COPO fan clutch problem

[LemansblueCOPO]

Hey, we are currently putting our COPO back together after taking out the motor and detailing everything. The problem we have is that the thermal fan clutch fins are way too close to the radiator. It is an original COPO car with the long water pump and all of the original pieces. Has anyone else had this problem with the fan clutch? Did a special fan clutch go with the COPO cars? Thanks, Steve.

[nuch_ss396]

Steve,

SB & BB clutch assemblies are different. You may have a
SB unit which is longer I believe.

Nuch

[LemansblueCOPO]

It isn't a BB assembly. The problem is that the four-core radiator has the longer water pump. My father remembers running into the same problem in other cars he owned back in the day, but there was a separate fan clutch that could clear on with the big block cars that have the four-core radiators. The problem is no one produces them anymore.

[3macs1]

They are not that hard to locate. I sold two on e-bay in the past 3 months for like 120.00 complete with the fan and I have seen others listed since. Both of mine were off 69 427 425hp engines.The clutch units on these 69's other than the part number were the exact size as the ones on my 70 chevelles one had a 4 core and one a 3 but the same clutch unit.

[LemansblueCOPO]

Do you have any others for sale?

[3macs1]

Hi Steve:
Nothing in that style for sale right now but if you just need the clutch and are not into the numbers matching do a search for fan clutch on e-bay and there are a couple of newer nos replacements that are dimensionally the same.
take care Joe

[nuch_ss396]

Steve,

I've never heard that 3 vs. 4 core radiators used different
fan clutch assemblies. As I mentioned, I do know that the
SB & BB are different lenghts and many use the SB clutch which
puts the fan too close to the radiator. I wish I could
remember the two lengths ( SB and BB ). I'm sure someone
on this board knows or can take a quick measurement.

Since you mentioned COPO, I'm assuming you're doing a BB car.

Steve

[Denis]

There isn't that much space between the fan and radiator even when the correct original BB setup is used. How much space we talking about?

[Keith Tedford]

Our '69 L78 Chevelle has about 2" between the fan and the 3 core rad. A four core should be a good fit as well. Better than an inch of the fan is out of the shroud. All '69 and later Chevelle's ran the long water pump setup. Our COPO Chevelle came with the BO 3 core radiator and I believe that this same rad came on the L78 cars.

[Steve Shauger]

Big block used different clutches from small blocks. The shafts are indeed shorter to accomodate (fan/radiator) clearance for the AC equipped 396 cars and COPO's which both used 4 core radiators. Copo's/L78 used part number 3946050 (stamped CZ)
and L35/34 used the 3946050. I believe the difference between the two had to do with the ability for the clutch to withstand high rpm operation.