I have a 1968 327 and recently converted to a Holley Sniper EFI. The system works well but the electric fuel pump is a power hog. If I have any of the AC, windshield wipers, headlights, etc on at idle the car will stall as the voltage drops below 12.6 volts. I'm looking into changing the stock 61 amp alternator/regulator to a 150 amp internally regulated unit. The mechanic that will do this feels there are no issues. My questions are is the stock wiring adequate for this change and how about the amp meter in the gauge cluster.?

 

Are you sure that is what is causing the stalling?
What rpm are you using for idle speed and are you setting it with the AC on?

 

CS130, 100 amp... I was never satisfied with 100 amp CI alternator after switching to electric fans. Just not enough juice at idle, but the CS130 works great with slow driving, hot days and AC on.

 

I believe that if a larger alternator is installed, the wire from the alternator to the battery should also be upgraded probably to an AWG 2. Wouldn't be a bad idea to upgrade the ground also.

Paul

 

TALLEY1968....STOP! Unfortunately the alternator is NOT the issue or the answer, but the way it is wired IS an issue. The solution is NOT using a larger gauge wire necessarily either. The secret to more power in both charging and starting systems is...using relays. Do yourself a huge favor and call this guy Mark, the owner. He IS extremely knowledgeable about the early corvette wiring for the starting and charging circuits and will tell you what the real issues are in relation to the wiring. He even sells a lot of stuff if you want to purchase it, but his conversations are worth the call. The down side is, you probably won't be able to get a word in edgewise, he LOVES to talk which is fine. Another issue that you "may" see with your EFI setup is power related issues with the ECM of the unit and causing some wonky issues. They are susceptible to power fluctuations with the older wiring. I think the Fi Tech system is more sensitive to the power though.

The reason GM probably on the later model C3 corvettes with ECMs went/kept the charge wire going all the way back to the battery box and going through the battery and then running a power wire over to the ECM on its own circuit that was fused was more than likely to help smooth out the alternator pulses since ECMs don't like power spikes/ripples that much. Anyway, give this guy a call and be ready for INFORMATION overload once the conversation starts. Post up what he tells you and post whether you think he knows what he is talking about. Good luck.
MAD Enterprises

 

If your running a v belt i suggest a 100 amp unit or less. Besides EFI what else aftermarket have you installed?

 

YES- you need a new alternator and wiring

When these cars were built-

GM did NOT spend any more than they had to - especially on the electrical system. They went with smaller wires and juiced up the voltage to compensate.

Buccaneer touched on MAD electronics- here's his story on how GM cheaped out-

http://www.madelectrical.com/electri...evymain1.shtml

"If cars would have been entirely built using all minimum engineering recommendations for copper cable gauge sizes, then these cars would be hauling around a few hundred pounds of very expensive copper cable. Since it was not practical to install so much heavy copper cable on the millions of cars built, Chevy engineering provided a practical exception to the rule."

However - I think he is exaggerating on the couple hundred- maybe 25-40lbs?

Second- when these cars were designed - no way did the engineers remotely think of 1000W stereo systems- electric fuel pumps, fans and ECUs. By now they were thinking everybody would be in flying cars!!!

Yes - the way the car is wired you have dirty power- However you can use the battery to not only start the car but stabilize the voltage and clean up the AC ripple in the Electronics- they LIKE that.

The alternator rated at 60A- unfortunately that's "OGD"- or "on a good day" and at 70º-AND the engine running at 1500-1800 RPM. At idle- hot day- maybe 30A or so- designed 50 + years ago...

So more important then the alternators FULL output- you need to buy an alternator with a good rating at Idle.

The wires- unless you have replaced them- are 50+ years old (corrosion /brittle insulation) AND too small. Not a great combo.

Here's a simple straight forward way to wire up a Corvette AND it has been taken into account when you re-rout wires you can possible wire around the fusible links -which is NOT a good thing.

The Ammeter- unfortunately will probable not read correctly- as it is based on the original smaller wires and the resulting voltage drop.

You can get a replacement Voltmeter- just a disclosure- for a car that's really all you need ...that's what millions of new cars use....

I'd recommend wiring the ECU and the fuel pump DIRECTLY to the battery then FUSE there.

 

Do you have a drawing for "twin alternators" from O Rielly's?

 

Will this suffice?

 

FWIW, my stock alternator couldn't even keep up with high-beams. Knowing I was going to add more electric components, I went with a 3-wire 150A 12SI Powermaster alternator. It does fine with the dual electric fan setup I added later. My wiring is very similar to what @Richard454 shows in post 7.

Is your mechanic suggesting a 1-wire alternator because of the external voltage regulator in your 68?

 

Just go with a 140-amp CS-144. They're abundant and a lot better alternator than the 12SI.

See here: https://www.corvetteforum.com/forums...post1601740211