Fan clutch unit

[Rainer S.]

What is the correct marking on the (4) bolts, which mount the fan clutch to the waterpump shaft. Since there are (3) possible choices, as per Paragon: WB,S or TR. Which is correct for an early 63 SWC Fuelie ? Also, who can rebuild a clutch unit. Mine needs it...

Rainer

[Joe C.]

Re: Fan clutch unit

Far as I know, the fan clutch was held to the pump shaft with nuts through studs. The best lead I can give you for a fan clutch rebuild is Fred Oliva. Use the following link:

http://www.gate.net/~foliva

Good luck,
Joe

[Joe L.]

Re: Fan clutch unit

Joe-----

Not for 1963. Until mid-1969, fan clutches were retained to the waterpump hub by bolts. In mid-1969 this changed to studs and that practice continued thereafter.

Fred Oliva is the guy for fan clutch restoration. In fact, I think he's the ONLY guy for such work.

[Joe C.]

Here Is What The TIM&JG Says......

.......for 1965. If there is any difference for 1963, someone please chime in.

"The fan blade assembly is attached to four black oxide integral studs on the clutch body with four hex nuts and split-type lock washers. The use of bolts to attach the fan blade to the clutch is incorrect. The clutch is attached to the water pump and pulley with 4 Cadmium or Zinc plated hex-head bolts with split-type lock washers............................."

[Joe L.]

Re: Here Is What The TIM&JG Says......

Joe-----

We're talking about two different things here. The passage that you reference relates to the attachment of the fan blade to the clutch. What I was referring to, and I believe what Rainer was inquiring about, was the attachment of the fan clutch to the waterpump.

All fan clutches used by GM had integral studs which, in combination with nuts and washers, served to attach the fan clutch to the fan. Some aftermarket-type fan clutches use threaded holes in the fan clutch body assembly in combination with bolts to attach the fan clutch to the fan. I believe the point that the judging guide is trying to make is that if you see a fan attached to the fan clutch with bolts, then the clutch is not original. That's absolutely correct, too.

The attachment of the fan clutch to the waterpump hub is another matter. Here, Corvettes used 5/16-28 bolts from 1960 through mid-1969. In mid-1969, the attachment methodology changed to studs and nuts. The studs are 5/16-28 on the end which threads into the water pump hub and 5/16-18" on the nut end.

Also, just to add an additional point, all ORIGINAL Corvette fan clutches used HOLES in the flange which attaches to the waterpump and NOT SLOTS. SLOTS were never used for original Corvette fan clutches. This is an aftermarket configuration designed to allow one part number to service multiple bolt circle mounting configurations.

[Joe L.]

Addendum

Also, I forgot to mention, the last sentence of the passage says exactly what I've been saying about the attachment of the fan clutch to the waterpump. This was the attachment configuration for 1960 through mid-1969 Corvettes, big block, small block and, probably, even medium blocks if they had built any.

[Timothy B.]

Re: Fan clutch unit

Rainer,

The four bolts that attach my fan clutch to water pump are TR headmarkings and 5/16 fine thread grade eight. Not sure of the length but I can double check if you like. Car is also a early 63 coupe.

Hope this helps you out, Tim

[Rainer S.]

Re: Fan clutch unit

Thanks everybody. Thats the info I was looking for. Tim, the size is 5/16-24 X 3/4 long. No need to double check.

Rainer