5-Blade Fan need help dating

[Rob H.]

Hey there - I acquired a 5-blade fan under the impression that it was the correct application for my '69 427 (L36) non-AC car. Could someone with fan expertise please let me know what I've got here - any info would be greatly appreciated!

Here is some info and some measurements to help: It has "H" and "FRONT" written on it (it does not have the "66"). The hole is 2 3/8". The circumference is approximately 17.5" (tough to be exact due to the way the blades are splayed out). And the distance from the center of the bolt hole to the hole diagonally across from it is 3".

Thanks in advance for any help!

Rob

[Jack H.]

Re: 5-Blade Fan need help dating

You can get a better measurement of the fan's diameter this way:

Lay it on a piece of blank paper. Strike two lines joining the fan to fan clutch mounting holes across the center hole. Where the lines intersect, that's the center of the fan assy.

Now, measure from the center to the tip of each blade and double the measurement to derrive diameter from your radius measurement. Add the five figures and divide by five to average your measurements. Each fan blade is not necessarily the same length as the others mounted on the fan assy's center spider...

Trying to measure tip to tip across a five blade fan is tricky and it's pretty easy to wind up with an uncertainty factor of 1/4"...

You're trying to verify the fan in question is a bona fide GM 3770529 rated as a 17-1/8" diameter. There was an early and a late version of the part with the distinction being the geometry of the rivet heads used to attach the blade to the spider (early = mushroom; late = flat or 'button' shaped). Your copy of the applicable judging guide book tells you which configuration to look for in terms of model year.

Also, be aware the equivalent 5-blade fan used on Chevy passenger cars of the era is ALMOST IDENTICAL with the difference being its diameter was greater (both 17-1/2" and 18" fans were used in passenger car applications of the era).

On dating, you will not find 5-blade fans to be routinely dated. On 7-blade fans, almost all were dated AND bear the GM PN on one or more of their blades.

[Grant W.]

Re: 5-Blade Fan need help dating

Hi Rob
You have a correct fan blade for a 68 s/b vette with A/C It is also a replacement fan second design for 66 and 67 s/b vette with A/C. This fan is also used on a 68 Camaro with A/C

Part number 3789562.

I went through years of this collection process of these fan blades thinking it was for a B/B only to find out with many discussions with Joe L that it was a small block A/C fan blade. You need the H and 66 for your L36.

Hope this helps.
Grant

[David L.]

Re: 5-Blade Fan need help dating

It's a piece of cake to measure these fans. The hub hole is 2 3/8" in diameter. Half of that is 1 3/16". Place a measuring device with the 1 3/16" mark on the edge of the hub hole and the other end along the center line of one of the blades. The zero end of the measuring device is now at the center of the 2 3/8" hub hole. The other end tells you the radius. It should be one of the following: 8 1/2", 8 9/16", 8 3/4", or 9".

To measure the pitch simply place the fan on a flat table and measure the VERTICAL HEIGHT of one of the blades.

The following are all 5-blade Hayes-Albion fans with the "H" stamping:

The 65 Corvette 395 fan (GM # 3872792) will have a pitch of about 2 1/8" with the radius at 8 1/2" (17" dia).

The 66-67 Corvette 427 & 68-70 Corvette 350/427 fan will have a 2 1/4" pitch with a radius of 8 3/4" (17 1/2" da.) as well as the "66" stamping.

The 66-67 Chevrolet & Corvette 327 w/AC fan (GM #3789562) will have a pitch of about 1 5/8" with a radius of 9" (18" dia.) and 4 rivets per blade.

The 58-63 Chevrolet 283/327 w/AC fan (GM #3749576) is almost the same as the 3789562 fan EXCEPT it has 5 rivets/blade and was replaced with the 3789562 fan in July 1964 as per Chevrolet Parts History.

The very COMMON 60-67 Corvette fan (GM # 3770529) will have a pitch of about 1 5/8" and radius of 8 9/16" (17 1/8" dia.) with 5 rivets per blade. The 1960-1964 or so fans have "dome headed" rivets while 1965-1967 or so fans have "flat headed' rivets. The rivet type changed sometime in 1964, I believe.

The 66-67 Corvette 327 w/AC also used a 5-blade Schwitzer fan, 18" dia. with 912239 (the Schwitzer part number) and a date code stamped on the blade.

Rob,
I disagree with Grant. I believe your fan is GM # 3749576 (58-63 Chev. V8 w/AC) if it measures as an 18" fan. Measure it and we will find out. The 3789562 was 4 rivets/blade.
I still have about 40 or 50 fans in my "collection" but no longer any 66-67 427 & 68-70 350/427 fans stamped "66".

Dave

[Wayne M.]

Re: 5-Blade Fan need help dating

....The very COMMON 60-67 Corvette fan (GM # 3770529) will have a pitch of about 1 5/8" and radius of 8 9/16" (17 1/8" dia.) with 5 rivets per blade. The 1960-1964 or so fans have "dome headed" rivets while 1965-1967 or so fans have "flat headed' rivets. The rivet type changed sometime in 1964, I believe. ....

Here's a pic of a '529', and yes, it is approx. 1_5/8" pitch. Mushroom head rivets, as it's probably off a '64 or '65 (the 2 possible cars from which the owner donated his excess parts ). Per '65 TIM&JG, the round head rivets were TFP, except for the L78.

[Rob H.]

Re: 5-Blade Fan need help dating

First off thanks very much for everyone's feedback...

Per David's nifty measuring technique, the length of the blades from the center of the hole measure 8 3/4" (or 17.5" in total diameter). The rivet heads (5 per blade) are flat, and the pitch is 2 1/4"...



Rob

[David L.]

Re: 5-Blade Fan need help dating

First off thanks very much for everyone's feedback...

Per David's nifty measuring technique, the length of the blades from the center of the hole measure 8 3/4" (or 17.5" in total diameter). The rivet heads (5 per blade) are flat, and the pitch is 2 1/4"...



Rob

Rob,

Your fan appears to be GM # 3888366 except it is missing the "66" stamping but it does have the "H" and the "FRONT" stampings. The hub hole is 2 3/8". The bolt circle is 3". The radius is 8 3/4" (17 1/2" dia.). The pitch is 2 1/4". Is the length of each blade 5.93" (or about 5 15/16")? Is the measurement from the bottom end of the blade to the first single rivet 1.44" (about 1 7/16")? Refer to Noland Adams 63-67 restoration book, page 415 & 426. Are you absolutely sure that the measurement from the CENTER of the hub hole to the tip of a blade is 8 3/4"? If so, I think you have the correct fan. It's possible that you might have an "early" 3888366 fan that did not get the "66" stamping or there was a mistake and the fan did not get stamped "66".

The only other 17.5" 5-blade fan that I know of is the one used on 71-79 Corvettes wo/AC (GM # 3991420) but it has a 2 5/8" hub hole, a 3.25" bolt circle, 5 rivets/blade, and I believe only a 1 5/8" pitch.

Dave