Hello All: As I wait for my heads to be inspected from the shop I am replacing my water pump and all the hoses. My question is I purchased a heavy duty fan clutch which will move the fan about 1/2"closer to the radiator. Is this a problem? Thanks! Merry Christmas
what is the part number for the clutch? i ordered an HD unit and eventually sent it back. it would not disengage ever. it drove me nuts.
The pic is not clear enough for me to see the relationship between the parts. I would get the factory repro from the Parts Place. I too dislike the heavy duty truck types.
Now I am really confused, not sure what clutch I need, all the information I can find is the one I purchased is correct. The Delco part number on the one I am replacing is 4974369, which is no where close the the ones in my assembly manual which for a 400 non-stage 1 with AC is part # 1377856 or 5358797.
The factory part numbers in the assembly manual wouldn't correlate to the clutch you currently have on the car even thought its technically a GM part. The one you have on the car is a replacement Delco fan clutch. Delco probably consolidated the numbers down at some point so one new part number superseded a whole list of original numbers that were obsoleted. The "born with" fan clutch would be a non thermal and the mounting flange would have holes not slots
Good information, not interest in an original one, just a good replacement unit right size and fit, but what is the right fit? Above said the Parts Place and yes the dimensions on one if them is correct for the one that is in the car now, but the one I just bought matches the other unit dimensions so what dimension is correct for my car one is 2-3/4 from the mount to the fan base the other is 3 inch what is the dimensions I need for my car?
Here is a good, short article with part numbers from Buick Performance Club. http://www.buickperformanceclub.com/FanClutchInfo.htm
After reading this, I realized my long nose water pump has the fan almost completely into the fan shroud. It seams like the fan never disengages (thermostatic), maybe its too close to the radiator?
Two problems. 1. Unless you have a very unusual fan, the heavy-duty fan clutch will never properly disengage 2. The fan may be too deep into the shroud. 1/3 in, 2/3 out is optimum. 1/2 in, 1/2 out is acceptable. Yup. Very few automotive (non-truck) fans present enough drag to get a HD or Severe Duty clutch to disengage. Non-thermal clutches were invented for people too cheap to buy a real fan clutch. To add injury to insult, they also don't have as long of a service life as thermal clutches. In short, non-thermal clutches are cheap junk. It is too close to the radiator. That MUST be fixed. A fan too deep in the shroud CANNOT move air properly--the air "recycles" back into the shroud, blocking airflow through the radiator. Whether it is engaging or disengaging is another matter. Many folks think a disengaged fan clutch pulls a lot of air--I've seen people mistake a disengaged fan clutch for one that's engaged. Then they actually hear one engage, and they're astounded. Are you SURE it's engaged? Do you hear it engage?
I've been through a few fan clutches over the 17 years I have had my 70 GS455 back on the road including a centrifugal unit (which I thought worked well but only lasted one summer and about 3K miles) to a HD unit (2747) that was recommended by many here on the board. I ran the HD for several years but the car sounded like a wind tunnel 1/2 the time and this year it developed a vibration so I went back to a standard duty unit. All this time though it bothered me that the fan was BURIED in the shroud and I knew that was less than desirable. So yesterday I was looking at the link to George N's article about fan clutches and part numbers and I had a memory flash... Rewind about 18 years and I remember when I bought my 70 GS455 and started tearing it down for the restoration that getting the fan off the water pump was a pain in the rear because the nuts were so close to the back of the fan clutch. Because the fan clutch was a stumpy little bastard like the Hayden 2765 shown in the list! I immediately ordered one off Amazon and it should be here in a few days. Granted I have several months before I will get to really use it but I'm looking forward to giving it a try summer 2017! Taking at least .600 inch of length out of the assembly should put my fan position at least half way in/out of the shroud VS the nearly buried condition I have now. I'm hoping that this little change will help things run cooler. Add on 2 hours later.... After a bit of research it appears that the 2765 will probably work and is listed as a standard duty thermal fan clutch. The pilot hole spec is a bit shallow but I'm sure about 30 sec in the drill press can resolve that. For what it's worth this is shown as being for a Jaguar application. The 2947 is a HD fan clutch with most dimensions being the same as our standard fan clutch but with the shorter 1.09 fan height VS the 1.53 or 1.62 listed for most other typical fan clutches for our vintage of automobile. I will report back with actual delivered dimensions of the 2765 after it arrives next week.
Really short, really hard-to-work-with because the shaft is so short the hardware is difficult to get to. Comes with a bushing to reduce the diameter of the pilot? Yeah, I have that one on my Toronado.
