SC fan clutches--why the difference

[D S.]

I am looking for a fan clutch for my early built 1970 and on eBay there are two SC fan clutches but they appear different. One appears to have a "hubcap" on the backside that the other one doesn't.

http://cgi.ebay.com/ebaymotors/_W0QQcmdZViewItemQQ_rdcZ1QQitemZ370511568584QQruZhttpQ3aQ2fQ2fshopQ2eebayQ2ecomQ3a80Q2fiQ2ehtmlQ3fQ5fnkwQ3d370511568584Q26Q5fsacatQ3d0Q26Q5fodkwQ3dhttpQ253AQ252FQ252FcgiQ2eebayQ2ecaQ252FwsQ252FeBayISAPIQ2edllQ253FViewItemQ2526itemQ253D370511568584Q2526ssPageNameQ253DSTQ26Q5fosacatQ3d0Q26Q5ftrksidQ3dp3286Q2ec0Q2em270Q2el1313Q26Q5ffviQ3d1

http://cgi.ebay.com/ebaymotors/_W0QQcmdZViewItemQQ_rdcZ1QQitemZ290590633930QQruZhttpQ3aQ2fQ2fshopQ2eebayQ2ecomQ3a80Q2fiQ2ehtmlQ3fQ5ffromQ3dR40Q26Q5ftrksidQ3dp5039Q2em570Q2el1313Q26Q5fnkwQ3d290590633930Q26Q5fsacatQ3dSeeQ2dAllQ2dCategoriesQ26Q5ffviQ3d1#ht_1317wt_941

Thanks,
Scott Sims
Texas Chapter

[David L.]

Re: SC fan clutches--why the difference

Scott,

The 6" dia. Schwitzer fan-clutches were installed on 1963-1967 Corvettes and Chevrolets. The 7 1/4" dia. Schwitzer fan-clutches were generally installed on 1969 & newer models.

The "CJ" fan-clutch (6" dia.) was NOT original equipment on 1969 and newer Corvettes. The fan-clutch listed in my Oct. 1969 Corvette Parts Catalog for 68 and 69 Corvettes is GM # 3937771 which I am 99% sure is 7 1/4" in dia. My 1972 Corvette Parts Catalog also lists GM # 3937771 for the 70 Corvette.

However, I once owned a 6" dia. NOS 3946049 Schwitzer fan-clutch (ink stamped "CI"), 3 1/4" BC, 2 1/8" W/P BC dated "1-11-69 SC" (Jan. 11, 1969) but the application was 69 Camaro w/396 and 69 Chevy II, Chevelle (8 cyl.).
It's new home is in San Francisco.

I assume that the 7 1/4" fan-clutch dated "11-17-69 SC" that is listed on Ebay has a 3" BC for the fan and a 1 5/8" BC for the w/pump but the seller does really specify. Always ask questions before bidding or buying on Ebay.

Dave

[D S.]

Re: SC fan clutches--why the difference

Scott,

The 6" dia. Schwitzer fan-clutches were installed on 1963-1967 Corvettes and Chevrolets. The 7 1/4" dia. Schwitzer fan-clutches were generally installed on 1969 & newer models.

The "CJ" fan-clutch (6" dia.) was NOT original equipment on 1969 and newer Corvettes. The fan-clutch listed in my Oct. 1969 Corvette Parts Catalog for 68 and 69 Corvettes is GM # 3937771 which I am 99% sure is 7 1/4" in dia. My 1972 Corvette Parts Catalog also lists GM # 3937771 for the 70 Corvette.

However, I once owned a 6" dia. NOS 3946049 Schwitzer fan-clutch (ink stamped "CI"), 3 1/4" BC, 2 1/8" W/P BC dated "1-11-69 SC" (Jan. 11, 1969) but the application was 69 Camaro w/396 and 69 Chevy II, Chevelle (8 cyl.).
It's new home is in San Francisco.

Dave

I have a late '71 SC fan clutch I bought for someone else and it is still sitting near me waiting to be picked up. When I saw those two on eBay I got curious as the one being sold by NCRS member John Meissinger looks like it but the other one, also listed for 1970 Corvette applications, was a bit different.
By the way....that is a nice looking '66 Corvette in the photo. I graduated from high school that year. A couple of years later my old high school buddy came by to pick me up in his '66 convertible to cruise around. That did it for me although I do own a C-3 and not a C-2. Yet.
The first Corvette I actually saw in real life was a new red '62 in a tiny Texas town of 700.

[Joe L.]

Re: SC fan clutches--why the difference

I am looking for a fan clutch for my early built 1970 and on eBay there are two SC fan clutches but they appear different. One appears to have a "hubcap" on the backside that the other one doesn't.

http://cgi.ebay.com/ebaymotors/_W0QQcmdZViewItemQQ_rdcZ1QQitemZ370511568584QQruZhttpQ3aQ2fQ2fshopQ2eebayQ2ecomQ3a80Q2fiQ2ehtmlQ3fQ5fnkwQ3d370511568584Q26Q5fsacatQ3d0Q26Q5fodkwQ3dhttpQ253AQ252FQ252FcgiQ2eebayQ2ecaQ252FwsQ252FeBayISAPIQ2edllQ253FViewItemQ2526itemQ253D370511568584Q2526ssPageNameQ253DSTQ26Q5fosacatQ3d0Q26Q5ftrksidQ3dp3286Q2ec0Q2em270Q2el1313Q26Q5ffviQ3d1

http://cgi.ebay.com/ebaymotors/_W0QQcmdZViewItemQQ_rdcZ1QQitemZ290590633930QQruZhttpQ3aQ2fQ2fshopQ2eebayQ2ecomQ3a80Q2fiQ2ehtmlQ3fQ5ffromQ3dR40Q26Q5ftrksidQ3dp5039Q2em570Q2el1313Q26Q5fnkwQ3d290590633930Q26Q5fsacatQ3dSeeQ2dAllQ2dCategoriesQ26Q5ffviQ3d1#ht_1317wt_941

Thanks,
Scott Sims
Texas Chapter

Scott-----


The fan clutch seen in the first of the links you posted is a GM #3937771. This clutch was used on many 1968-70 Corvettes with big block as well as some 1969-70 Corvettes with L-46.

The second clutch you have posted a link for, the GM #3916139, was used on many 1968-70 Corvettes with small block. In fact, it's the exact clutch originally installed on my 1969 300/350. I purchased several of these over the years they were available as I had a lot of trouble with them. Somewhere in my used parts "stash" several of them still reside.

[D S.]

Re: SC fan clutches--why the difference

Thanks, Joe. This will guide me in the right direction. So many idiosyncrasies in this hobby.

[David L.]

Re: SC fan clutches--why the difference

The 6" dia. "CJ" fan clutch was also made by the Eaton company (coil type fan-clutch) as well and was used on 1967 Chevrolet models w/AC and apparently was original equipment on some 1967 Corvettes as shown in the thread below.

https://www.forums.ncrs.org/showthre...=6135#poststop

[R N.]

Re: SC fan clutches--why the difference

Great post Scott - THANKS. I too was wondering the same thing as the current 1970 Judging Guide is rather vague about fan clutches and this thread answers many questions.

Can anyone comment on the green paint and yellow paint the Judging Guide talks about on the clutch?

David - BC = "bolt center" ????

[Grant W.]

Re: SC fan clutches--why the difference

I am looking for a fan clutch for my early built 1970 and on eBay there are two SC fan clutches but they appear different. One appears to have a "hubcap" on the backside that the other one doesn't.

http://cgi.ebay.com/ebaymotors/_W0QQcmdZViewItemQQ_rdcZ1QQitemZ370511568584QQruZhttpQ3aQ2fQ2fshopQ2eebayQ2ecomQ3a80Q2fiQ2ehtmlQ3fQ5fnkwQ3d370511568584Q26Q5fsacatQ3d0Q26Q5fodkwQ3dhttpQ253AQ252FQ252FcgiQ2eebayQ2ecaQ252FwsQ252FeBayISAPIQ2edllQ253FViewItemQ2526itemQ253D370511568584Q2526ssPageNameQ253DSTQ26Q5fosacatQ3d0Q26Q5ftrksidQ3dp3286Q2ec0Q2em270Q2el1313Q26Q5ffviQ3d1

http://cgi.ebay.com/ebaymotors/_W0QQcmdZViewItemQQ_rdcZ1QQitemZ290590633930QQruZhttpQ3aQ2fQ2fshopQ2eebayQ2ecomQ3a80Q2fiQ2ehtmlQ3fQ5ffromQ3dR40Q26Q5ftrksidQ3dp5039Q2em570Q2el1313Q26Q5fnkwQ3d290590633930Q26Q5fsacatQ3dSeeQ2dAllQ2dCategoriesQ26Q5ffviQ3d1#ht_1317wt_941

Thanks,
Scott Sims
Texas Chapter

Hi Scott
The correct style for your 70 is the one John Messinger is selling. However if you you have an early 70 then the clutch flange maybe an early smaller diameter measuring 2 3/8th across. I have a 5/5 70 fan clutch and it is the same diameter as the 68 69 style. The later 70's flange maybe dated after 5/5 70 could have changed up the a 2 5/8th diameter across. Just to be sure check your original fan on your 71 if it is 2 3/8 across or 2 5/8's across..

The reason I am posting this is because a couple of years ago a fellow NCRS member was asking for an Jan or Feb 1970 fan clutch. His was missing his original but he had a 68 dated fan clutch, a small diameter and the fan he had was original to the car. Small 2 3/8 diameter hole. I only had the one dated Feb 1970 fan clutch and it fit perfectly for his car.
Hope this helps.

You may use a late 69 fan clutch if you can't find an early 70. If you need some help send me an email, I have several late 69 fan clutches.

Thanks Grant

[D S.]

Re: SC fan clutches--why the difference

Thanks, Grant. It's always nice to hear from you. I will email you on the fan clutches. Will you be at the Frisco, Texas Regional?

[R N.]

Re: SC fan clutches--why the difference

Okay guys and gals. This post got me on the hunt for a correct fan clutch for my '70 454. My engine is stamped T0123 CZU (Jan, 23rd, 1970)

I've had some help here from the membership by emails but I'm confused as to what I have and what I need. I measured my current water pump bolt centers were the fan clutch hub bolts to the water pump and I measure 1-1/4" which I have been told is correct (small hub) for an early 1970. But the bolt centers were the fan clutch bolts to the fan measures 2-1/8". Some say this should be 3" +/- Whats correct for my application?

The hole in my fan where the fan clutch goes through is approx. 2.5" or 2-5/8" dia. and a quick measurement of the fan dia. looks to be 17.25 or 17.5". I looked at some old judging sheets from a regional when my car was judged and the fan and clutch scored perfect (no deductions)

All help appriciated.

[Joe L.]

Re: SC fan clutches--why the difference

Okay guys and gals. This post got me on the hunt for a correct fan clutch for my '70 454. My engine is stamped T0123 CZU (Jan, 23rd, 1970)

I've had some help here from the membership by emails but I'm confused as to what I have and what I need. I measured my current water pump bolt centers were the fan clutch hub bolts to the water pump and I measure 1-1/4" which I have been told is correct (small hub) for an early 1970. But the bolt centers were the fan clutch bolts to the fan measures 2-1/8". Some say this should be 3" +/- Whats correct for my application?

The hole in my fan where the fan clutch goes through is approx. 2.5" or 2-5/8" dia. and a quick measurement of the fan dia. looks to be 17.25 or 17.5". I looked at some old judging sheets from a regional when my car was judged and the fan and clutch scored perfect (no deductions)

All help appriciated.

Kurt-----


The fan clutch-to-fan mounting for a 1970 should have a 3" BOLT CIRCLE (the DIAGONAL measurement between the mounting holes) The hole in the center of the fan blade should be 2-3/8". Here's how it is:

1960-70

Hub mounting= 1-3/4" bolt circle

Fan clutch-to-fan= 3" bolt circle

Fan blade center hole= 2-3/8"

1971-82

Hub mounting= 2-1/8" bolt circle

Fan clutch-to-fan= 3-1/4" bolt circle

Fan blade center hole= 2-5/8"

Some later 60's-early 70's passenger cars use hub mounting pattern the same as 1960-70 Corvette BUT fan clutch-to-hub mounting pattern same as 1971-82 Corvette. No Corvette ever used this combination, though.

[David L.]

Re: SC fan clutches--why the difference

Great post Scott - THANKS. I too was wondering the same thing as the current 1970 Judging Guide is rather vague about fan clutches and this thread answers many questions.

Can anyone comment on the green paint and yellow paint the Judging Guide talks about on the clutch?

David - BC = "bolt center" ????

Kurt,

Yes, BC = bolt circle

Dave

[R N.]

Re: SC fan clutches--why the difference

Kurt-----


The fan clutch-to-fan mounting for a 1970 should have a 3" BOLT CIRCLE (the DIAGONAL measurement between the mounting holes) The hole in the center of the fan blade should be 2-3/8". Here's how it is:

1960-70

Hub mounting= 1-3/4" bolt circle

Fan clutch-to-fan= 3" bolt circle

Fan blade center hole= 2-3/8"

1971-82

Hub mounting= 2-1/8" bolt circle

Fan clutch-to-fan= 3-1/4" bolt circle

Fan blade center hole= 2-5/8"

Some later 60's-early 70's passenger cars use hub mounting pattern the same as 1960-70 Corvette BUT fan clutch-to-hub mounting pattern same as 1971-82 Corvette. No Corvette ever used this combination, though.

Joe,

My eyes were opened when you said measured accross the "DIAGONAL"....
I had been measuring "ACROSS" L-R and not diagonal - Doh!

I re-measured everything and now all my measurements match the ones you provided with with - THANK YOU Joe!

[David L.]

Re: SC fan clutches--why the difference

Okay guys and gals. This post got me on the hunt for a correct fan clutch for my '70 454. My engine is stamped T0123 CZU (Jan, 23rd, 1970)

The hole in my fan where the fan clutch goes through is approx. 2.5" or 2-5/8" dia. and a quick measurement of the fan dia. looks to be 17.25 or 17.5". I looked at some old judging sheets from a regional when my car was judged and the fan and clutch scored perfect (no deductions)

All help appriciated.

Kurt,

Does you fan have 5 blades and the number "66" and the word "FRONT" stamped on it?

Dave

[R N.]

Re: SC fan clutches--why the difference

Kurt,

Does you fan have 5 blades and the number "66" and the word "FRONT" stamped on it?

Dave

Hi David,

YES, 5-blades. The fan is mounted on the car so I assume I can't see the word Front and the number 66. Can you see these without the taking the fan/clutch assembly off?