1963 Alternator Questions

[Richard W.]

I have a couple of alternator questions regarding my 1963 SWC driver. I had my alternator tested today when I replaced the battery. It passed in that it put out, I believe, 14.6 amps but the test indicated a bad diode pattern. The store did not appear to know what that means and suggested not replacing the alternator since the output so high. Should the alternator be replaced? If it matters, the existing alternator code is 1100834 37A.

Also, while I have you. I noticed that the specs call for a 37 amp unit for the car (324/340 w/o air). Mid-America shows a Delco unit with 55 amps for a 1963/64 Vette. Is there any downside for using a 55 amp alternator? What about something bigger?

Thanks in advance your response.

[David Van Weele]

Re: 1963 Alternator Questions

I just checked my orginal altenator and it is 1100628-37A. I bought my car new and never replaced the alternator, it was built late May 1963 and has the 360 HP engine. The 37A is a 37amp unit which is correct for your car. I appears that your unit is putting out less than half of what it should. There are a few people that rebuild them an even date code the diodes with the correct date. I do not recall the people but I do know that they advertise with the NCRS.


My '63 Z 06

[Wayne C.]

Re: 1963 Alternator Questions

Any alternator rebuilder can replace the diodes. I know I've seen rebuild kits at parts suppliers, in fact J.C. Whitney offers rebuild kits that include diodes (http://www.jcwhitney.com) for $16. Check your phone book for local rebuilders, just make sure they understand you want your original alternator back!

[Jim Cear]

Re: 1963 Alternator Questions

Rich , I just bought an alternator for my 63 from John Pirkle in Georgia..do not have his info with me however I know he advertizes in Vette Vues mag. Mine is restored externally and internally with the correct diodes and dates. Can't say how well it works yet as it is still in the box. Good Luck!

[Duke W.]

Re: 1963 Alternator Questions

Since you don't currently have the original alternator and it's a driver, you would probably do no harm by swapping it for another rebuilt unit, however, you can buy the diodes (Borg Warner brand from Pep boys, for example) and replace them youself. The only tough part is getting the pulley nut off, which you should do anyway, especially if you still have the OEM pulley. An impact is best for that, but you might be able to get a local tire store to do it. With an impact taking the nut off takes five seconds, and about the same to reinstall it. You might also be able to get the nut loosened with the alternator installed and the belt real tight.(Have a helper sqeaeeze the belt together to get as much tension and friction as you can.)

While you have it apart, check that the bearings spin smoothly, and you should do the stator and rotor continuity checks outlined in the manual to be sure everything else is okay.

Using a larger output Delcotron will do no harm and is a typical upgrade if people install additional electrical accessories. The C60 '63s had a 52 amp unit from the factory, but I think this was a different model with a larger frame. Often the difference in rating is just a matter of the units having different stator coils. The higher amp units have more stator windings to provide additional current output.

One trick when installing an underdrive pulley is to upgrade to a higher output stator so the unit provides enough juice at idle, while enjoying the benefit of less parasitic load at high revs and longer alternator bearing life.

BTW your L-76 already has an "underdrive pulley" from the factory if it is original. It's steel or CI and measures about 3.62 inches OD. The L-76 and L-84 engines had a lower numerical drive ratio than the base and L-75s, to keep alternator speed reasonable at high revs. Because these engines idled at nearly double the speed of the base and L-75 engines, alternator output at idle is sufficient to carry the load.

Duke

[Gary Cederman]

Re: 1963 Alternator Questions

Duke, great response (as usual).

Richard, to answer your question about the 'bad diode pattern'. I do not know what that statement means with respect to an open or shorted diode but, the diodes are used to rectify the ac signal to a dc signal. It is hard to describe without a picture. But, if you know about 3-phase AC in your home Think about if you lose one of the phases. Yes, you could still measure a voltage at the outlet (much lower than what is needed) but it would be incorrect and will cause problems if not fixed. Forget what they told you at the store. You should get it fixed.

[Wayne W.]

Re: 1963 Alternator Questions

I imagine he ment 14.6 Volts instead of Amps. And ahh not many homes have three phase service, but I understand what you mean. The diodes can be easily tested.a

[Dick Kindl]

Re: 1963 Alternator Questions

Richard, I recently did a body-off resto and sent my original alternbator to John Pirkle (www.johnpirkle.com) in Augusta, Georgia for a rebuild. It came back w/new dated diodes and looked like new and worked great. John has an ad in all the Driveline mags. I also bought a correct starter dated, etc and was very satisfied. Good luck , Dick