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#1
05-04-2019, 07:55 AM
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Alternator Belt, looking for correct fit
I've shopped locally for an alternator belt but the belts I've bought are either too long or too short. The alternator brackets are original.
I see one in the OPGI magazine for $53.00. This seems like crazy money for a belt when locally I've spent $12.00. Any suggestions such such as a part number through Summit Racing or Napa or common auto supply chains through out the states? 67 GTO, Auto, PS, no AC
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1967 GTO, hard top, 400 Block, Butler Performance Build, EFI Holley Sniper, Tremec 5-Speed, Moser 373 Rear, 4 Wheel Disc Brakes |
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#2
05-04-2019, 08:08 AM
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I'm also looking at the National Parts Deport magazine and they are showing 4 belts listed as 1st, 2nd, 3rd and 4th qtr. I called them for support and they sound as clueless as I am.
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1967 GTO, hard top, 400 Block, Butler Performance Build, EFI Holley Sniper, Tremec 5-Speed, Moser 373 Rear, 4 Wheel Disc Brakes |
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#3
05-04-2019, 10:02 AM
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Be advised that there are different width belts used.
Parts people do not know this anymore. That's what causes the screech. Mine is an AC car, NAPA Premium XL #25-7495 on alternator, NAPA Premium XL #25-13453/7530 on PS. Last edited by Old Goat 67; 05-04-2019 at 10:12 AM. |
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#4
05-04-2019, 11:09 AM
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Belt width is real important, but IMO nothing promotes belt slippage like a shiny groove. In that respect, that chrome pulley isn't doing you any favors. IIRC, 66s didn't use the wider belt, so should one get added to the mix...
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#5
05-04-2019, 05:05 PM
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Quote:
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1967 GTO, hard top, 400 Block, Butler Performance Build, EFI Holley Sniper, Tremec 5-Speed, Moser 373 Rear, 4 Wheel Disc Brakes |
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#6
05-04-2019, 05:40 PM
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No, that's a third belt.
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#7
05-04-2019, 08:34 PM
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Gates #7495 for fan and Alternator, # 7512 for fan and power steering.
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Remember no one is perfect. Everyone's butt has a crack in it! |
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#8
05-07-2019, 06:16 PM
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I picked up part #25-7495 from Napa today; it's clearly too long., I have a Butler Performance built engine, maybe they put on a smaller pulley on the crank. Anyway, back to the auto parts store tomorrow
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1967 GTO, hard top, 400 Block, Butler Performance Build, EFI Holley Sniper, Tremec 5-Speed, Moser 373 Rear, 4 Wheel Disc Brakes |
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#9
05-07-2019, 07:47 PM
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something I see is ..
thats not a factory tin alternator pulley.. in your picture looks like a solid repro or a buick one .. its diameter is probably different than original also making the correct belt not fit along with the other pulley diameter differences you mention may have happened ... are your crank and water pump pulleys tin or aluminum ?? pictures ?? part numbers ?? |
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#10
05-08-2019, 05:19 PM
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Finally, Napa XL 25-7475 seems to be a great fit.
As for belt tension; should I pull the alternator back with one hand and tighten the bolt with the other or should I use a pry bar to make it really tight?
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1967 GTO, hard top, 400 Block, Butler Performance Build, EFI Holley Sniper, Tremec 5-Speed, Moser 373 Rear, 4 Wheel Disc Brakes |
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#11
05-08-2019, 05:49 PM
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Hard to say just how tight it needs to be. Too tight is hard on alternators. Too loose causes slippage. Look at the longest straight section of belt, at about the midpoint and see how much slack there is. I'm guessing an inch of flex (total) should be close?
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#12
05-09-2019, 10:47 PM
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Agreed. Hand tight will almost certainly cause it to squeal with any kind of electrical load draw or RPM. Too much pulling with a pry bar is too hard on the alternator bearings.
The sweet spot lies in-between. 
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Eric Mitten '74 Bonneville 4dr Sedan (455/TH400/2.93 open) '72 LeMans GT (455/M-13/3.23 [8.5"] posi) '71 GTO Hardtop (400/TH400/3.07 12 bolt posi) ‘71 GTO Convertible (455HO/TH400/3.23 posi) '67 GTO Coupe (455/ST-10/2.93 posi) Deuteronomy 8:3 
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#13
05-10-2019, 03:31 AM
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In the middle of the belt, you should be able to give it a 1/4 twist (turning the bottom sideways) with your hand. No more, no less, that should be perfect.
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1969 Pontiac Firebird |
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#14
05-11-2019, 09:33 PM
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I was always told to have 1/2" of play in the belt. 1" is too tight, and tightened by hand is too loose. And that was by professional mechanics back in the 60s. Back then they knew how to do things the right way.
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 Gary Get in, ShuT Up, Hang On! Member of the Baltimore Built Brotherhood MY GTO built 4th Week of March 1966 "Crusin' Is Not A Crime" Keep yer stick on the ice. |
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