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Hello All - I know the alternator bracket for 396's is different than the 427, but can you describe how? Also can you tell me the part number for this? I have seen NOS parts with a number and without. Which is correct for judging? The judging manual makes no reference to a part #.
Part # is 3863138, does not appear on the part. Other casting marks that are there: outboard, between the two alternator bolt eyelets, a large triangle with a capital E enclosed. Below that, on the web of the rib, almost halfway towards the lower headbolt mount hole, the letters G.M. Now, rearwards from that, on the web below the horizontal rib, towards the rearmost head mount, the number 2 (believe this is the mould #, as I have another almost mint example with "1"). Flip the bracket over, almost opposite the mould # is a circle with the letter G within. All these markings are embossed(?) (deeper than surrounding metal).
Now the major 5-foot identifier, and where it mostly differs from the '66 non-PS bracket, is the outer rib. On the L78, it goes straight back, on '66s, the rearmost rib is raised almost a quarter of an inch above the forward rib, then, to get the arm back to the rearmost mounting bolt, droops down to the eyelet. I think this was for more clearance around the exhaust outlet (for headers, etc.).
The JM & TG says nothing about all these identifiers.
doesn't the idler belt on the 396 utuilize the front grooves on the water pump and harmonic balancer pullys whereas the 66 up big block idler belts were on the rear grooves? mike
I believe the only difference between the 65 and 66 alt mounting brackets would be the bend on the rear leg that Wayne Midkiff described. The bend was necessary to clear the new for 1966 A.I.R. system pipes that screwed into the exhaust manifold. The leg of the new design bent up and around that area instead of passing directly over it. There may have been other changes also but I'm not aware of any.
Yes, that's another difference for '66-up #3883810
The '65 L78 bracket measures 7.0" from the center of the rear bolthole to the front face of the alternator mount (where the long bolt head would contact). I would imagine that the same dimension on the'66-up non-PS lower alt. brkt. would be 3/4" greater, to place the alternator belt in the outer groove of the crank and water pump pulleys. I seem to remember that the casting # of the 810 is somewhere on the bracket.
I just replaced the alternator bracket on my '66 L-72 427 which I did believe was wrong for the car. (Alt. belt on 1st track pully, closest to engine side) which is not correct for a '66. I purchase the correct brkt. from GM for the '66-74 BB, w/o PS. The old brkt. I took off is the same as described by Wayne. It's for sale if you want it and I can e-mail you a picture, just e-mail me.
Ken / Kurt -- there's another '66-up bracket (identified by the raised rear horizontal arm that droops to the bolt hole) of the (otherwise) same dimensions as the L78 bracket. I have one that I picked up at a swap meet. This puts the alternator belt in groove # 1, just like '65 396, but of course the arm configuration is wrong for an original L78 bracket. I'm guessing that it might have been used in 1966-up BB passenger cars with a single water pump groove pulley (ie. no w/p idler belt). Works fine for a poor-boy '65, though.
i got a repo casting for one of my 396's years ago from Barry Blocker of manchester, ill. he may have some left . they were excellent duplicates of originals. don't have barry's #. good luck, mike
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