A friend of mine picked up a 7 blade clutch fan from a 1970 Caddy I believe. Will this work on my 66 chevelle. I know it fits in the shroud as It is the same size as my 6 blad flex fan from summit. Will going to the clutch fan be a good move if it works? Should I stay with the 6 blade flex or put the flex on the clutch instead of the 7 blade caddy fan? I am wanting the best set-up for e.t. at the track.

The flex fan is better for HP. The 7 blade is better for cooling in traffic. If you want more HP, install an electric fan. You won't get any benefit buy installing the flex fan on the clutch

Thank you for the info.

Perry,that 7 blade caddy fan will cool better in traffic esp if you run a HD thermostatic fan clutch.

The nice thing about a clutch fan is when you get into the the throttle the clutch will cut out at high rmp thus loosening up some more power which is the one purpose of the design as is better fuel economy too.

Also,the fan is never fully engauged untill the motor is hot enough to required additional cooling which causes the thermostatic coil on the front of the fanclutch to lock up the clutch to egauge the fan for more cooling/airflow.

There is free power here because the fan is only fully engauged when when additional cooling is required like in stop go or slow moving traffic.

GM was not stupid when they installed clutch fans on all the high reving high perf motors to free up a few more ponies in the 396/425 hp(1966 only) & 427 vettes,396(402)/375hp in chevelle/nova/camaro, the LS6 454/450hp chevelle ,the 302/290hp(really like 330-340hp) z28,or the LT1 350/370 in vette & 350/360 in Z28 all high reving solid camed motors.

So i would say yes the clutch fan will save a few ponies over a flex fan which has been proven on the dyno mult times before in Hot Rod & Super Chevy articles i have read in the past to perform better than flex fans for cooling 7 using less power to run them esp at higher rpms when the clutch fan cuts out for optimal power/perf.

If you decide to use the clutch fan dont use a used/old fan clutch because your asking for trouble,just bite the bullet and get a new fan clutch when you install that 7 blade gm fan. Make sure the fan blades are at least 1/2 way to a max of 3/4 way into the fan shroud for proper cooling.

If you feel your setup could have a tendancy to run hot get a h/d fan clutch for A/C that will engauge at a lower temp but if you feel your setup runs cool then get a std fan clutch. But keep in mind the std clutch engauges at a higher temp so your motor will run a little hotter in traffic.

Scott

Thanks for the info Scott! I will go with the fan and get a new clutch for it. Are all the clutches the same size or will I need to measure to make sure I get the right one?

Well the fan clutched were mostly std in late 60's-early 70's but i am not sure in gm used the same 7blade clutch fan on 70 caddy & 70 chvelle.

I would get a fan clutch for a 70 with same size moroe your runing & see if it fits the 70 caddy fan,if yes great.

But if the 70 chevy clutch does not fit the 70 caddy fan then you could try a 70 caddy fan clutch but i doubt it would fit a 70 chevy water pump.

In that case you would have to scam up a 7 blade clutch fan for a 70 chevy which you could get from yr one ,watch ebay for an original blade fan(typically go for $50-$300 depeding on cond/bld date/pt#),look in T/C parts for sale adds ,or place a wanted add for a 7 blade fan in T/C for a fan.

Scott

Hello, what pitch is the fan blade there is a difference on standard and HD clutches. HD requiring more pitch to get clutch to disingage. Match clutch to the fan you have, hope this helps.
Gary.

FWIW I recently installed a 5 blade fan from (I think) a '78-'83 Malibu. I had to replace the clutch fan (as it wouldn't bolt to my water pump) but that was merely a trip to Idiotxone and spend $49 for the correct part which by the way works well.

Ever seen a flex fan come apart? From what I hear they're notorious for this, and the results aren't pretty......