69 BB Corvette Outer Alternator Bracket; Is AIM Wrong

[Jack O.]

Hi everyone,

I'm looking at the alternator installation in my '69 AIM page J427, N40 option, and it clearly shows the "outer" alternator bracket, #15 I believe, attaching to the waterpump stud with a lock washer and nut - same place my AIR pump bracket attaches. However It will not reach and I've found some pictures showing that bracket instead attaching to the block where the upper bracket is attached. Paragon catalog shows it this way too. Is the AIM incorrect?

I'm using the original brackets I took off and even have an extra one that also does not reach. I've pulled the alternator several times in the past so didn't bother taking a picture of how it was installed but it just does not seem possible to mount in the manner illustrated in the AIM.

Thanks,

Jack

[Joe L.]

Re: 69 BB Corvette Outer Alternator Bracket; Is AIM Wrong

Hi everyone,

I'm looking at the alternator installation in my '69 AIM page J427, N40 option, and it clearly shows the "outer" alternator bracket, #15 I believe, attaching to the waterpump stud with a lock washer and nut - same place my AIR pump bracket attaches. However It will not reach and I've found some pictures showing that bracket instead attaching to the block where the upper bracket is attached. Paragon catalog shows it this way too. Is the AIM incorrect?

I'm using the original brackets I took off and even have an extra one that also does not reach. I've pulled the alternator several times in the past so didn't bother taking a picture of how it was installed but it just does not seem possible to mount in the manner illustrated in the AIM.

Thanks,

Jack

Jack------


The brace, GM #3955180, attaches between the alternator bracket outboard attaching point and the waterpump left side upper stud. The AIR pump brace, GM #3921903, also attaches to the same waterpump stud. I do not know why yours does not fit assuming you have the correct parts.

[Jack O.]

Re: 69 BB Corvette Outer Alternator Bracket; Is AIM Wrong

Apparently in '68 it was attached to the upper bracket inner bolt (see 68 AIM image). My 69 AIM shows a change to the bracket part # in Sept '68 and the drawing was revised in Nov '68 (see second AIM image) so perhaps the bracket was changed to the waterpump stud at one of those points. Still doesn't explain my issue since I have a Jan '69 car so perhaps I do just have an incorrect bracket. What's really baffling though is I have an old picture and although it's not perfectly clear it sure does look like that bracket goes down to the waterpump stud.

I'd be curious if other 68-69 BB with PS owners could let me know the configuration of their bracket.

Thanks,

Jack

[Edward B.]

Re: 69 BB Corvette Outer Alternator Bracket; Is AIM Wrong

Jack, I don't know if this will help, but here's my October 21st build 1969 L36 with N40.

Ed

[Joe L.]

Re: 69 BB Corvette Outer Alternator Bracket; Is AIM Wrong

Apparently in '68 it was attached to the upper bracket inner bolt (see 68 AIM image). My 69 AIM shows a change to the bracket part # in Sept '68 and the drawing was revised in Nov '68 (see second AIM image) so perhaps the bracket was changed to the waterpump stud at one of those points. Still doesn't explain my issue since I have a Jan '69 car so perhaps I do just have an incorrect bracket. What's really baffling though is I have an old picture and although it's not perfectly clear it sure does look like that bracket goes down to the waterpump stud.

I'd be curious if other 68-69 BB with PS owners could let me know the configuration of their bracket.

Thanks,

Jack

Jack------


Yes, with respect to the upper support, there was a change from 1966-68 and 1969+. It's also very possible that late 1968 used the 69+ configuration and components OR that early 1969 used the 66-68 configuration and components.

Basically, the 1966-74 configuration is the same with the exception of the upper support. The 1966-68 configuration used upper support GM #3878239. This support attached to the inboard and outboard holes of the alternator bracket, GM #3878236 ( over the lower support at the outboard hole). I've NEVER understood what purpose or value the upper support added to the assembly in this configuration.

For 1969 the configuration of the assembly was changed and a new upper support introduced, GM #3955180. This support mounted between the outboard hole of the 3878236 alternator bracket and the upper left stud on the waterpump. In this configuration, the support adds strength to the alternator mounting.

For 1971 things changed again but only slightly. The GM #3955180 upper support was replaced by the GM #3986109. The latter support installed exactly like the 3955180 and was interchangeable with the 3955180. In fact, in 1972 the 3986109 replaced the 3955180 for SERVICE. Because of a difference in length, the 3878239 is not interchangeable with the 3955180/3986109, at least not interchangeable as far as how installed.

In your situation it's all about the upper support. If you have the support that installs between the inboard and outboard holes of the alternator bracket, then you have the 1966-68 configuration. If you have the support that installs between the outboard bracket hole and the upper left waterpump stud, then you have the 1969-74 configuration. If you consider that the upper support you have is original to the car, then your 1969 was built with the 1966-68 configuration, which, as I mentioned, is very possible for an earlier build 1969.

[Edward B.]

Re: 69 BB Corvette Outer Alternator Bracket; Is AIM Wrong

I always thought this setup was hokey from the start!! Too many brackets going all over the place! My 68 Camaro L89 also has N40 and A.I.R., and it uses a completely different setup. MUCH better than the big block Corvettes! I've always wondered why the Corvette big blocks had to use a different setup than the Camaro, Nova, Chevelle, etc... unless it had something to do with the hood clearances on the Corvette.

Ed

[Joe L.]

Re: 69 BB Corvette Outer Alternator Bracket; Is AIM Wrong

I always thought this setup was hokey from the start!! Too many brackets going all over the place! My 68 Camaro L89 also has N40 and A.I.R., and it uses a completely different setup. MUCH better than the big block Corvettes! I've always wondered why the Corvette big blocks had to use a different setup than the Camaro, Nova, Chevelle, etc... unless it had something to do with the hood clearances on the Corvette.

Ed

Ed------


Camaros use a different type of power steering system. Also, while 1967-68 Camaros with V-8 used the short leg waterpumps like all Corvettes, 1969 and later Camaro V-8 used long-leg style waterpumps.

[Jack O.]

Re: 69 BB Corvette Outer Alternator Bracket; Is AIM Wrong

Thanks Ed. Yours is as expected and matches the 69 AIM. As Joe said, could just be my car ended up with the previous brace either on the line or in the many years after that but what baffles me is a pic from previous owner right before I bought (back) the car showing it attached to the waterpump stud and it seems impossible to get it configured in that way. Should of taken my own picture before I took it apart - oh well. I also owned this car for a year in 1988 but I sure don't remember the alternator brace details and have no old pics of the engine bay - regrettably.

[Jack O.]

Re: 69 BB Corvette Outer Alternator Bracket; Is AIM Wrong

The main complaint I have is it's very difficult to check the PS fluid. Another reason I fixed my PS fluid leaks. It's also a PIA getting the PS pump back on and tensioning the belt.

[Jack O.]

Re: 69 BB Corvette Outer Alternator Bracket; Is AIM Wrong

Thanks for the details Joe!

[Jack O.]

Re: 69 BB Corvette Outer Alternator Bracket; Is AIM Wrong

Ed, I'd appreciate it if you could also upload a pic of the backside of the Alt showing the wiring harness connections and also how the temp sending unit wire is routed if yours is still fairly correct.

The only weirdness I have is on the 2 prong connector, which has a red and a brown wire, the red wire is about 2 inches or so longer coming out of the harness which serves no purpose since they both go into the same connector. Just doesn't look right. Also, I have a clip on my left valve cover which I believe is for the temp sending wire but not sure how its routed from the harness.

Thanks,

Jack

[Joe L.]

Re: 69 BB Corvette Outer Alternator Bracket; Is AIM Wrong

The main complaint I have is it's very difficult to check the PS fluid. Another reason I fixed my PS fluid leaks. It's also a PIA getting the PS pump back on and tensioning the belt.

Jack------


Both of your difficulties are widely shared and will exist whether the car has the 66-68 or 69-74 configuration.

If you wish, you can convert to the 1969-74 configuration simply by changing the upper support. Everything else remains the same. One word of caution, though: I have found that many "reproduction" brackets, braces, and supports of all sorts are "off" with respect to conformance to original specs usually resulting in difficulty or impossibility of installation. One of the most notorious is the1968-74 AIR pump bracket, GM #3919890. While they might appear OK, some of these out there are so far "off" it's impossible to install them.

[Edward B.]

Re: 69 BB Corvette Outer Alternator Bracket; Is AIM Wrong

Ed, I'd appreciate it if you could also upload a pic of the backside of the Alt showing the wiring harness connections and also how the temp sending unit wire is routed if yours is still fairly correct.

I believe the alternator harness has been repaired at some point because of the electrical tape and tie wraps. I'm not sure about the temperature sender wire. It DOES have the cloth covering, but it DOESN'T look to be 50 years old!

Also note that the spark plug wires are NOT correct, but I don't "show" the car. It's a "driver" so they're from Auto Zone.

Ed

[Joe L.]

Re: 69 BB Corvette Outer Alternator Bracket; Is AIM Wrong

I believe the alternator harness has been repaired at some point because of the electrical tape and tie wraps. I'm not sure about the temperature sender wire. It DOES have the cloth covering, but it DOESN'T look to be 50 years old!

Also note that the spark plug wires are NOT correct, but I don't "show" the car. It's a "driver" so they're from Auto Zone.

Ed

Ed------


The wire looks to be a lighter green than the original wire. In any event, the connector and temp sender are not correct. 1968-71 used a pin type sender. This is a button type sender.

[Jack O.]

Re: 69 BB Corvette Outer Alternator Bracket; Is AIM Wrong

Thanks Ed. I may post a request after searching first, seems like something I'm sure other folks have asked about. I know the original pin connector on the sender has popped up as the replacement, which you have, shows up a lot. You can get a "repair" wire with the wrapping like you have but with the correct connector and the correct temp sending unit which is what I did and mine also is a lighter green.