1966 big block radiator fan. How to I.D.

[Mark F.]

Hello All. Got tired of my L72 getting to warm for my liking in Houston summer heat, so decided to give the cooling system a thorough going over. Had the original copper-brass radiator re-cored, correct water pump by chevy cool and correct clutch for the fan rebuilt.

Now I am looking at the Fan blade assembly. My current fan has a "H" and a single "6" and a "FRONT" stamped on the front of it and the "W" on the back. I am having trouble making sure I got the correct fan, so I have some questions.

1) According to the 1966 judging guide. The diameter is suppose to be 17.5 inches, (small block 17 1/8"). With the asymmetric blades this is not easy to measure accurately, fan blades are exactly the same size, However the fan pitch for the big block is a 2' pitch and the small block is 1 5/8" pitch. Is there an easy way to measure this pitch to make sure I have the correct fan?

2) Again, according to the judging guide the big block fan 'May'

[Russ T.]

Re: 1966 big block radiator fan. How to I.D.

Mark,

It looks to me like the correct fan for a 1966-1969 427/450 HP car, although there isn't a part number stamping on it.

I am sending a fairly descriptive E-bay link from the late John Greenhoe for a similar fan:

https://www.ebay.com/itm/403869122040

There is a slight dent in one of the blades which has the number "27" stamped in it. ???

Hope this helps.

Russ Trotter
NCRS #15044

[Stephen L.]

Re: 1966 big block radiator fan. How to I.D.

Photos of my 1967 427/390 no AC fan. April build date.

[Mark F.]

Re: 1966 big block radiator fan. How to I.D.

Hey Russ. Thanks for the reply. Just looked at the link and I guess that listing ended a while ago. I determined it was a big block fan by the pitch and diameter. Thank You for the confirmation though.
It took me a while to figure out the pitch, but finally just laid it flat on the table and the trailing edge was two inches taller than the leading edge, just like the judging manual said. ( I way overthought ways to try to measure the pitch.) For the diameter I made a compass with a pin, piece of cardboard and string. The diameter was hard to figure with the asymmetrical blades and the so similar diameter of the small block fan.

As far as the stamping goes the JM says "MAY" have a 66 stamped on it while mine only has one 6. So that's when I was not sure what I had.

Thanks for your help. Putting it back together now. Thanks Mark

[Mark L.]

Re: 1966 big block radiator fan. How to I.D.

Mark, the several fans that I have owned for both 66 and 67 big blocks have a "66" stamped on them. Also Tony Stein introduced me to his homemade pitch gauge which makes it super simple to check the pitch. He may be able to give you more details.

[Mark F.]

Re: 1966 big block radiator fan. How to I.D.

Thanks Stephan. I don't have a 67 JM, but the 66 JM shows it "MAY" be stamped like yours (double 66). Mine had a single "6" stamp on it, that is when I started doing the research. They have both single 6's and double 66's stamped fans on the internet both claiming to be big block fans. I am putting mine back with my fan as is as the $750 for the double 66 fan on the internet was a little cost prohibitive and I am pretty sure my fan is a big block fan as has the diameter and I think the pitch. But I would feel a lot better if it had the double 66 stamping. Thanks for your help. Cheers. Mark

[Mark F.]

Re: 1966 big block radiator fan. How to I.D.

Thanks Mark. At the Texas Regional I saw a judge with a took for measuring the difference between the pitch. Should have asked him how it worked but at the time I did not think I would need it. I may try to talk to Tony. Thanks. Mark

[Mark M.]

Re: 1966 big block radiator fan. How to I.D.

Mark, there's an original fan here that I measured. When engine side is laid flat on a bench, the fan clutch surface is 1 1/4". The top edge of the blades measure 2 1/8". There was an article in The Restorer Magazine showing differences of many fans and if I remember correctly , on the bench measurements were used. Hope this helps.

[Mark F.]

Re: 1966 big block radiator fan. How to I.D.

Thanks Mark. When I laid the fan flat, (without clutch on) on my work bench, I did get about two inches from the bench on the bottom side of the trailing edge of the blade. The fan/clutch is back on the car now so I would measure it more accurately if I had not already installed it.

When you say the "fan clutch surface is 1 1/4" I apologize, but not sure what measurement you are referring to.

I will try to find the article in the Restorer Magazine you are talking about.

I will say the original fan clutch I got from Dave Sokolowski and had rebuilt was significantly smaller in diameter then the one that was on the car.
Hopefully this will allow more air to be pulled by the fan. It also has a little longer shaft putting the fan a little bit closer to the radiator. Hopefully this all help keep the big block a little cooler in the south Texas heat. Thanks for your help. Mark