Hi,

I just put a new 454 in my 1966 SS and would like to convert from the factory 5 blade manual fan to a thermal clutch set up. Engine dynoed 625HP at the flywheel but when I hade my car chassis dynoed it was only making 484 at the rear tires. I realize that some drivetrain loss is expected (~15% with manual tranny, no power sttering, AC, etc...) but I believe that I'm losing a good bit through the manual fan always spinning (not to mention the undethood turbulence created by the fan).

I was wondering if anyone new what chevrolet parts might still be available to convert my setup to thermal clutch ( I don't think a clutch fan came on any 66 SS???). I am running a short style water pump and factory shroud. If it makes any difference I am using march serpentine 6 groove pulley system.

I'm looking for chevy part numbers for thermal clutch assembly and matching fan.

Thanks for any suggetions of references,

-Ken Jett

Ken,

I think that there were thermal fans available with the cars equipped with A/C or heavy duty cooling packages. My '65 has heavy duty cooling and no A/C, and had a thermal with 5 blade fan on it. Get one of the many Vette parts catalogs and I'll bet you can piece just about anything you need to cool her and will look right too.

'65 Maliblue 406SBC/PG TC #811

Site sponser "Ground-up" has the stuff. An original NOS '64-'68 w/short pump is $120 or so, a replacement is $60 or so. A 5 blade fan is $70 and a 7 blade is $90. All the stuff is shown as '65 to '68, no mention of BB or SB.

Well I used the "kit" from ground up, got the 7-blade fan and clutch. I also replaced the shroud. works great: now there are a lot of opinions on this, it sure seems like I replaced water pumps and clutch fans a lot in the 70s. There is a correlation, think they wear out the pump bearings. In fact, Stewart specifies not to run fan clutches with their water pumps-- anyway you should pick up 10-15hp with a clutch, also reduce turbulence and "harmonic vibration" as I understand it,

You can purchase a fan and clutch from Flex-a-lite for around $100. I know this is not GM, however, I would not be suprised if some of the parts sold by restoration suppliers were from manufacturers like this.

Steve R.

Thanks to all who replied. Is there a significant advantage in going with a 7 blade fan vs. a 5 blade fan? Otherwise I think I will keep it close to orignal and use the 5 blade.

Thanks again.

-Ken Jett

Ken, that 5 blade fan is an undesirable, cheap production item (hope I don't offend anybody). The 7 blade, as I understand it, is part of a heavy duty cooling option. flows more cfm's- consider 4-core rad also. This is one of the upgrades I've been very satisfied with, in terms of fit and "factory" appearance..

Thanks for the reply, Leeds. I already have a 2 row (1.5") Giffin radiator. My problem is not with keeping the engine cool (runs 180 degrees and not a degree mote), I'm just trying to free up a few horsepower and reduce the underhood turbulence. By the time I saw your reply I had already ordered the 5 blade from Ground-Up. I have a five blade currently and no problems. I was told by the GU rep that this was an OEM piece so I don't expect to have any problems.

Thanks,

-Ken Jett