My only concern with a 120 amp rebuilt Land cruiser alternator is that since they were designed for 90 amps, maybe the extra windings etc. may cause overheating issues? Is this a real concern??
My gut says "yes" this is a concern, but it might just depend on "how" it was done. The problem with low RPM high amp/ power output is the low RPM frequency. Because of "the way AC works" lower frequency AC equipment requires different magnetic design and HEAVIER transformer cores at low frequency. A great example is common 120V AC "land" equipment, vs WWII aircraft 115AC which operated at 400 cycles. The transformers and motor cores used at 400hz is MUCH smaller and lighter than 60hz
What this means in alternators is, that at lower frequency (lower RPM) the thing can NOT be as efficient and WILL cause more heating.
I don't know a definitive answer, except to hold the builder's hands to the fire so to speak. I'm with 512Strocker. If you want to be sure, and have dependable cruise, consider a larger one to start with.
