Midyear fan blades w. a/c ?

[Brandon K.]

Can someone please clear up the controversy over what the correct fan blade is for a midyear car (67) with C60? The NCRS manual specifies 5-bladed fans for all cars, both small and big block, however many cars I've seen have 7-bladed fans w. the air cond option. Is either one correct, depending upon what they had on hand the day the car was built? Does it vary depending upon engine size?

Also, does anyone know if its possible to straighten one of these fans with minor bends of the blades? How would that be done, and what about balancing? Thanks in advance. Brandon Korman

[Joe L.]

Re: Midyear fan blades w. a/c ?

Brandon----

It seems like I might have been involved in this discussion before, but, at the risk of repeating myself, I'll plunge in again.

The original fan used on 67 A/C 327 cid engined cars was GM #3789562. Optionally, fan blade assembly GM #3863137 could have been used. Although significantly different in configuration, both of these fan blades were a nominal 18" in diameter and BOTH had 5 blades.

7 blade fans were decidedly uncommon in the pre-1968 Corvette era. However, there was at least one application in which one was used. That was for the 64-65 Corvette 327 with A/C, FIRST DESIGN. That fan was GM #3853943. Some of these fans may have been still around for early 1966 production, but I doubt that any were still around for 1967 production. However, it's possible that your car is one that does and you might be able to make a case for it. Providing, of course, that yours is a 3853943. You see, there were a LOT of 7 blade fans manufactured in the post 69 era and lots of folks with marginal-cooling Corvettes retrofitted them in a futile attempt to "remedy" their cooling problems. Especially, folks with air conditioned cars.

As far as straightening a fan, I consider it risky business. Certainly not to be done without re-balancing and I'm not aware of anyone that does this for fans.

[Joe L.]

Re: Midyear fan blades w. a/c ?

Brandon----

It seems like I might have been involved in this discussion before, but, at the risk of repeating myself, I'll plunge in again.

The original fan used on 67 A/C 327 cid engined cars was GM #3789562. Optionally, fan blade assembly GM #3863137 could have been used. Although significantly different in configuration, both of these fan blades were a nominal 18" in diameter and BOTH had 5 blades.

7 blade fans were decidedly uncommon in the pre-1968 Corvette era. However, there was at least one application in which one was used. That was for the 64-65 Corvette 327 with A/C, FIRST DESIGN. That fan was GM #3853943. Some of these fans may have been still around for early 1966 production, but I doubt that any were still around for 1967 production. However, it's possible that your car is one that does and you might be able to make a case for it. Providing, of course, that yours is a 3853943. You see, there were a LOT of 7 blade fans manufactured in the post 69 era and lots of folks with marginal-cooling Corvettes retrofitted them in a futile attempt to "remedy" their cooling problems. Especially, folks with air conditioned cars.

As far as straightening a fan, I consider it risky business. Certainly not to be done without re-balancing and I'm not aware of anyone that does this for fans.

[Ray Morrison]

Re: Midyear fan blades w. a/c ?

Brandon I can only speak to 66's but I believe you will find this true for 67's as well. Originally A/C car's came equipped with both 5 and 7 blade fans. There appears to be no particular reason for which fan was installed on any particular car. HOWEVER, the A/C 5 Blade fan is NOT the same as the standard 5 blade fan. The blades on the 5-blade fan for an A/C car were turned at a different angle in order to draw a greater amount of air. While it may not seem noticable, once you see them side by side the difference in pitch is evident. Hope this helps.

[Ray Morrison]

Re: Midyear fan blades w. a/c ?

Brandon I can only speak to 66's but I believe you will find this true for 67's as well. Originally A/C car's came equipped with both 5 and 7 blade fans. There appears to be no particular reason for which fan was installed on any particular car. HOWEVER, the A/C 5 Blade fan is NOT the same as the standard 5 blade fan. The blades on the 5-blade fan for an A/C car were turned at a different angle in order to draw a greater amount of air. While it may not seem noticable, once you see them side by side the difference in pitch is evident. Hope this helps.

[Lou Lapham]

Re: Midyear fan blades w. a/c ?

Brandon-As an owner of a 66 air car i lamented the lack of a 7 blade fan when i bought my car 5 yrs ago.After reading several books on the subject i settled on Noland Adams reference in his The Complete Corvette Restoration and Techinical Guide Vol. 2 which is availible thru NCRS for a very reasonable $50.00.I would reccomend buying or borrowing a copy and read the section on fans which shows detail drawing and descriptions of the different fans used.The 7 blade is availible new from sources such as Paragon for around $200.00 but the Large 5 blade shows up at swap meets for $20 or $30 in nice shape.Many times as has been said a 7 blade is used as a last resort for better cooling.All sources don't agree but Adam's explaination is plausable.On the straigtening front i would'nt mess with a bent one as you could end up fracturing and blade and eventually throwing a blade with deadly results!! No matter which fan you end up using get a good straight one.Regards,Lou Lapham

[Lou Lapham]

Re: Midyear fan blades w. a/c ?

Brandon-As an owner of a 66 air car i lamented the lack of a 7 blade fan when i bought my car 5 yrs ago.After reading several books on the subject i settled on Noland Adams reference in his The Complete Corvette Restoration and Techinical Guide Vol. 2 which is availible thru NCRS for a very reasonable $50.00.I would reccomend buying or borrowing a copy and read the section on fans which shows detail drawing and descriptions of the different fans used.The 7 blade is availible new from sources such as Paragon for around $200.00 but the Large 5 blade shows up at swap meets for $20 or $30 in nice shape.Many times as has been said a 7 blade is used as a last resort for better cooling.All sources don't agree but Adam's explaination is plausable.On the straigtening front i would'nt mess with a bent one as you could end up fracturing and blade and eventually throwing a blade with deadly results!! No matter which fan you end up using get a good straight one.Regards,Lou Lapham

[Dennis Rosenthal]

Re: Midyear fan blades w. a/c ?

For what it's worth: My 67 L68 ac roadster has a 7 blade fan, I believe its original as it had correct dates and clutch on it. I have a very correct 66 L36 ac coupe with a 5 blade fan. There are three 67 L68 ac coupes within 10 miles of me, two have 7 blade fans and one has a 5 blade. At a recent local NCRS meeting there was a 66 300hp ac auto coupe w/a 5 blade, and 2 67 300hp ac auto coupes, both had 5 blade fans.

Dennis

[Dennis Rosenthal]

Re: Midyear fan blades w. a/c ?

For what it's worth: My 67 L68 ac roadster has a 7 blade fan, I believe its original as it had correct dates and clutch on it. I have a very correct 66 L36 ac coupe with a 5 blade fan. There are three 67 L68 ac coupes within 10 miles of me, two have 7 blade fans and one has a 5 blade. At a recent local NCRS meeting there was a 66 300hp ac auto coupe w/a 5 blade, and 2 67 300hp ac auto coupes, both had 5 blade fans.

Dennis

[Jack H.]

Re: Midyear fan blades w. a/c ?

Much has been already said about 5 v.s 7-blade fan. Proper authority should be the '67 National Team Leader -- Keith Biggers (see Driveline for correspondence particulars).

On 5-blade fans, it's NOT a happy cohesive universe. There are different part numbers for different applications and all look VERY similar except to the discriminating concours judge.

There are early and late 5-blade styles that differ in terms of blade/spyder-spoke mounting rivets (mushroom vs. button head) with the raised or 'mushroom' head rivets used in early years ('61-64) and the flatter 'button head' rivets appearing on later cars.

Next, there's an issue of passenger car vs. Corvette 5-blade fan. They look VERY similar (easy to get & cheap at swap meets in catalogs, Etc.) and will fit/substitute in a Corvette but are NOT factory concours correct.

Last, there's the issue of Corvette application. BB 5-blade fan (396) is different from SB equivalent (pitch of blade). You'll see a big jump in catalog price from correct repro BB 5-blade fan vs. non-factory original passenger car 5-blade SB fan....

So, some thing(s) to consider here in addition to 5-blade vs. 7-blade for your '67 A/C car are how concours correct do you want to be? If you're going for a top drawer restoration, there's more dot the 'i' cross the 't' detail to struggle with before acquiring a fan. ---------------------------------------------------------------

Last, you ask can fan be straightened and what about balance? Answer is yes. Like anything mechanical, achieving shape/tolerance is simply a matter of time, money, and manpower. In this era, you'll not the ABSENSE of any balancing weights on the fans. Later, on Shark cars, balancing weights appear....

Does NOT say early 5/7-blade fans were of poor/sloppy rotational inertia/balance. All blades were stamped out flat, then formed to achieve specified attack angle. Once blades were riveted to the hub/spider, balancing was achieved by milling material from the curved end of particular blade.

For grins, take a micrometer and measure the length of individual blades on known original Corvette fans. You'll find some vary from pre-formed stamping nominal length by as much as 80 mils on a given assy. This isn't the result of poor/sloppy stamping tolerance! It's how the fan was balanced -- time consuming removal of material from tip of target blade(s) to achieve what is now an unknown balance spec.

While the job can be done the problem is the recipie for what is in spec isn't in our hands....

[Jack H.]

Re: Midyear fan blades w. a/c ?

Much has been already said about 5 v.s 7-blade fan. Proper authority should be the '67 National Team Leader -- Keith Biggers (see Driveline for correspondence particulars).

On 5-blade fans, it's NOT a happy cohesive universe. There are different part numbers for different applications and all look VERY similar except to the discriminating concours judge.

There are early and late 5-blade styles that differ in terms of blade/spyder-spoke mounting rivets (mushroom vs. button head) with the raised or 'mushroom' head rivets used in early years ('61-64) and the flatter 'button head' rivets appearing on later cars.

Next, there's an issue of passenger car vs. Corvette 5-blade fan. They look VERY similar (easy to get & cheap at swap meets in catalogs, Etc.) and will fit/substitute in a Corvette but are NOT factory concours correct.

Last, there's the issue of Corvette application. BB 5-blade fan (396) is different from SB equivalent (pitch of blade). You'll see a big jump in catalog price from correct repro BB 5-blade fan vs. non-factory original passenger car 5-blade SB fan....

So, some thing(s) to consider here in addition to 5-blade vs. 7-blade for your '67 A/C car are how concours correct do you want to be? If you're going for a top drawer restoration, there's more dot the 'i' cross the 't' detail to struggle with before acquiring a fan. ---------------------------------------------------------------

Last, you ask can fan be straightened and what about balance? Answer is yes. Like anything mechanical, achieving shape/tolerance is simply a matter of time, money, and manpower. In this era, you'll not the ABSENSE of any balancing weights on the fans. Later, on Shark cars, balancing weights appear....

Does NOT say early 5/7-blade fans were of poor/sloppy rotational inertia/balance. All blades were stamped out flat, then formed to achieve specified attack angle. Once blades were riveted to the hub/spider, balancing was achieved by milling material from the curved end of particular blade.

For grins, take a micrometer and measure the length of individual blades on known original Corvette fans. You'll find some vary from pre-formed stamping nominal length by as much as 80 mils on a given assy. This isn't the result of poor/sloppy stamping tolerance! It's how the fan was balanced -- time consuming removal of material from tip of target blade(s) to achieve what is now an unknown balance spec.

While the job can be done the problem is the recipie for what is in spec isn't in our hands....