69 fan to clutch bolts

[Stanley S.]

Does anyone know what the correct headmark, length, and finish should be for the bolts to attach the fan to my SC clutch. Thanks. Stan

[Edward J.]

Re: 69 fan to clutch bolts

Stan, I believe that the fan clutch had studs on them.

[Stanley S.]

Re: 69 fan to clutch bolts

Edward,

The SC clutch I just bought on e-bay dated 7-16-69 has no studs, only threads to accept a bolt. I've seen pictures of other mid to late 69 clutches the same way. Have the studs been removed? Thanks.

Stan

[Edward J.]

Re: 69 fan to clutch bolts

Stan, maybe someone else will chime in, I cannot be 100% sure as I know that most of the fan clutchs I have seen have studs. I know some of the later years did go to bolts to retainer fan to clutch. And my 72 sm. block has studs.

[Bill L.]

Re: 69 fan to clutch bolts

My 70 has an "A" headmark with three lines for Grade 5 bolt.

1/2" head fine thread with an overall length of 3/4" including the head. Threads are 1/2" long.

Hope that helps.

Bill

[Stanley S.]

Re: 69 fan to clutch bolts

Bill,

Thanks. Do you know how they are plated?

Stan

[Bill L.]

Re: 69 fan to clutch bolts

Looks to me like they were gray/black phosphate.

Bill

[Bill C.]

Re: 69 fan to clutch bolts

My 70 has an "A" headmark with three lines for Grade 5 bolt.

1/2" head fine thread with an overall length of 3/4" including the head. Threads are 1/2" long.

Hope that helps.

Bill

The "A" headmark is what I see, phospated, 1/2" long

[Joe L.]

Re: 69 fan to clutch bolts

Edward,

The SC clutch I just bought on e-bay dated 7-16-69 has no studs, only threads to accept a bolt. I've seen pictures of other mid to late 69 clutches the same way. Have the studs been removed? Thanks.

Stan

Stan------


It depends which 1969 clutch you're talking about-----some used studs for fan attachment and some used bolts.

[Jeffrey S.]

Re: 69 fan to clutch bolts

Early '69 used bolts. My Oct. '68 came with bolts. I will check later for headmarkings.
Jeff

[Stanley S.]

Re: 69 fan to clutch bolts

Stan------


It depends which 1969 clutch you're talking about-----some used studs for fan attachment and some used bolts.

Joe,

The clutch is a 7.25" diameter with a rectangular bimetallic strip on the front and with straight fins. It is stamped SC by the date on the flange that bolts to water pump pulleys. I was thinking this would be the correct clutch for my 69 L71 built in Oct 69.

Stan

[Chris H.]

Re: 69 fan to clutch bolts

Stanley, here's a photo from my Dec 10, 68 car.

[Joe L.]

Re: 69 fan to clutch bolts

Joe,

The clutch is a 7.25" diameter with a rectangular bimetallic strip on the front and with straight fins. It is stamped SC by the date on the flange that bolts to water pump pulleys. I was thinking this would be the correct clutch for my 69 L71 built in Oct 69.

Stan

Stan-----


Does the front of the clutch have a "dish-like" perimeter around the ribbed center section?

[Stanley S.]

Re: 69 fan to clutch bolts

Stan-----


Does the front of the clutch have a "dish-like" perimeter around the ribbed center section?

Joe,

Yes, the front has an area outside the fins that looks similar to a pie pan that extends past the fins about 1.25". I can try to post a picture tomarrow.

[Joe L.]

Re: 69 fan to clutch bolts

Joe,

Yes, the front has an area outside the fins that looks similar to a pie pan that extends past the fins about 1.25". I can try to post a picture tomarrow.

Stan------

The fan clutch is a GM #3937771 which was used on many 1968-69 big blocks. It used BOLTS to attached the fan to the clutch. Other 1969 fan clutches used on most small blocks as well as some big blocks used STUDS to attach the fan to the clutch.