ROCKET VAPOR

What does the "74" that is ink stamped on my fan blade mean???

I this a build sheet code for the fan???

Does anybody have this stamp???

The car is a 1970 442 with A/C, AT, and HD cooling. March of '70 build at the Fremont plant.

IMG_0975.jpg

bobb

Hi Lance,

The fan codes, as well as the fan clutch codes are listed in the factory Chassis Service manual.......but I don't have one in front of me......the They should be in the "Cooling System" section. I think Inline Tube would have that stamp....or could easily make it for you.

regards,
bob

bobb

Lance,

According to the 70 Olds Chassis Service manual an A Body with AC or HD cooling should have a 19.5" diameter 6 bladed fan stamped "H" and "FRONT" on it. There is no "74" stamp code listed at all. The fan clutch for your application should be stamped "OR".

regards,
bob

Rocketbrian

I am restoring a 71 442 without A/C or HD cooling and there is a 443 stamp on one of the blades. I looked in the assembly manual and that is the last three digits of the part number. The actual part number of my fan is 405443, per the parts book. Perhaps the 74 is the last two digits of the part number for your application. Perhaps this helped on the assembly line. In the case of non-aired cars, the 350s had a 19" fan and the 455s had a 19.5". Hard to believe that would make much of a difference.

ROCKET VAPOR

I will measure the fan tonight to verify the 19.5" diameter.

Is "74" the last two digits of the part number for the assembly line correct fan for my Olds?

I can not find a stamped part number in the blades or the blade support.
Is this normal for the fan to not have a part number stamped on it, or do I need to remove the fan clutch to find the part number stampings?

bobb

Hi Rocket,

A few weeks ago I tried to find a part number on the fan in my 70W and couldn't. But it doesn't seem right that they didn't put a part number on the fan somewhere. So I'm not sure what to tell ya. It may be that they could tell the PN simply by the diameter, as no two fan codes in the Service Manual had the same diameter. Maybe diameter is the answer.

later,
bob

ROCKET VAPOR

Bob, do you know if "74" is the last two digits of the part number for the fan that should be on my Olds?

Rocketbrian

I'm not able to help you any further as I don't have a 1970 Assembly manual. I have worked on several Cutlasses over the years and this 442 is the first one I have come across with a number on the blades. Usually I suppose they are worn or rusted away. When I found the 443 on one of the blades it also raised my curiosity and it wasn't until I checked the approprite section in the 71 assembly manual that it made any sense. Hope you figure it out. I am attaching pictures of the original and after I painted the fan and attempted to duplicate the numbers.

bobb

Hi Rocket,

I looked thru the 70 Chassis Service manual, Engine Assembly manual, and Fisher Body manual and don't see any fan part numbers listed anywhere.

But then I looked thru my 72 Chassis Service manual in the Cooling section and now I see what Rocketbrian is talking about. The fan blade usage chart is ALMOST identical to the fan blade usage chart in the 70 Chassis Service manual EXCEPT in 72 it says:

"For A,B,& C Body - with A/C or H.D. Cooling or W Engine options" the blade identification is listed as "19.5in diameter - 6 Blade, One Blade Ink Stamped "740", Front side stamped "FRONT"

This is probably what is says in Rocketbrian's 71 manual as well.....but it doesn't say it in the 70 manual. So......you're right....what you're seeing on your fan blade is a partial part number....but either Olds just didn't put that little tidbit in the 70 manual.......or your fan is a 71-72 part.

That's about all I got........hope this helps!

regards,
bob

ROCKET VAPOR

Bob, I measured the fan last night and it is a 19.5" diameter. It is a 6 blade fan. It does have the word "FRONT" stamped by the fan clutch. One blade is clearly stamped "74" with no remains of a "0" stamped at the end.

Now I guess that I have too learn how to get an ink stamp made to put this "74" back on the fan blade after I bead blast and repaint.

bobb

Hi Rocket,

Glad we got that mystery solved. ) I don't have an Inline Tube catalog in front of me....but I'm almost positive it says in there they can make any stamp you need. They have a shitload of stamps already made up, so they might have your "74" stamp in stock. I'd give those guys a ring. Or if you have an old time print shop in your town they could easily make the stamp for you.

Take care,
bob

ROCKET VAPOR

Great minds think alike, I have already try Inline Tube's web site with no luck on the "74" stamp, but I will call and ask them tomorrow.

Doesn't Kinko's make these rubber stamps for us hobbist???

BlackGold

If Kinkos doesn't, there's probably a couple other shops in town that make rubber stamps. They'll probably do it for a lot less than Inline Tube, and you can help them choose the font, size, pitch, etc.

bobb

Yo Rocket,

Staples online site says they make stamps....but you'll need to go to the store to pick out the correct font and print size. Really any print shop whether it be a national chain or a mom and pop should be able to make the stamp.

later,
bob

tomsw31

If you take the picture and dimensions into Staples they can make the stamp. Usually they charge $15 to $20 per stamp.

Rocketbrian

I was looking through my 71 assembly manual and I stumbled upon the fan sections for A/C cars. Sorry I didn't look earlier but in Section 6-1 pg 196 it lists fans for 442s. The part number for a 442, with W30, A/C, and or HD cooling is 409740. Therefore it is the same scenario as I suggested, but obviously the 0 is worn off or it just didn't get stamped on your fan. So, the 74 represents the last part of the fan part number. I noticed just as I am typing this 409740 is listed in my parts book as a fan for a 455 from 1971 to 1976 but was superceded by part number 413977. So whether you duplicate the "0" in your stamp is your call. My parts book, for some reason doesn't specifically mention a 19.5 inch fan for 1970. The only fans for 1970 are #401372, 19" with six blades and 19" 4 blade, # 405442.
Perhaps you do have a 1971 fan, for slightly better cooling.

69ho aurora

Hold on a second folks. There is a bit of confusion in this thread.

I've got 70-72 assembly manuals and a Feb 73 parts counter manual in hand and they all seem to agree with the following:

The 70 assembly manual (sec 6-1 page 110) lists 401372 as the fan for all 70 A/B/C bodies with AC or HD cooling. The parts book explicitly lists this as a 19" 6 bladed fan.

The 71 assembly manual (same page) lists 405762 as the fan for A-bodies w/350 and AC or HD cool and 409740 for A-bodies w/455 and W30, AC, or HD cool. Both are list as 19-1/2" in the parts book (and have other non a-body applications as well). The assembly manual mentions CODE "740" for the 409740 part.

The 72 assembly manual (same page) lists 405762 for A-bodies w/350 and AC or HD cool and for the L75 (U code) 455 with an A.T. and AC or HD cool. The 409740 was used for the rest of the 455 combinations. The CODE "740" was also mentioned here.

Note that 70 does not use the same fan shroud as 71-2 (even though last I looked, everyone was selling the 71-2 part number for 69-72. They needed a bigger "hole" for the 1/2" bigger fan when 71 came along. 70 (and 69) use a 402995 while 71-2 use 407867.

There are a series of part numbers and codes for the clutches. I've got to hit the road, but I can supply that if anyone is interested...

bobb

Hi 69HO,

There does seem to be some contradictory info between the 70 Assembly manual and the 70 Chassis Service manual.....and I have no idea which one is right. The 70 Chassis Service manual, on page 6K-8 in Figure 6K-12 entitled "Fan Blade Information" says "A,B,&C Body with A/C or H.D. Cooling or W Engine Options uses a 19-1/2" Dia - 6 Blade, Stamped H & Front. The only 19" diameter fan listed is for an A-Body with 350 cu.in. and that's a 4 bladed fan. No part numbers are given.

Guess I'll go out tomorrow and measure the fan in my 70W.....that should settle it.

Take care,
bob

ROCKET VAPOR

I checked my GM fan shroud last night and the part number 402995 is molded into it in two different places with 1969 and 1970 mold date clocks.

This shroud has a 20 7/8" I.D. opening when checked from side to side, and a 21.0" I.D. opening when checked from the top to bottom.

The car has never had a shroud on it since I bought it though, because I could never align the shroud where the fan would not touch the bottom of the shroud(wrong water pump and worn out motor mounts).

I have allways been told my car should have a 19.5" 6 bladed fan and it does.

So.... nobody has ever seen a "74" stamped on a Fremont built '70 442 with A/C and HD cooling???

Or.... maybe GM had multiple vendors for these fans, and some vendors ink stamped "74" and some didn't???

bobb

Rocket,

Where exactly did you find the part numbers molded into your fan shroud? I went to find them on mine and couldn't. Are they on the outside or the inside, left or right, top or bottom?

thanks,
bob

ROCKET VAPOR

Bob, I found the below information on the inside of the shroud. If it is GM shroud it will not be hard to see this raised printing.

ROCKET VAPOR

Joe, do you have a photo of one of these 1970 19" fan blades with a "H" stamped on it???

These 19" fan blades are like UFOs, everybody is telling me about them, but I have never seen one?

My car is very original, but some high wear items have been replaced.

I want it to be correct at all cost, but I do wonder if 19" was the standard fan and 19.5" was for HD cooling.

Why did Oldsmobile not have these fan blades stamped with the P/N and date code like Chevy does???

The part numbers listed in the Oldsmobile assembly line manual are for the fan/clutch assembly and no P/Ns listed for just the fan blade.

BlackGold

Whew! What a mess, right? Rocket Vapor asked me to double check the fan on my car (1970 442, very original, but no 100% guarantee on the fan). So I did that and also spent some time with the factory literature.

First, my fan measures 19" in diameter, not 19.5, has 6 blades, and the blade pitch is 2". By pitch I mean that if you measure the "thickness" of the blades along a line parallel to the crankshaft, they are 2" thick. The corner of the leading edge of the fan is much more rounded than the corner of the trailing edge. So this fan looks like the black fan in Rocket Vapor's other related post. But it's obviously not the same fan, since the diameters are different. Read on.

For literature I looked at the 1970 Chassis Service Manual, 1970 Assembly Manual, 1971 Engine Assembly Manual, 1972 Assembly Manual, and the Oldsmobile Chassis and Body Parts Catalogs from both April 1976 and April 1982. I'm not going to bore you with every little detail (mostly because I'm too lazy to type it all out). But here's the scoop:

Fan 401372 was 6-bladed, 19" dia, and (I believe) 2" pitch. I could not confirm the pitch in any of the literature. It is the correct fan for a 1970 442 with A/C or HD cooling. Forget what the chassis service manual says; it's the only piece of literature which is not consistant with the others.

In 1971 they got rid of 401372 and replaced it with two new part numbers. 409740 was 6-bladed, 19.5" dia, 2" pitch. It was identified with a stamp of "740". This was the fan that 1971 442s with A/C or HD cooling used.

The other new part number in 1971 was 405762. It was 6-bladed, 19.5" dia, had 2.5" pitch, and no ID mark. This was used on most cars with A/C or HD cooling except the 442s.

Now, just to really confuse us decades later, sometime before 1976 Olds came out with a new fan, 413977, which was 6-bladed and 19.5" dia, and which superseded the previous 409740 and 405762 fans. I assume it had 2.5" pitch, since it would have to cool at least as well as both fans it replaced. Note, however, that the 413977 fan did not supersede the smaller 401372 fan from 1970.

I hope this solves the mystery.

ROCKET VAPOR

Thank you very much for your extensive research on this subject Brian!

I guess I can now put this debate to bed now.....well except for the fact that now I need to locate a 19 inch fan blade