In an attempt to help more customers with heating issues on their 70-73 351c and get away from using a flex fan I am looking for the “best” clutch to use. Most of our customers have been happy with the clutch we use on the 67-9 but at least one customer says it crowds the AC pump. If anyone has pictures of a successful install or feedback I would love to hear from them.
I used a aftermarket replacement clutch with the stock '69 351(W) AC fan on my 408C. Fits like it was factory.
Do you know which part number clutch? Got a picture? Does the clutch sit about 2" away from the rad?
Hayden 2710. No picture. Clutch sits 15/16" from (aftermarket 3? core AC style) radiator.
I found that Hayden 2711 was the shorter one to use on my big block cars, and even then there was not as much space between rad. and fan as the factory one.
Hi,
I’m the guy with the crowded A/C clutch that Don referred to above. I’ll go ahead and tell my story from the beginning.
I’ve got a '70 Cougar 351C-4V with A/C and PS. It already had the 24" 3 core radiator.
I saw Don’s WCCC video on cooling system upgrades and decided to try it. My original '70 Cougar 351C-2V with A/C had some cooling issues in traffic with the Texas heat and the engine block corrosion/fouling condition of the current one isn’t well known.
I purchased the fan, clutch, and fasteners from WCCC and installed them and had some issues.
- I discovered that I had almost no clearance between the back of the fan blades and the A/C compressor clutch. With the any engine movement there would be contact. Note: The Sanden type replacement compressor in the car sits forward about a 1/2" more than the original York. The back of the new fan sits back an 1/8th" or more than the flex fan. The flex fan’s smaller diameter and curved blade ends left lots clearance.
- A lot of the new fan is exposed behind the fan shroud (almost 1-1/2" at the top) and with the full diameter it left me uncomfortable from a safety stand point (lots of years of industrial safety training and machinery safety programs and some common sense will do that)
- Blade spacing from the radiator was a bit over 2" and there are claims that closer is more efficient (no closer than 3/4").
I sent WCCC an email and got a prompt response from Don both by email and phone with some thoughts, suggestions, and an interest in getting it right, even if I needed to return all of the parts. He encouraged me to post my findings. I had already started exploring other clutch options which I have since pursued and will share here with a lot more information than I had when talking to Don.
Hayden Automotive (also under the Murray name) manufactures a variety of these clutches. WCCC has been providing the Hayden #2765 (WCCC #10303) which has face of drive flange (water pump pulley) to fan mount dimension/length of “H” = 1.09". A commonly used '69-70 Mustang clutch (#2710) has an H=1.75", however that clutch does not match the fan mounting dimensions for WCCC’s 7 blade fan. Hayden makes a #2706 that matches the H=1.75" dimension, the WCCC fan mounting, and all of the others for the #2710 (and all, but the H dimension of the #2765). The drive end / water pump flange diameter is larger but it still accommodates the 4 - 5/16" bolts on the 1-3/4" bolt circle for the drive flange (a detail the Hayden dimension table does not tell). Note: the #2706 accommodates only the 5/8" diameter pilot which is okay on the 351C. The H=1.75 clears my A/C clutch by better than 5/8", it tucks all but 5/8" of fan into the shroud and reduces the radiator to fan distance to an average 1-1/2". Note the fan to radiator spacing is about 3/8" closer at the bottom than the top and the clutch is about 3/16" closer to the radiator than the fan.
Other options:
- Hayden makes a 2707 with a H = 2.03 (also 5/8" pilot only) which would move the fan further forward (note my radiator has a tie rod across the back at mid level which reduces the clearance further. I thought the “Ford” H = 1.75 would be enough, but this additional amount would appear to work.
- Hayden makes a 1/2" and a 1" spacer (#3960 & 3982) for the drive flange, also 5/8" pilot. The 1/2" spacer will be a close fit on the pilot hole depth, the one I measured at the auto parts store was about 5/16" deep with the boss on my water pump being about the same when measure with a ruler.
Observations:
The fan radial clearance to the shroud is tight. I’ve got a plastic (not the fuzzy FRP one in Don’s video) Ford D0ZE 8145 shroud and have a 1/4" to 3/8" radial clearance at the sides and just a bit more top to bottom (the hole isn’t quite round). I have not yet road tested the installation with high engine loads shifting the engine on the mounts. The slotted holes on the shroud limit centering it side to side, a good thing if it is correct, but may need to deepen the slots on one side to slide it over if there is any sign of contact.
The “H” dimensions referenced above should have been “E” Fan Mount Height to match the Hayden dimension chart. It’s still the distance (shaft length) from the water pump pulley face to the fan blade mounting surface.
The #2710 and #2711 clutches referenced above match a 2.37’ fan mount diameter with a 3.00" bolt circle. The WCCC fan is a 2.62" mount diameter and a 3.25 bolt circle. The #2711 “E” dimension is 1.40" and both allow for 5/8" or 3/4" pilot diameter (w/ a bushing).
There is also a #2705 with H = 1.53", it too with a 5/8" pilot only.
All of the clutches with the longer shaft lengths are a lot easier to install since there is clearance to install the bolts with out juggling the clutch forward clear of the mating surface to feed the bolts in.
There are three things going on here:
- Making sure the fan and clutch are compatible. This has to do with the bolt circle diameter.
- Making sure the clutch and the water pump are compatible. This has to do with the diameter of the shaft coming out of the water pump.
- Making sure that the fan doesn’t and can’t hit the radiator. Engines move around. The fan won’t move much relative to engine mounted accessories, but remember that the engine does move relative to the fixed radiator and shroud.
There are actually two different, but very similar, fans available.
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The C8OE-B has a 3.00 inch bolt circle. It matches up with the #2710 (long) and #2711 (short) clutches. The C8OE-B was originally used on the '68 and '69 390 427 and 428.
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The C9ZE-E has a 3.25" bolt circle. There are several clutches that match up. The 2765 is the closest to the original used in the 428 Cobra Jet application. The C9ZE-E was originally used on late '69 and '70 390 and 428.
The C8OE-B fan has slightly less pitch, over all it is 2.17" deep. The C9ZE-E is 2.2" deep. They were probably supposed to be identical, but for what ever reason, there is a very slight 3/100" difference. There is no measurable difference in the amount of air either fan will move.
In late '69 Ford decided to increase the size of the shaft in the water pump from .63" (5/8" to .75" (3/4") The change also allowed for a larger, more durable, bearing in the water pump. There are water pumps out there with both shaft sizes. Most fan clutches that have a 3/4" opening also include a reducer that makes them compatible with the 5/8" pumps. YOU MUST USE THE REDUCER if you use a clutch with a 3/4" opening on a pump with a 5/8" shaft. Bad things will happen if you don’t.
On the front of the fan clutch is a bimetallic spring. It reads the temperature of the radiator and when hot it twists the valve that diverts the hydraulic fluid inside the clutch to make it start to lock up. If it is too far (more than about 2 1/2") from the radiator it wont get hot enough. Too close, under 3/4" is probably too close for most motor mounts in a panic stop situation.
Just a bit more of background.
The initial set up on my 351C had a 2-1/4" spacer between the water pump pulley and the flex fan.
The total distance between the radiator face and the water pump pulley face is 4-1/2".
The 5/8" pilot shows at the fan mount on the spacer. I don’t know if that will always indicate a 5/8" pilot/shaft at the water pump.
If you’ve got 5/8" pilots I would recommend the 2706 clutch with the 3.25" bolt circle fan, but there are a variety of choices if your spacing is different.
If you’ve got a 1/2" pilot and the 3.25" B.C. fan there are no currently apparent choices other than the short 2765 clutch.
If you’ve got a 3.00" B.C. fan there are a number of choices as well.
Here’s a pic of my '70 351C with aftermarket A/C. The car had this clutch fan setup when I got it prior to adding the A/C. You can see there’s almost no clearance but I’ve not had any issues.
I don’t know what type of fan or clutch this is. Is there a number somewhere I can look for?
FWIW, zero cooling issues even in Tejas.
Wow, that is close to the AC pump, how far is the clutch to the rad? This is what Tom was trying to balance out, he too had an after-market ac pump. There should be a number stamped on your fan.
Don, I’ll check those things tonight.
Don,
Fan blades all have C60E on them. Fan is about 1.75" from radiator.
Edit: I mean tips of fan blades. Clutch is somewhat closer to the rad.
Here are some pictures of the Fan and Clutch installation on my 70 351C-4V:
First the longer shaft 2706 Clutch with clearance and most of the fan in the shroud. The bolts to the water pump pulley are much easier to install as well. My recommendation if you have a 5/8" water pump shaft/pilot, as I think all the 70 351C’s, do use the 2706.
Second the short shaft 2765 clutch almost touching the aftermarket A/C pulley and significant fan exposure behind the shroud
Very good information here. I need to go look at the clearance on the 351 with sanden compressor in my sons car.
Looks like I need to switch to the 2706 next time I’m in there for anything.