Configuration of fan blade tip 71-72 vs. 73, 454 with AC

[Mike E.]

The first two pictures are of a January 73 fan blade. Are the "blunted" tips correct? If so, why did
GM change them after 1972 and the pointed tips. (second two pictures)
fan blade 73 454 ac (1).jpgfan blade 73 454 ac (2).jpgfan blade (1).jpgfan blade (2).jpg

[Mark F.]

Re: Configuration of fan blade tip 71-72 vs. 73, 454 with AC

Noise reduction based on tip design??

https://www.caeses.com/blog/2019/axial-fan-noise-reduction-how-to-boost-it-with-smarter-geometry-models/

[Mike E.]

Re: Configuration of fan blade tip 71-72 vs. 73, 454 with AC

So, is the blunted tip correct for 73?

Noise reduction based on tip design??

https://www.caeses.com/blog/2019/axi...ometry-models/

[Mark F.]

Re: Configuration of fan blade tip 71-72 vs. 73, 454 with AC

So, is the blunted tip correct for 73?

I don't know - I was only speculating on your "why did GM change them after 1972 and the pointed tips" part of the question...

[Tom L.]

Re: Configuration of fan blade tip 71-72 vs. 73, 454 with AC

I'm not to sure any of the fans should have a "blunted" tip. Before I found a correctly dated fan for my '72 I had a '73 fan. Had the same tips that my '72 fan has. I've seen a number of fans with tips that have been trimmed or bent to prevent interference though.

[Bill B.]

Re: Configuration of fan blade tip 71-72 vs. 73, 454 with AC

Mike,

The Summer edition of the Restorer (Vol 48, #1) has an outstanding article on '53 - '82 Radiator Fans by Joe Tripoli. He has several tables of part #s and photos of configs.

According to the article, the P/N you show is correct for your BB w/ A/C, however, outer blade shape is indicated to be pointed finger.

[Robert Y.]

Re: Configuration of fan blade tip 71-72 vs. 73, 454 with AC

Mike, my '73 454 with ac that was built on Jan. 31,1973 has the fan that is shown in pics 3&4. I don't know why they were changed from the '72

[John S.]

[Owen L.]

Re: Configuration of fan blade tip 71-72 vs. 73, 454 with AC

Regarding the years of it’s application, Joe’s information lists it as the same fan for ‘71, ‘72 and 1973 w/LS4 and C60. While I do not have a 71/72 TIM&JG, I do have a ‘72 AIM and the illustration confirms the 3992095 fan in that application and it shows the pointed tips.

Yes, the '72 LS-5 with AC has the pointed blade 3992095.

[Tom L.]

Re: Configuration of fan blade tip 71-72 vs. 73, 454 with AC

This style fan was also used on '70 454 w/ a/c. Blades are the same pointed tips but the bolt circle is different. How do I know?? Was overzealous and did not check and bought one. When I realized I had made the mistake I was embarrassed. Spent all that $$ for the wrong part. Didn't tell the wife and I let it sit in the box in my basement for over a year before I told her.

Ultimately I did find a good home for it. Perhaps a '70 owner will chime in and confirm. In my experience I feel VERY comfortable saying that all years using this fan were supposed to have the tips. But many have been modified.

[Joe L.]

Re: Configuration of fan blade tip 71-72 vs. 73, 454 with AC

This style fan was also used on '70 454 w/ a/c. Blades are the same pointed tips but the bolt circle is different. How do I know?? Was overzealous and did not check and bought one. When I realized I had made the mistake I was embarrassed. Spent all that $$ for the wrong part. Didn't tell the wife and I let it sit in the box in my basement for over a year before I told her.

Ultimately I did find a good home for it. Perhaps a '70 owner will chime in and confirm. In my experience I feel VERY comfortable saying that all years using this fan were supposed to have the tips. But many have been modified.

Tom------


I don't think the configuration of the blades ever changed at least as far as GM was concerned.

There were actually THREE different part numbers. For 1970 only the original part number was GM #3969926 and, beginning late in 1970, GM #3993889. I don't know what the difference was between these two parts but I don't think tip configuration had anything to do with it. For 1971-73 the only part number was GM #3992095.

[Tom L.]

Re: Configuration of fan blade tip 71-72 vs. 73, 454 with AC

Joe, I agree completely on the blade configuration and I am aware that there were 3 part numbers. The 926 and 889 both had the smaller bolt circle for the '70 water pump and the 095 had the larger.

Just for kicks I searched for fans on sale. Below is a pic of a 095 fan currently for sale on ebay (not mine). If you zoom in you can see that the tips are bent over, away from the shroud if installed. likely to prevent them from touching the shroud. I think the seller might have not provided a side view to hide that. It is repairable though


095 fan.jpg

[Joe L.]

Re: Configuration of fan blade tip 71-72 vs. 73, 454 with AC

Joe, I agree completely on the blade configuration and I am aware that there were 3 part numbers. The 926 and 889 both had the smaller bolt circle for the '70 water pump and the 095 had the larger.

Just for kicks I searched for fans on sale. Below is a pic of a 095 fan currently for sale on ebay (not mine). If you zoom in you can see that the tips are bent over, away from the shroud if installed. likely to prevent them from touching the shroud. I think the seller might have not provided a side view to hide that. It is repairable though


[ATTACH=CONFIG]109580[/ATTACH]

Tom------


Yes, the only difference between the 3969926/3993889 and the 3992095 is the fan clutch bolt circle and the size of the center hole. I just don't know what the difference was between the 3969926 and 3993889.

It MIGHT BE that the 3969926 and 3993889 used different blade material. One might have been steel and the other aluminum and/or other differences.

[Tom L.]

Re: Configuration of fan blade tip 71-72 vs. 73, 454 with AC

I've had the 889 in my hands, definitely aluminum. Can't comment on the 926. Maybe there's someone with the 926

blade that has a magnet. Would put this to bed. For now...

Throwing it out there. Anyone have one of these fans that might be wrecked? It's a curiosity.

[Mark E.]

Re: Configuration of fan blade tip 71-72 vs. 73, 454 with AC

Did 1974 LS4 C60 not use the 095?