A/C Clutch Differences

[7173Vert]

Ford used a different AC Clutch Assembly on the 302/351 and the 429 series engines. You can see the difference in the pulley counterweight although the rest of the magnetic clutch assembly appears to be the same. I’m sure it’s an engineering issue at the time, more then likely to do with the drain on the smaller engines when the magnetic clutch engaged. I guess they felt that the 429 could handle the power drain with a smaller pulley size. My original set up is whining (bearing) and of course I  only have a NOS unit for the smaller engine on hand... 
 

I note that the bearing can be replaced (Motorcraft YP-20 PT#). NPD is out of stock… I'm looking for other alternatives at the moment.

I was thinking of temporarily installing the larger one on my car until I can get the bearing and then re & re on my clutch assembly…  I dont see an issue unless someone here feels otherwise? 

Thoughts?

 

[7173Vert]

Well I’m interested in this so I’ll reply to myself, lol. 
 

As noted in the picture below the larger 302/351 clutch assembly will not work on the 429 car’s. I’ll just leave it at that…
 

The second picture shows the considerable size difference between the two pieces. The 429 set up is about 6” across.The 302/351 unit is about 7 7/8” across. The width dimensions are similar. Additionally, but not shown here, the actual clutch mechanism and belt pulley size is different by about 1/4” in circumference width. This would equate to an rpm difference in pulley operation as well as possible belt size difference. There is a difference on the idler and adjustment pullies between the engine sets ups ( hence why the larger AC clutch pulley was hitting the bolt in the picture below).

I’ve ordered a complete replacement coil and clutch assembly specific for my engine. I’ve also ordered a new clutch mechanism bearing that I will install in my orig C9 clutch assembly and then look to return it to the car in the future.

For those that may have to go though this repair in the future on their car, a heads up: Buy a short 2”X5/8”x11 bolt in order to remove the clutch mechanism from the compressor.

 

[secluff]

Hello Ken,
Sorry for a very delayed response. Due to a storm last night, I lost internet service until just recently. I see where you have decided on the type of repair you want to do.
Here is what I almost got to post last night!!  :biggrin:
I was in a similar dilemma when installing a "New and Much Improved" 429 in my '72 N code Gran Torino Sport. My AC compressor clutch was damaged beyond repair. The only parts car I had at the time was a '73 H code Mach 1. I noticed the differences in the pully and counterweight between the two engines and regrouped. It was already too easy to blow up a York compressor (ask me how I know that!), and I didn't want to chance it with a pully/clutch assy not listed for that application. You had mentioned that the engineers felt the 429 could absorb the power drain of the clutch engaging better than the smaller displacement engines. That became an issue on the newer model vehicles when only 4, 6, and smaller displacement V8's were available in the car lines. The clutches you'll see now have what looks like rubber blocks which are absorbers to minimize the surging felt when the clutch engaged on an already struggling engine!
The bearing you need is Ford C9AZ-2990-A (Motorcraft YP-20), and NPD in Flordia shows inventory on that bearing. If you have a favorite parts store, you might see if they can cross the Ford/ Motorcraft part number or industry number 5106WCC. Online sources such as Rock Auto and E-Bay usually have these types of bearings listed. I have also used Green Sales (800-543-4959) http://www.greensalescompany.com/, specializing in NOS/Obsolete Ford parts. They showed 19 C9AZ-2990-A in inventory. When Ford discontinued the C9AZ-2990-A/YP-20 and the replacing C9AZ-19D666-A/YP-20-A in the mid-'90s, the retail price was $28.85, so the prices now are not in the crazy zone like everything else!
Ultimately it's your car and decision, but on something that has more than a pristine underhood appearance, I would be more inclined to do a "Once and Done" to minimize the chance for underhood paint or any "Accident" damage!
Hopefully, this will help give you some additional options to consider while allowing some price shopping. 

 

[7173Vert]

Thanks Steve, I figured you would chime in when you had the time as you love these Ford part's dilemmas that pop up... I did put a second response above where I clarified my position. I'm not taking any chances with the J Code Vert. The bigger D2 assembly will work as a replacement on my 73 Coupe if I ever need it, so it is still nice to have. Thanks for the input, as always!

 

[7173Vert]

Installed the new A/C clutch bearing today. I did order an additional aftermarket complete clutch and coil assembly as back up, but I wanted to keep the original C9 Ford Pt# piece on the car… The new $27 bearing plus a few hours of careful tedious work paid off. I painted the assembly and will reinstall on the car and then the engine bay will lose its high pitched sound… The original bearing lasted great, but you can feel the dried up internal grease and hear the obvious slight grinding…this want going to end well if I didn’t address it soon. The fact the car hasn’t been run much the past few years, gave me little motivation to address this, but now it is a different story.

 

[Hemikiller]

Excellent, glad it worked out.