1970 SB w/AC. Do I have the Correct Fan Clutch & Fan?

[Clark E.]

I've owned this car since 1972. The drive train is original. It has a 5 blade fan. Jim Prince's 1968-72 Restoration Guide indicates some '70 SB's with A/C have a 5 blade fan w/ blades that have a greater pitch that those used on non-A/C cars. There isn't a part # on the fan. On on side the fan hub is stamped with an "H" (August?) the word "FRONT" and a "99". The other side has a "W" on one of the brackets holding a blade. One of the blades is stamped with a "6" or a "9" (not sure which).

The fan clutch hub is dated 1 17 69 followed by what I believe is "SC" which is for the mfgr. Schwitzer Corporation according to the JM.

I believe these parts are original and correct but the information on the fan doesn't correlate and the cluch hub date is more than a year earlier than the block casting date and build date of the car (3/21/1970).
Appreciate assistance determining if these parts correct or something else? Thanks...Clark Erlandson

[David L.]

Re: 1970 SB w/AC. Do I have the Correct Fan Clutch & Fan?

Clark,

Your fan stamped "66" (not "99"), made by Hayes-Albion ("H" = Hayes Albion, 5 blades, 17 1/2" dia. with 2 1/4" pitch) is GM # 3888366 and is correct for 66-67 Corvettes w/427 and 68-70 Corvettes wo/ AC. According to my 1970 Corvette AIM (UPC C60, sheet C1) and my 1972 Corvette Parts Catalog (Sept. 1971) the 70 Corvette 350 w/AC used fan # 3955182 (17 1/2" dia., 7 blades). The 71-72 Corvette 350 w/AC used the 3991417 fan.

It seems to me that your fan clutch (dated 1/17/69) and "66" fan MIGHT have been original equipment on a 69 Corvette 350 without AC.
According to my 1969 Corvette AIM the 3955182 7-blade fan was used with AC (see UPC C60, sheet C2).

I believe that the 3955182 fan was made by Schwitzer and has the GM part number, Schwitzer part number (914166), and a date code stamped on it.

There is currently a 3955182 fan dated "L78" (November 1978) for sale on Ebay (not me) for 5 bills, a lot of money for an "over the counter" fan. As far as I know this fan was only used in 1969 and 1970 on Corvettes w/AC. I'm NOT sure if it was used on BB engines.

BTW, your original "66" fan is quite valuable.

Dave

http://www.ebay.com/itm/1966-69-CORVETTE-427-AIR-CONDITION-7-BLADE-FAN-3955182-66-67-68-390HP-400HP-AC-/170850781319?pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr&hash=item27c7800887

[Dick W.]

Re: 1970 SB w/AC. Do I have the Correct Fan Clutch & Fan?

Ralphie strikes again!!!!

[David L.]

Re: 1970 SB w/AC. Do I have the Correct Fan Clutch & Fan?

That fan must have been on a 1969 or 1970 Corvettes w/AC made in August 1984. Did they make 1969 or 1970 Corvettes in 1984??????
Dave

[Ralph S.]

Re: 1970 SB w/AC. Do I have the Correct Fan Clutch & Fan?

I did buy it right around that time at a local Chevrolet dealer. It is just taking up space on a shelf in my basement now.

[Clark E.]

Re: 1970 SB w/AC. Do I have the Correct Fan Clutch & Fan?

Thanks Dave, Dick and Ralph for your comments. It's evident I have a non A/C fan given the data provided. Having owned this car for over 40 years, it's difficult to assume this fan was switched out before I purchased it. Richard Prince's book indicates in two places there is evidence that a 5 blade fan was installed at the factory on a "minority" of A/C small blocks but its blades were pitched at a more severe angle than the standard 5 blade fan. Any experience with this second fan and how do I (duh!) measure blade pitch? Thanks again...Clark

[Joe L.]

Re: 1970 SB w/AC. Do I have the Correct Fan Clutch & Fan?

Thanks Dave, Dick and Ralph for your comments. It's evident I have a non A/C fan given the data provided. Having owned this car for over 40 years, it's difficult to assume this fan was switched out before I purchased it. Richard Prince's book indicates in two places there is evidence that a 5 blade fan was installed at the factory on a "minority" of A/C small blocks but its blades were pitched at a more severe angle than the standard 5 blade fan. Any experience with this second fan and how do I (duh!) measure blade pitch? Thanks again...Clark

Clark------

I agree with you. I just do not understand how this fan could have wound up on this car post-factory during the first few years of its life. It's not impossible but it just seems highly unlikely to me.

As far as blade pitch is concerned, you don't need to measure it. The 5 blade fan you have has the greater blade pitch. In fact, it's the only 5 blade fan ever originally used on 68-70 Corvettes and the stampings on yours indicate this is the fan you have. The lesser-blade-pitch 5 blade fan was used on some pre-1968 Corvettes but its markings are different than the one you have.

[Clark E.]

Re: 1970 SB w/AC. Do I have the Correct Fan Clutch & Fan?

Thanks Joe...Always appreciate your insight. The fan clutch is dated 1 17 69, some 14 months before the car was assembled in March, 1970. The engine cast date is early January, 1970 which is OK but I'm somewhat miffed by the 12 - 14 months the clutch date preceeds these dates. Have you experienced this much of a time difference with other cars?...Clark

[Joe L.]

Re: 1970 SB w/AC. Do I have the Correct Fan Clutch & Fan?

Thanks Joe...Always appreciate your insight. The fan clutch is dated 1 17 69, some 14 months before the car was assembled in March, 1970. The engine cast date is early January, 1970 which is OK but I'm somewhat miffed by the 12 - 14 months the clutch date preceeds these dates. Have you experienced this much of a time difference with other cars?...Clark

Clark-----


It's highly unusual but in rare cases it could occur. It could involve something like salvaged parts from the repair area being returned to the assembly line.

Another possibility: These 5 blade fan assemblies do not include a date. So, the only real date you have is the one on the fan clutch. It's possible that the clutch was replaced under warranty very early in the car's life and the replacing unit was taken from dealer stock with an "old" date. That still leaves the question of why the 5 blade fan on a C-60 car but, for 1970, I think it's possible

[David L.]

Re: 1970 SB w/AC. Do I have the Correct Fan Clutch & Fan?

Clark,

To measure the pitch simply place the fan on a flat table and measure the vertical height from the table to the highest point on any one of the blades. The pitch of the 3888366 fan should measure about 2 1/4".

To calculate the angle "A" just use some simple high school math.
The true width of the blade is 4.00".
sin A = 2.25"/4.00" = 0.563+/-
A = 34.3+/- degrees

Noland Adam's 1963-1967 restoration book shows a shop drawing of the 38883266 fan on page 415 (you will need a magnifying glass).
The true width of the blade is shown as 4.00".
The pitch angle is shown as 34 degrees 30 minutes +/- 1 degree (in other words, 33.5 degrees to 35.5 degrees)
H = 4.00" X sin 34.5 = 2.27"+/- (close enough to 2 1/4")

Dave

[Clark E.]

Re: 1970 SB w/AC. Do I have the Correct Fan Clutch & Fan?

Thanks Dave...Believe I done broke the code! My readings range from 2 1/8" to 2 1/4" depending on which blade is measured.

What's the consensus on how the fan clutch (early 1969 date) and 5 blade fan will be evaluated during judging given the history of the car?...Clark

[Graeme B.]

Re: 1970 SB w/AC. Do I have the Correct Fan Clutch & Fan?

Don't the '69 and '70 sw clutch hubs have different bolt spacings.
Cheers, Graeme.

[John H.]

Re: 1970 SB w/AC. Do I have the Correct Fan Clutch & Fan?

Don't the '69 and '70 sw clutch hubs have different bolt spacings.
Cheers, Graeme.

Graeme -

As I recall, that changed in 1971, along with the shaft pilot diameter and the fan-to-clutch bolt pattern.

[Terry M.]

Re: 1970 SB w/AC. Do I have the Correct Fan Clutch & Fan?

Graeme -

As I recall, that changed in 1971, along with the shaft pilot diameter and the fan-to-clutch bolt pattern.

You have that right John.

[Clark E.]

Re: 1970 SB w/AC. Do I have the Correct Fan Clutch & Fan?

Guys...I hate to reopen a 6 year old post regarding the correct fan for my 1970 350/300 with C-60 but having lost points during a recent chapter judging decided to continue researching the issue of 5 rather than 7 blade fans on some C60 equipped 1970's. Page C1 of Section C60 indicates the correct part # is 1966990 which hadn't appeared in the earlier responses. The fan in the drawing on C1 is exactly like to fan on my engine with 3 blades close together, a space and then 2 additional blades close together. Unfortunately and as previously noted, there isn't a part number on the fan nor is there one on the fan clutch.

I'd appreciate knowing what the parts manuals indicate about the application of part #1966990. Thanks...Clark