old68

my fan clutch is leaking some oil, so its days are probably numbered, if I replace can I add a 7 blade fan? does that help? anyone know where I can get one? would the big block fan bolt on to my 65 327, no ac? thanks again for all the help

larrywalk

I added a 7-blade fan to my non-AC '65 with SBC many many years ago. I felt that it cooled the engine better, especially in city driving.

Where to get one? Google is your friend.

SI67

Might cost more than you were hoping, but here's one source. Since Paragon is a supporting vendor, as I understand things, I think posting this link is kosher.


https://www.paragoncorvette.com/p-36...lade-w-ac.aspx

Gary's '66

I tried a 7 blade on my car ('66 L-79) and while it definitely helped with cooling, it definitely affected the loss of hp. I removed it and am currently running a 5 blade a/c fan.

Gary

mark6669

I have a 7 blade service replacement fan it has square blades but works great. $100 shipped.
Mark

old68

good point , maybe the 5 is fine, and just fix the clutch, it pulls pretty good now

Frankie the Fink

I run a 7 blade fan as Mark shows above along with the Hayden 2747 heavy duty (truck) clutch. It engages sooner and at a greater percentage of full RPM... My 63 cruises all day at 175* in Orlando summers with the A/C on...

59BlueSilver

I probably took my cue from Frankie because I'm running a 7 blade with a 2747 clutch. Had overheating problems before. Not now.

larrywalk

Dang! If I had removed my 7-blade fan, I might have gone even faster when I set the NCCC 2B drag record!

Gary's '66

Maybe so Larry. Try it on your next run.

Kidding aside, I think the other part of the equation came from the fact that I was also running a heavy duty fan clutch which locked up earlier. All I can say is that there was a very noticeable loss in power.

old68, if you do stick with a 5 blade but want a bit more pull through the radiator try an a/c fan which has more pitch.

Gary

Westlotorn

7 blade vs 5 blade, a 7 blade will be louder when engaged. But it should not engage any time that you are not running hotter than your thermostat. Normally they will kick in around 200-210 at your gauge temp. I would prefer a 7 blade it will pull more air and cool you faster. A five blade in same situation may not pull enough air and your temp will run higher than it would with a 7 blade. All other things being equal.
A fan clutch will also normally engage briefly after the car has been parked, cold start.
The fluid remaining in the clutch area ( silicone ) will settle to the bottom of the clutch and cause temporary lock up on cold start. This is supposed to disengage in 20 to 45 seconds after cold start and and quiet down.
I replaced the fan clutch on my Suburban a while back when I replaced the water pump.
Installed a heavy duty Hayden clutch. It worked just fine but it took almost 4 minutes to disengage on cold start and the noise drove me nuts. It was very loud with every cold start and the colder it was the longer it took to disengage.
I put the OEM Eaton fan clutch on and it worked exactly like the factory clutch, worked when needed and was quiet all other times. The Hayden Heavy duty I purchased was too aggressive for me on that application.

Engaged a fan clutch should spin your fan blade 90% of engine speed so it will howl when fully engaged. When disengaged they should only spin the fan blade 10% of engine speed (Hayden clutches say 25-30% disengaged) so they run quietly and efficiently. In the 80's I worked for Kool Klutch and they advertised the 90/10 number. Hayden has since purchased Kool Klutch so I have no current numbers.
Disengaged it should not matter if it is 5 or 7 blades they should both be quiet and waste little power.
If you are feeling a power loss your fan clutch is not engaging properly and it is wasting power. The only way it can do that is if it is engaging when not needed for cooling.

I have not looked in over 10 years but Hayden, Kool Klutch, Eaglemotive, DeRale, 4 Seasons, Delco all sold fan clutches and you could look up the applications on line and find the temp they are supposed to engage at. This temp is at the fan clutch and this number is usually 30 degree's cooler than the radiator temp. So if you want a clutch to engage when your engine hits 200 you buy a clutch to engage at 170. The numbers I quote are for passenger cars and trucks. In these Vettes with a much larger than normal area from the radiator to the fan clutch and the radiator sitting at an angle they may have a different adjustment number. Anyone have any information on the Vette C2 target temp at the fan clutch for the clutch engagement? I bet Hayden would have a tech line that could answer this. It would not surprise me that the Vette spring engages at a cooler temp than other passenger cars and light trucks just due to the odd angled layout of the radiator in the C2 and C3.
This could be the reason so many owners install a new clutch and it never engages. It might have the wrong engagement spring for a Vette Application.

Frankie the Fink

Even though this doesn't cover the Eaton or Schwitzer fan clutches used on our cars; it does give an indication of "normal" vs "heavy duty" difference within a single manufacturer (Hayden)...one item of note is that the clutches are designed to work with fan blades of different pitch -- you don't see that discussed much here.

There is also a fan clutch rebuilder that says reclocking the front spring (supposedly to reduce the temp when the clutch engages) is a bogus exercise. Many here have done it. Myth #6:
http://www.pamperedcorvettes.com/Pam...tes/Myths.html

split1963

Please confirm the HAYDEN 2747 clutch has a short shaft for BB or longer shaft for SBC my issue is I would like to go to a HD fan Clutch but order oned that came in with a short shaft that is not only 1/4" in the shroud need to confirm that the 2747 is longer and will push the fan into the shroud deeper I can't seem to locate the distance and all the pictures are not always correct

Frankie the Fink

Part way into this document are ALL the relevant specs for the Hayden fan clutches -- the 2747 specs are in there as well; if you have a BB you may require a different heavy duty version of their products:

split1963

the confusing part of the schematic the the E distance on the standard the distance measured is from the outer flange to the top of the clutch on the heavy Duty one the "E" distance is from the outer flange to the inner flange of the clutch not the outer so I can't really tell the size of the shaft, is it the correct SBC long shaft that I need

split1963

did some more research used Rock Auto which is where I ordered my previous fan clutch they claim that 2411 is both for BB and SB but that is incorrect the SB has the a longer snout the 2411 "E" distance is 1.40 was looking to get the 2747 which is 1.625 but now realized that the 2747 will not fit my Fan because the correct bolt pattern for the fan is 3.00 and the 2747 is 3.25. this is getting really freaking outrageous. HELP lol need a HD clutch fan with at least 2" snout "E" distance and 3.00 fan pattern "F" distance

fjd

Frankie can u point me to fan clutch replacement instructions on here, I recall a few thinks like keeping one bolt on or something so the thing doesnt fall off. Cant find any of it now that I need it.

Much obliged!
Frank

Frankie the Fink

An old thread, but anyway, I just take the four bolts out without disturbing ANYTHING else and remove the fan and clutch in one assembly. You may have to hold the fan blades with a glove or wedge a screwdriver or ratchet extension against the other bolts to get an individual bolt un-tightened (loosen them all before removing any) and there may be a bushing on the nose of the water pump flange as a spacer and generally the fan belt tension keeps the water pump pulley on; the pulley may tilt slightly but will straighten up when the parts are reassembled.

I reinstall the ***'y by reversing the process...and do a final check of fan belt tension...
If you can depress the fan belt about 1/2" with a thumb along its longest stretch between pulleys then its fine.

You can separate the fan and clutch on the workbench.. This may not be kosher with everybody but I'm lazy and this works for me...

This is on my 327 ci small block 63 without A/C...

I don't recall anything about leaving one bolt on..

fjd

Frankie

Thanks. The temp has crept up 10 degrees lately which is odd. I know the clutch wont solve that. I have good pressure, new harrison tank, radiator "seems" OK. It was replaced about 10 years ago. Not much mileage but a lot of years. Thermostat is new, antifreeze new. Shroud OK.

I just did new wiring harnesses, not sure why that would matter. Infrared gun seems to confirm gauge temp. I was going to put on a 6 blade fan for now. Figured when I do so, I should change the clutch. I have no idea how old the clutch is. The thermostat was a pile of junk when I swapped that out last summer. A radiator may be in the future but Im trying to put that off. If she can run all day at 190 that's OK. I just spent a fortune on suspension, new shocks and brakes. Went with the Bilsteins and love em.

Thoughts?

Thanks
Frank

Frankie the Fink

Might just be time for a new chemical flush and even better if you can remove the block drains; I would do that before swapping other parts onto the car... Could be time for a new radiator cap as well and make sure the bottom radiator hose has a spring in it and is not collapsing....

I do run a BB fan with a heavy duty Hayden 2747 fan clutch, but only because I added A/C and I simply hate electric fans, the look and the complexity. THAT setup is on the left, original 63 setup is on the right....

I also added the rubber "gap flap" found on 67 A/C cars...it'll fit other years with a bit of trimming and directs air flow more concisely; many vendors sell them....Dr Rebuild has the most faithfully formed reproduction: