1969 cooling/radiator fan

[Joe T.]

Does a cooling/radiator fan marked
SD D72
912239
on each blade sound like a GM part number for anything?

thanks...joe

[Terry M.]

Re: 1969 cooling/radiator fan

I'll leave the number part for someone else, but conventional wisdom is that D72 = April 1972.

[Chuck S.]

Re: 1969 cooling/radiator fan

Nothing there that sounds like a GM part number, but the six digit may be a supplier's number. The D72 looks like a date code for April, 1972; if that's true, it may be a service replacement fan.

[Joe L.]

Re: 1969 cooling/radiator fan

Joe-----

I can tell you this: it's not a fan that was originally used for any 1969 Corvette application.

Check this, though: what's the bolt circle dimension of the fan-to-clutch mounting holes? Measure this as the center-to-center DIAGONAL dimension between 2 of the holes.

[Joe T.]

Re: 1969 cooling/radiator fan

Does this makes sense? This is a replacement engine, Known fact. Casting number above flywheel behind left cylinder head is 3999288 (or 289). Looks like cast date behind right head is J 5 71. Maybe this came from Chevrolet as a complete replacement engine assembly or assembled by a dealer? Still fan number does not sound like a GM part number, but if the numbers on the fan ARE dates, then the whole assembly seems to have a reasonable date correlation?

Just my curiosity and I deeply appreciate your interest,,,Regards,,,joe

[Terry M.]

Re: 1969 cooling/radiator fan

I believe, but have no proof, that the number is the number for the fan blade only, and is perhaps the fan manufacturer's internal number.
Is this a seven blade fan with the pointed tip on the blade? If so, perhaps someone reading this would be kind enough to look at their fan and report the numbers they find.

[Joe T.]

Re: 1969 cooling/radiator fan

Hi Terry:
No this is a 5 bladed fan. I am diligently hunting the correct replacement or repro fan for this motor, just as a possible replacement to put as many "original or correct" parts back on the car. Due to the engine being a replacement engine, it will never be original, but I am trying to make it original looking with no intent to deceive anyone (except maybe me?). I am just doing research to determine the possible history and pedigree. Thanks for your reponse, interest and experience...regards...joe
Also. This car had a tendecny to run on the hot side of what I consider normal, so I think a 7 blade fan will probably tend to help that as well...jt

[Mark #28455]

It shouldn't run hot

If the cooling system is in good order - radiator to shroud seals in place, front spoiler intact, radiator not full of corrosion, fan clutch in good condition, etc, then it should run less than 220 degrees in just about any weather. When new, these cars were meant to be driven, only the L88's would act up - due to no fan shroud for low speed operation. I have a 489 stroker L89 in Orlando and even when the outside temp is in the 90's, the car does not overheat (with a TOTALLY stock cooling system).

Good Luck,
Mark

[Joe T.]

Re: It shouldn't run hot

I agree. I don't subscribe to the rumors that these cars were unnaturally subjects of overheating. Chevy had enough experience to design them correctly. I think the rebuild I an doing now, including repairing or replacing the front air dam, the shroud and seals and the 5 versus the 7 blade fan should fix or help with the over optimal temp scenario. It would seldom overheat under any circumstances, just run around 200 (if the temp guage was correct). It had gotten hot enough on at least one occasion that I ran the heater in some HOT weather to pump hot enough air through the defroster diffuser on the dash to warp it. I was a witness and party to that episode.

Having said that, this is my opportunity to put everything right to resolve these and other issues. Bottom line: I agree with you and I simply have a problem requiring corrective action...Thanks and regards...joe

[Joe L.]

Re: It shouldn't run hot

joe-----

The correct 7 blade fan will provide a little more cooling effect than the 5 blade fan otherwise used for 1969 Corvettes. However, the amount is minimal. Very early in the life of my 69, I replaced the original 5 blade fan, GM #3888366, with the 7 blade fan, GM #3955182. It made VERY little difference in engine cooling, but there was some slight, observable difference under some conditions.

For the cooling system in a Corvette to work properly, ALL of the components of the system have to be "just right". If ANY are compromised, cooling problems may be observed under certain circumstances. I can tell you, for sure, that fan shroud seals and radiator seals are absolutely critical.

Another component of the cooling system that I found "weak", even in brand-new condition, is the 60-70 style fan clutches. Under maximum cooling requirements, these things just don't pull enough air. I solved that problem, once-and-for-all, by installing a later fan clutch. However, installing a later fan clutch on any pre-71 Corvette does involve some other parts changes and some modifications which some folks might find a little tricky. All of the mods are easily reversible, though, if one wanted to return to an original style set-up.

[Joe T.]

Re: It shouldn't run hot

Thanks Joe: I am trying to bring this thng up to optimal performance in this critical area. My fan/clutch assembly has a SLOTTED attachment to the water pump which, if I remember a previous post from you, is not factory original. I will try to get this thing in line and preforming with the factory STYLE (if not parts) configuration. I will test the fan clutch once its running (that may be some time yet) and I can always just put a clutch eliminator on it. I didn't realize the importance of the shroud seals when I originally had these issues arise. It wasn't a constant problem, just under some limited but not extreme circumstances. If the clutch seems to be a problem, I will just go with a clutch eliminator and endure the extra noise and potential power drain, neither of which seem significant in my applications. Thanks again and I am STILL hunting that 3955182 fan! Regards...joe

[Joe T.]

Re: It shouldn't run hot

By the way....2 7/8 inches from center to center,,,jt

[Joe L.]

Re: It shouldn't run hot

Joe----

That says that it's a pre-71 fan. However, I don't know which one from the numbers.

[Joe L.]

Re: It shouldn't run hot

Joe----

Slotted flange fan clutch is always AFTERMARKET, although sometimes one sold by Delco.

[Joe T.]

Re: It shouldn't run hot

Thanks Joe.
That's what I remembered from your previous post.
Does an aftermarket clutch (or any service part) from DELCO qualify as original as long as it was the correct service part for the application?
I will clean this one up this week and see what's on it as far as identifying marks (if you're interested in helping me decode this).
As always, I appreciate your response, assistance and most of all, your knowledge.
Regards...Joe
PS: Since this should have general interest here, I will keep this public as opposed to emails?