Alternator Replacement, Birkinsport

[MV8]

55 amps is marginal. The rating of alternators is normally the maximum output that can be provided intermittently and at much higher rpm than off idle. I'm sure the oem ford alt has more output off idle.

 

I don't know anything about your accessory drive, but "racing" types typically have smaller than oem crank pulleys that slow the water pump and alternator for less parasitic loss and reduced cooling and charging efficiency.

 

Also, a geo metro cooling fan should be a much lower electrical load than a good high output fan suitable for this car.

 

As long as the light is just a brief flicker, it will probably be ok but don't expect the alt to charge the battery very well/quickly if jumped off. If you upgrade lighting or the cooling fan, consider an upgrade to the alt or pulley ratio if less than oem.

Edited October 7, 2023 by MV8

[BirkinBernie]

Hi MV8 - FWIW, I have run that same alternator (though with different mounts) and a small PC680 battery for many years and have never had an issue.  Woody Harris (West Coast Birkin importer back in the 2000's) designed and sold the mounts Mark is using and provided these alternators on the new Birkins he commissioned for customers.  I think it is a pretty safe bet - at least I have never heard of any issues.

 

Happy Motoring!

[BirkinBernie]

8 hours ago, Mark Bondurant said:

Okay, more of an update!

Finally was able to take the car out for a fabulous early autumn blat yesterday and everything worked smoothly BUT...the alternator light flickers at slightly elevated RPM's. Battery is staying charged, and I have not yet checked voltage at idle or under load but am throwing it out there for any ideas. Did I get a bad alternator? Nothing else has changed. Is 55 amps enough? At least it runs, starts, and will get me through leaf season, but I'll want it fixed properly before next season. 

Thanks again all!

Mark

Hi Mark - I would monitor battery voltage and see what it looks like when the alt light flickers.  That might tell you what is going on, if anything.

[CarlB]

I have the same alternator on my car. The one I have has been modified to produce more AMPs by a company called Powermaster. Be careful about how fast the alternator spins. Check the diameter of the crank and alternator pullies and make sure you keep the alternator speed under 15,000 RPMs. My engine spins to 7500 on overspeed and I durned one up.