63 360 HP fan clutch

[Troy P.]

Which of these two are the correct fan clutch for my 63? In case neither is 100% correct which is the most correct, the newer looking one or the older appearing one I've been using?

If you need more detailed photos to tell I'd be happy to provide them.

Thanks in advance for sharing your judging expertise.

[Mike M.]

Re: 63 360 HP fan clutch

the step in the shaft of the gold cad plated clutch makes it a service replacement. the uniform OD of the used clutch is similar, if not identical to that of an original 63 but go to the 65,66 0r 67 judging manual where the lengths of the shafts of a BBC vs SBC is discussed. i can't tell for sure from your photos but the used one appears to have the BBC length. mike

[Troy P.]

Re: 63 360 HP fan clutch

Thanks Mike. I have the 63-64 judging guide but not the later one you suggest.

The shaft length of the one I've been using is 1 3/8" and the flange is 3/16".

[Joe L.]

Re: 63 360 HP fan clutch

the step in the shaft of the gold cad plated clutch makes it a service replacement. the uniform OD of the used clutch is similar, if not identical to that of an original 63 but go to the 65,66 0r 67 judging manual where the lengths of the shafts of a BBC vs SBC is discussed. i can't tell for sure from your photos but the used one appears to have the BBC length. mike

Mike and Troy-------


The new fan clutch pictured is a GM #3916141 or reproduction thereof. That fan clutch was originally used on some 1968 big blocks and continued to be used through 1969 for some big blocks. It has a shaft length originally intended for big blocks. However, over the years all of the other 1960-70 Corvette fan clutches were discontinued and replaced by the 3916141 for SERVICE. So, while the 3916141 does SERVICE all 1960-70 small blocks, it does not actually have the same shaft length as original small block fan clutches.

The fan clutch on the right could be a GM #3814560 or 3814137 originally used for all 1963 Corvette applications. It definitely has the small block shaft length.

By the way, GM did away with the different fan clutch shaft lengths after 1970 for both PRODUCTION and SERVICE. So, 1971-74 big blocks and small blocks used the same fan clutches although several different variations were used over the period.

[David L.]

Re: 63 360 HP fan clutch

According to my notes the measurement from the fan mounting surface to the water pump hub mounting surface is 1.8" for the 327 fan clutches and 1.4" for the 427 fan clutches.

Dave

[Troy P.]

Re: 63 360 HP fan clutch

Since my shaft is 1 3/8" (1.375" or roughly the 1.4" you mention) this would be for a big block per your notes. But Joe says it is the small block shaft length. So I'm confused.

It is the fan clutch that came on my '63 when I bought it. But of course I can't say if it is the original factory installed part as it may have been replaced over the years.

[Mike M.]

Re: 63 360 HP fan clutch

the 65,66 and 67 judging manuals give the specs on the clutch's shaft dimensions. mike

[Joe L.]

Re: 63 360 HP fan clutch

Since my shaft is 1 3/8" (1.375" or roughly the 1.4" you mention) this would be for a big block per your notes. But Joe says it is the small block shaft length. So I'm confused.

It is the fan clutch that came on my '63 when I bought it. But of course I can't say if it is the original factory installed part as it may have been replaced over the years.

Troy------


Your existing fan clutch is definitely the small block fan clutch. In fact, you can clearly see the difference in lengths in your photo. The 3916141 is seen with the shorter shaft (since the 3916141 was originally a big block fan clutch) and your original clutch is seen with a longer shaft.That's exactly the difference between the small block and big block fan clutches.

[David L.]

Re: 63 360 HP fan clutch

Since my shaft is 1 3/8" (1.375" or roughly the 1.4" you mention) this would be for a big block per your notes. But Joe says it is the small block shaft length. So I'm confused.

It is the fan clutch that came on my '63 when I bought it. But of course I can't say if it is the original factory installed part as it may have been replaced over the years.

Troy,

Over the past 35 years I have owned many 6" dia. fan clutches similar to your vintage fan clutch. Most of them were identical to yours with many teeth around the perimeter and 2 "flat" areas (about 1/2" long or so) and at the 12 o'clock and 6 o'clock positions. However, I also once owned a fan clutch that was similar but had 4 "flat" areas at the 12 o'clock, 3 o'clock, 6 o'click, and 9 o'clock positions around the perimeter. I suspect that this fan clutch with the 4 "flat" areas was an early version used from 1960 to maybe 1963 or so.

Dave

[Richard G.]

Re: 63 360 HP fan clutch

Below are pictures of the clutch removed from my 1963 340HP. I don't know for sure if it is original to the car.


It sure appears similar to the older on pictured above. I have not been able to decode the L7C ink stamp.

[David L.]

Re: 63 360 HP fan clutch

Richard,

L7C =November 7, 1962

The fan clutch appears to be original for your 1963 assuming the date code checks out.

I had a similar fan clutch dated "L27G" (November 27, 1966) that came with a 5-blade Schwitzer fan dated "L6" (November 1966).

Refer to the link below.

Dave

showthread.php

[Richard G.]

Re: 63 360 HP fan clutch

thanks Dave.
My car has a build data of December 21 1962. Looks like it likely came on the car.
My odometer was at 80K but was broken when I purchased the car. I does have the original metallic pads still on the brakes.
My best guess is around 100K miles. Zero miles in the last 29 years. This will change soon.
Rick