Hi guys long time no see. I am back in another 93 and working on getting the kinks out of it.What happens is when I mash the pedal once it hits ~ 5krpm my electrical voltage drops.It is not as noticeable in the day time but at night with the lights on it drops to ~9V on the gage and tonight for the first time the battery indicator flashed in the DIC when it happened.

I had a Corvette forum member suggest that alternators can drop voltage due to contact lift off at high RPMs but this is ridiculous.Engine stumbles when it happens at night. I have a receipt from the previous owner of 2 rebuilds on this alternator. Maybe it is just bad. First though I am replacing the belt and tensioner. My theory on it is as the rpms ramp up the belt lifts off of the alternator pulley via centrifugal force. I need an extra belt anyway and maybe the tensioner is weak they both play a role in keeping the tension on the pulley.At lower RPMs the Volt gage reads ~14V.

I also have a weepy WP gasket I get a little oil on the hood after a good romp but nothing a quick wipe does not clean up. I am not sure if it is residual oil from the intake I re did last week. I cleaned up as best as I could but it was a mess and I see no leak there anymore. I am not sure whether a little oil being flung off the belt ( that is where it gets on the hood just above the AC and alternator) is enough to cause slippage or not.

So does anyone have any thoughts? Has anybody had this problem?

A bad alternator won't drop it to 9 volts all at once unless there's some sort of intermittent dead short occuring in the windings. The system has about 12.5 volts from the battery alone, and plenty of racers run without alternators at all.

Are you sure that oil isn't coming from the a/c compressor? I can't think of anything else that'd sling oil onto the hood.

No not sure where it is coming from but on my last car the exact same thing happened when my ex mechanic fubared the WP seal install but it was a lot more oil. Still wondering whether that will cause belt slip. I hear ya on the voltage I was suprised to see it drop that low but I am not sure how many amps the engine sucks up at 5k rpm. Battery is new and hold a good charge. It sorta acts like a 5k short but that doesn't make any sense.

How about this question? How much belt deflection should you get between the AC and Alternator? Should the tensioner be able to move and how much? I think I get around 1 1/4 inch deflection downward there and I am able to move the tensioner up 1/4 to 1/2 inch in the process. Seems to me it should be tighter in that spot.

What CC says makes sense.
First, the display shows system voltage not alternator output. If it showed alternator output, it would read 0 volts before you started the engine. It will show the battery voltage before you start and show what the alternator is putting into the system after the engine is running. Even if the alternator is cutting out, you should still see what the battery voltage on the display, like 12.2 or whatever. Even if the belts are slipping, you'll see battery voltage.
Hook a voltmeter directly to the battery posts, key on, are the voltmeter and display readings the same? Start the car, check the readings. Take it to hi RPM and check.
If you have to do this while driving, hook 2 wires to the battery and run them thru the window to a voltmeter.
Sounds to me like a bad ground under vibration, loose plates in the new battery (possible but not likely) or something in the wiring.
I think the LT1 would run fuel pump, injectors and computers without dropping to 9v. Like CC said, some racecars run without alternators. We can run an injected car for 3, 1/2 hour race sessions without charging the battery and that's with a battery that measures 6 x 6 in. and 4 in. high, very small.

If your WP seal is leaking, you should see oil on the front of the oilpan.

I would say that the voltage drop at high rpms, in addition to the engine stumble, makes me wonder if there isn't something wrong in the coil... it's drawing too many volts and still can't draw enough.

Just a stab.

That thought enter my mind too but here is what I found today.I went and did some more testing. I used the analog gage last night ( I know better DUH) but today I used the digital. With lights off it drops to 12.2V from ~14.2V with lights on it drops to 11.8V. I did notice the battery reading 11.5V before start up with the key on. So I guess it rules the ground out. Seems a little low on the battery to start and I am leaning more towards the belt/ alternator as the cause.

Where does the wire feeding the voltage guage come from?

I'd look on that end of the circuit. Maybe it's also feeding the coil. Or maybe the coil is crapping its pants over 5,000 rpm and that's pulling down the voltage on that circuit.

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Start with the basics!!!! A battery reading of 11.5 volts on a vehicle that has recently been driven is bad...

I would first start with the battery connections...make sure they are clean & tight......I see more batteries etc being replaced because of bad connections than bad batteries
...not sure how you ruled the ground out???

Then test the battery and alternator..

My point is fix the problem you have before you start the car, i.e. the 11.5 volt battery, then worry about the 5000 rpm problem if it is still there..

Good luck..

I agree I am thinking 11.5 after 24hrs is not a good thing. I see the previous owner used a channel lock on the positive cable rounded it so I am going to replace the lug and take a good hard look at the battery. Might be time for a replacement. It should read over 12V correct?

If it isn't holding 12.6V or higher then it needs to be retired and replaced.

10-4 was going to measure it tomorrow and get a quality replacement while I wait for the tensioner and belt to get here. I will be glad when I get to the end of this refurb on this car. Always something else popping up but I should be done with it all by June. Most of the mechanical stuff is nearing an end (except for the freakin heater core that just started leaking).Still got some cosmetics left. Did a new Partsladi console today. No Dulso but it looks like it and I am pleased. I was able to buy a GM NOS door bezel and am going to save that part for the final crowning. Still have to send the radio off to Dr. Don replace the chime ( I got one waiting) and have a new rear Bumper that is the correct color waiting for pick up. Mine has a bulge above and below the third light as well as 2 tone paint they re painted the top and the bottom looks like crap. My new bumper is 90% perfect and needs a little spot touched up. I will be bored soon enough but then the opti will probably bite it....

Put the new battery in got 12.5 V now and got an added benefit. I mentioned sending my Bose out. It did not read the stations right nor allow me to set any of them. The CA In light was on all the time so I figured the switch was stuck inside. Since the battery replacement IT WORKS PERFECT. It even reads CDRs. Happy day I saved $200 and did not even have to change to Progressive or Gieco.

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A fully charged battery will be over 13v. But there's some drain overnite.
I've had my C4 for 4 years, don't know how old the battery was when I bought it.
After 24 hours, for the last 4 years, everytime before I start the car, the battery reads 11.5. Doesn't bother me a bit.

Did the new battery solve the problem?

I don't think it was the battery per se but the process of taking it out and replacing it must have reset the fault that the radio had just like it resets other things when the battery is disconnected. Just a nice suprise and something to remember for others when the Bose goes.

I meant to say did it fix the voltage drop at high rpm issue? Nice to hear you saved a bunch of money on the Bose though.