C1 Fan Alternator Belt L48?

[Robert S.]

I'm really perplexed about the correct fan/alternator v-belt for my '78 L48 AC 4-spd. Since I want to have the car judged, I ordered a Quanta belt, D-281D GM# 9433656 .380 x 53.00. According to the JG this # should be correct. But its too short!

With the belt on the crank and water pump pully's and alternator moved fully to the center of the engine (hitting the valve cover) there's at least a half inch space between the top of the belt and the top edge of the pully it needs to go over. There is no way it will fit! It seems I need a 53.5 or 54 inch belt. I don't have a problem with the PS or AC belts - the car doesn't have an air pump.

Its been a long time since I changed this belt but I think I may have had this problem before and had to get a longer one the last time I changed it.

The alternator was changed out about 12 years ago with a service replacement, other than that the engine is original. Its a late June build if that makes a difference.

Has anyone else run into this problem? Does anyone know what the problem could be? TIA for your help, Bob

[Jack H.]

Re: C1 Fan Alternator Belt L48?

If the pulley's the belt wraps around aren't correct/original (see your copy of the Assembly Instruction Manual), then the reproduction V-belts will probably NOT fit...

[Dick W.]

Re: C1 Fan Alternator Belt L48?

The belt that the GM parts book calls for is also 53.00 inches long (9433759) The belt listed for a '79 with the same application is 54.00+ long. (9433761)
I would call Quanta and explain your dilemma.

[Joe L.]

Re: C1 Fan Alternator Belt L48?

Bob------

The belt shown by Quanta is the GM part numbered belt that was supposed to have been used in PRODUCTION. The length of that belt is, indeed, 53.0". I see a few possibilities here:

1) The belt specified as the PRODUCTION belt was not the one actually used. I have seen this before with PRODUCTION belts. In general, the problem I've found with the PRODUCTION-specified belts is that they are too short. So, my general observation is consistent with your experience;

2) As Jack mentions, a pulley or pullies may have been changed at some point. This is highly unlikely for the waterpump and crank pullies. Besides, the "with C-60" waterpump pulley used for your application is the largest OD pulley ever available from GM that would fit a 1978 Corvette waterpump. However, the biggest possibility for a pulley change would involve the alternator. It may be that the rebuilt alternator that was installed was supplied with pulley and, if that's the case, it might not be the correct pulley. Do you know that the pulley on your alternator is the original pulley?

[Robert S.]

Re: C1 Fan Alternator Belt L48?

Thanks Jack, Dick, Joe, for your replies.

Jack, I am the original owner and I am confident the crank and WP pulleys are originals and the AC and PS belts are fine. But as Joe questioned the replacement alternator pulley is not.

Dick, that is what I was thinking since this is a June 30 build car. I see there is a listing for a first and a second design for the 79 alternator belts. My GM parts book also lists an aluminum bracket and a cast alternator bracket. I have a cast bracket with the numbers 3951337 on it.

Joe, good question about the alternator pulley. The one on the car has a OD of 2 5/8" on the front flange. Do you know if this is the correct size?

Thanks and all,
Bob

[Joe L.]

Re: C1 Fan Alternator Belt L48?

Bob-----

The original alternator pulley for your application was GM #1949355. The "official" GM spec for OD on this pulley is 2-1/2". However, the pulley actually measures 2-5/8", so you have the correct one. In fact, this is one of, if not the, smallest OD alternator pullies ever used on a Corvette.

1972 through 1978 Corvettes generally used the GM #3951337 cast iron alternator bracket. This changed for the 1979 model year and the GM #14015510 cast aluminum bracket was used 79-82.

1978 and 1979 both used the same PRODUCTION alternator belt for L-48 with C-60 applications, that belt being the 53.0" GM #9433656. Late 1979 L-48 with C-60 did use a different alternator belt and that belt was a 54.0" belt of GM #9433658 (SERVICE GM #9433761). However, late 1979 with C-60 also used a different alternator and different alternator pulley. This late alternator was a 70 amp unit of of Delco series 15SI. Other lower-rated alternators were series 10SI. The series 15SI has a larger diameter. It also uses pulley GM #14015512. I have no specs, at all, for this pulley.

I am pretty sure that the change to the aluminum alternator bracket was done to accomodate the use of the series 15SI alternator on some 1979+ models. The aluminum bracket can accomodate both the series 10SI and the series 15SI. However, I believe that the earlier cast iron bracket can accomodate only the series 10SI for some reason or another.

So, after all that, we still can't figure out why the 9433656 belt won't work.

[Wayne P.]

Re: C1 Fan Alternator Belt L48?

You may be able to install it by loosing the water pump pulley or the alternator bracket. I have done this several times on C3 belts that appeared too short because they would not easily go over the pullys.

[Joe L.]

Re: C1 Fan Alternator Belt L48?

Bob-----

Wayne brings up a good point. It is sometimes necessary to remove/loosen things beyond what's necessary to just stretch a belt over the alternator pulley.

One other thing that I've been think about, though: what is the alternator that is currently on the car? Is it a 10SI or might it be a 15SI? A 10 SI can be most easily identified by the fact that the split ring case half (i.e. the rear case half) has cast-in "ribs" around the complete circumference of the rear half of the side of the case half. The 15SI does not have this. Also, what is the part number and amp rating stamped on the drive-end case half?

[Robert S.]

Re: C1 Fan Alternator Belt L48?

Joe,

The amount of information you have is amazing. Thanks for confirming the pulley and bracket. I just checked and its a 10SI - its got a full rack of ribs! Sorry for the food reference, I must have food on my mind since I haven't had dinner yet

As near as I can tell the part number is 1102401 37A - the 2 could be an 8 and the last 0 could be a 9 - with 5K15 12V NEG below. It was a FLAP exchange. There no other stamps or labels left or readable on the unit.

I doubt its really a 37A, since I've never had a problem with it keeping the battery charged even after running the AC or the rear defogger.

I think I might be left with Wayne's suggestion or a BFH But how when I replace it with correct # and dated one, I'll know exactly what to look for

Thanks again for your assistance and education,
Bob

[Robert S.]

Re: C1 Fan Alternator Belt L48?

Thanks for the suggestion Wayne

Bob

[Joe L.]

Re: C1 Fan Alternator Belt L48?

Bob------

I think that it's probably 1102481. This is a 37 amp, 10SI unit originally installed on 1975-76 Pontiacs and Oldsmobiles. Given the date code, I'd say it was likley originally installed on an early 1976.

In any event, the original application has no meaning, whatsoever, in the case of an alternator that's been through a commercial rebuilding operation---they don't rebuild individual units. They completely disassemble alternator cores, inventory the pieces, and use the pieces to build up rebuilt units. It's the same way that the alternators were originally built up by Delco-Remy except that the commercial rebuilders use mostly used, reconditioned parts rather than all new parts. The 37A rating means nothing, either. That's just what the original case half was used for. The same case half can be used for any SI series alternator up to 63 amps.