture is showing the same "clock" position as my 69. With the support on the harness. The wires to the plug will break over time and with the vibrations. Broken wire= no charge. And just because it can, it will be the small "excite" wire that breaks first.

 

Remember though, the change didn't occur until the late October, November or early December, 1968 time frame.

It's first mentioned in the January, 1969 Chevrolet Service News, and typically it took them one or two months from first draft to publication and distribution, so cars assembled before this time period will still have the old alternator configuration (unless the dealer made the change). Exactly when the change took place on the assembly line is impossible to know since these records aren't available. The AIM is of no use since it doesn't mention anything about it, but even if it did, the revision dates in the AIM don't necessarily reflect the date the change was actually made. It only indicates when the drafting room released that particular sheet, which was created as a result of an engineer submitting an ECR (Engineering Change Request) to Drafting. The change could have actually been implimented a few months before, or a few months after any date you see in the AIM.

Ed

 

This is GREAT guys!

I guess I'll have to split my alternator case to get it positioned correctly. As for that service bulletin, it's going in my resto-book just in case I need some "back-up" come judging time.


Thanks Again,
Sum