I took the car out for the first drive today and one problem of many was the fan. As soon as I left it was deafening like a class 8 truck. It's a 68 Cutlass wagon with a recent 455 swap. I checked it against OEM parts and it has the long water pump, 3 groove water pump pulley (5 3/4"), 3 groove crank damper (7 3/8"), all matching for A/C. The problem is with the 68 (presumably non-A/C) fixed fan it's remarkably noisy, as you'd expect being driven 30% over stock. What's the correct factory configuration for this? Clutched or a different fan? Are there any differences in clutches or any other parts that have to match?

 

I'll take a stab at this. I had a '70 GTO (non A/C) that came from the factory with a flex fan. It was just downright loud on the road over 30mph and I finally got tired of it. With that car, all I did was remove the direct fan drive and the 4-blade fan and install a fan clutch. I got a correct fan from a junkyard Pontiac for the fan clutch and it made all the difference in the world as far as reducing noise. It didn't lose anything in cooling, either.

I believe you are right (don't have my reference books with me) in that a bare-bones car (no A/C, no heavy duty cooling, no heavy duty radiator, etc.) came with a straight-drive 4-blade fan. I'm assuming your car has A/C and therefore your pulley set-up is something that would come with A/C or heavy duty cooling. But it should also have a clutch-fan set-up. I'm thinking you should be able to remove the straight-drive 4-blade fan assembly and install a fan clutch with the correct fan (Olds used a 6-blade clutch fan in '68 & '69) and I believe that it would work as well as reducing the noise level.

Does your wagon have a fan shroud? That could play into this as well. I'm just trying to draw this from memory but I believe the 4-blade straight-drive fan set-up didn't use a fan shroud, where as the clutch fan set-up does.

Randy C.

 

It's got the 68 6-blade fan with a shroud. I guess I need to dig up a clutch and fan.


Anyone know if other GM products used a similar bolt pattern and fan size?

 

I'm thinking the 6-blade fan you have now, if it's the correct one, will also fit a fan clutch. I'd obtain a fan clutch first and see if it works out with your current fan. I got the fan clutch for my '68 from NAPA. It looks very similar to the correct style fan clutch used in '68.

Randy C.

 

The stock 1968 non-A/C fan is a four blade fixed. The correct A/C setup for a big block should be a six blade 19" fan with a clutch. The fans designed to bolt to a clutch cannot be used in a fixed (non-clutch) application because the bolt pattern is different. The clutch bolts to the water pump, not the fan in that application. All Oldsmobile water pumps have the same four bolt pattern.