69 L71 fan clutch

[Graeme B.]

Hi all, I purchased a SC fan clutch but it does't fit. So ,is this the wrong one or is my fan,pulley and pump wrong?? Water pump bolt spacings is 1 3/4" .Fan is 3" spacing. Thanks,Graeme.

[Jack H.]

Re: 69 L71 fan clutch

I don't think this question can be answered until you tell us how you're measuring things: (1) hole center to adjacent hole center, or (2) hole center to hole across center...

The early shark water pump hubs and fan to fan clutch spacing was what's refered to as 'narrow' while starting in '71, the spacing went to 'large'. The hole center to adjacent hole center spacing is 2-1/8" but the hole center to hole across center spacing is right at 3".

A picture helps. Here's a BB A/C style fan clutch from the '68-68 era with 'narrow' dimensions.

[Graeme B.]

Re: 69 L71 fan clutch

Thanks Jack, I should have said Pitch Circle Diameter. Looks like I have a 70's fan clutch. Cheers,Graeme from OZ.

[Joe L.]

Re: 69 L71 fan clutch

Thanks Jack, I should have said Pitch Circle Diameter. Looks like I have a 70's fan clutch. Cheers,Graeme from OZ.

Graeme----


There are only 2 waterpump hub patterns (and, consequently, fan clutch hub patterns) used for ALL 1955-82 Corvette V-8 engines. ALL 1955-1970 used a 1-3/4" BOLT CIRCLE (measured center-to-center DIAGONALLY). ALL 1971-82 used a 2-1/8" bolt circle. As a matter of fact, this is why many AFTERMARKET fan clutches have slotted hubs; it makes for "one-size-fits-all".

As far as FAN BLADE ASSEMBLY bolt pattern, all 60-70 Corvettes with fan clutches used fans with a 3" bolt circle. All 71-82 used clutches with a 3-1/4" bolt circle. These can more easily be identified by the size of the round hole in the center. The 3" bolt circle fans have a 2-3/8" hole; the 3-1/4" bolt circle have a 2-5/8" hole.

There's one other parameter that's also important for CORVETTE fan clutches and waterpumps. 1955-70 used a 5/8" pilot on the waterpump shaft and, consequently, a 5/8" center hole in the fan clutch hub. 1971-82 used a 3/4" pilot and 3/4" center hole on the fan clutch hub. Many AFTERMARKET fan clutches will have a 3/4" center hole and include a 3/4"-to-5/8" bushing for applications requiring a 5/8" pilot.

The above applies to CORVETTE applications. Other Chevrolet applications were somewhat different in some cases. Although the hub and fan bolt patterns described above were the same for all other Chevrolet V-8 engines, some applications used different COMBINATIONS of the 2 patterns. The most common one is the "small" waterpump hub bolt circle with the "large" fan bolt circle. Although never used on a Corvette, this combination was used on other Chevrolets.

Also, most other Chevrolets used a 5/8" pilot for all years. Only Corvette and some MD/HD trucks used the 3/4" pilot for the above-referenced year range.

[Graeme B.]

Re: 69 L71 fan clutch

Thanks Joe, as you said my car came with one of those fits all size clutches with the 5/8 to 3/4" spacer. Just ordered a new Eaton. Cheers,Graeme.

[Joe L.]

Re: 69 L71 fan clutch

Thanks Joe, as you said my car came with one of those fits all size clutches with the 5/8 to 3/4" spacer. Just ordered a new Eaton. Cheers,Graeme.

Graeme-----


The Eaton is the way to go for the best combination of original configuration AND performance. For the absolute best performance, albeit at the expense of original configuration, the way to go is a conversion to a particular 71+ configuration.