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Discussion Starter · #1 ·
I have a friend with a SBC in a 49 Olds that has had two alternators fail within 2 years. The alternators are part of a March Front Drive system and are mounted with the back of the alternator almost against the front of the cylinder head. There is no bearing housing sticking out the back. When the first one went out, the only one in the state of Ohio was at Jeg's in Columbus. We drove from Cincinnati to get the replacement for $350+ and now a little over a year later it has failed. Anyone else having issues?? Any solutions??
 

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Why not run some "stick on" firewall heat tape between the head and the back of the alternator case?

If not that why not a simple piece of aluminum mounted between 2 bolts (so it is not hitting the head or the alternator) on the studs attaching the alternator to the head to serve as a heat shield?
 

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Discussion Starter · #5 ·
Took the first failed alternator apart. Turns out the problem is the front bearing. It is not a sealed bearing and it was pretty chewed up, luckily it did not affect the stator or rotor. The rear bearing was fine and is a sealed bearing. Was thought it was the problem because of location next to head, but no evidence of heat issues. Bought new bearings and replaced them both with sealed bearings. Will tear the replacement one apart to see if it has the same issue. FYI these alternators are Tuff Stuff alternators. Belt tension is low if anything, but yes it is not a self adjusting tensioner.
 

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Is the alternator out further then the next two pulleys?

Making the belt slightly crooked and wear on that bearing uneven?
This could be fixed with spacers on the other pulleys.


Is the alternator pulley a overdrive pulley giving a different ratio then stock?

If your crank is say 6 and alternator 2.375 then that gives a 2.53/1 ratio. If you put a 1.875 pulley in place of the 2.53 pulley then that increases the ratio to 3.20. If you have a high reving engine then the alternator that would be turning 15,180 rpm at 6000 rpm with the 2.53 ratio will now be turning 19,200 at the same 6000 rpm.
 

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I think you've encountered the " cheap junk imported bearing" zone doesn't seem to matter who's name is on the part , there's a lot of sub par crap being sold these days ..FWIW most all gm frt alternator bearings weren't sealed , IME. They only had a shield on one side ..
 

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Discussion Starter · #8 ·
Finally got the second alternator torn apart. Turned out to have a cracked brush holder. Rest of it was fine. Replaced brush holder and all tested good. The old Oldsmobile now has a spare alternator and the one on the car just made it from Cincinnati to Biloxi for Cruisin-the-Coast.
 
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