OK, This is a head beater.  I just installed a new HEI Tach Drive distributor in the 69.  At an idle, I have about 14 volts to the distributor.  On my way up to 3,000 RPM, the voltage flucuates between 11 and 18 volts. When I steady the rpms at 3,000 the voltage stabilizes.   Anybody have any ideas? 

What is the voltage at the alternator doing? 18v is more than a properly working alt. should put out. You may have a regulator problem there...

At the alternator the voltage stays between 14 and 15 volts.  The only problem wire is the one to the HEI.  I am baffled and so is a friend of mine that is an ASE certified Tech and has been for more than 30 years.   I installed the first HEI from Summit on Sunday.  It was doing the same thing then (with the exception that the spikes and drops were much more radical 0 to 32 volts).  I put a new regulator in the alternator just to be  on the safe side.  I had a brilliant idea, I removed the battery from the wife's 69 Camaro, sat it on the floor and ran a ground to the frame and a direct hot lead to the distrtibutor thus removing the ignition system from the cars electrical system no change in the voltage drops and spikes.  I returned the distributor to Summit on Monday and they sent me a new one.  I put it in yesterday and it didn't change much.  The highs are now at 18 and the lows are around 9 or 10.  These drops and spikes are just flashs on the volt meter.  Everything is grounded. I ran continuity tests on almost every part of the car. The dash is grounded. The block is grounded.  The frame is grounded.  Beats me.  I installed Accel armor jacketed wires.  They are properly gounded to the engine.  I just wondered if there is some kind of stray voltage signal being generated back through the jacketing that could cause the feedback.  Thoughts!!! 

Does the car run ok, or is there a miss/surge, etc?
If you are taking these voltage readings off of the single, "BATT" wire to the dist/coil, it don't make any sense at all. I can't see the coil/ign module adding voltage to that wire...that's just...odd...
Does your voltage meter have a Min/Max function? I would use one that does, and see if the readings are a bit more steady. If the car runs ok, and the only issue is with the voltage on that wire, I'd say let it run. On the other hand, if there is a problem with how the car runs/idles...

You would have to have a serious, high powered voltage source in direct contact with that wire to induce that kind of fluctuation...you don't have a microwave in that thing, do ya?
I'm at a loss here, too! I'll ponder this for a while...

Thanks.  I have been pondering this for a week.  I asked the same question over on Team Camaro.  One of the answers I got was that there is some feedback from the HEI and that I should try reading that wire with an analog volt meter.  I have never had any reason to check this before so I can't be sure what normal is.  I checked the wifes Camaro and the voltage readings seemed to be pretty steady.  The only reason I was checking this is because the car sounds like several cylinders are laying down.  The engine is a brand new GM Performance Parts long block.  All cylinders are at 150 PSI.  A friend of mine is going to check his 78 Pace Car tonight to see what readings he gets.  Even if his readings are steady it could still the difference between the GM HEI and the aftermarket piece. 

Well, I did find out some info on the flucuating voltage on the power lead to the distributor.  There is flyback voltage on the HEI that is inherent to the system.  The second thing is to use only an analog voltage meter to check that lead.  The digital reacts to any subtle change and you could burn out the diodes in the meter.  My meter still works so, I won't do that again.  As for my problems they just keep continuing.  THe Holley 670 Street Avenger that I installed had a manufacturing flaw that I was unaware of until I took it off after it was puking fuel out of the front vent tube and then cutting out while driving.  There is a batch of them that were constructed that had a problem with the base metal that did not allow the coating to adhere after exposure to fuel.  Inside the bowls and the metering plates were all blistered and flaking.  This was another contributing factor to the poor performance.  The particles were clogging the jets, boosters and the needle valves.  I called Holley and they acknowledged the problem and they are sending me a replacement carb.  I will probably sell it because I ordered a Road Demon and it should be in today.  I can not believe the series of crap that have hit me with this car and all of it has been with new parts.

That really sux...but as I always say...
"New don't mean good"...
Hope you get it all figured out, and fixed.

Well, I have the new tach drive HEI installed and a replacement carb direct from Holley.  The car runs absolutely fantastic now.  I have put 200 miles on it since I fixed the problems.  With most of the car being made up of new parts, I should be able to drive it for a few years before parts start to wear out again.  I love driving with the top down, feeling the wind across my bald head.  LOL

You have apparently already come to the proper conclusion.  If you check voltage with an older analog meter, the spikes are too small to read, but a sensitive digital will catch the normal feedback from the HEI.  That will teach you to work on an old car with modern technology tools!

I have an analog volt meter.  If I knew that the spikes were going to show so easily, I would have used it instead of the digital unit.  My most common usage for the digital meter is to check alternator output and to check circuit continuity and resistence. 1969 L462007-08-09 06:04:20