What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

Shimming out Fan Blade/Clutch

Justin Fleming

Justin Fleming

1/2 ton status
 Premium
Joined
Aug 24, 2005
Posts
924
Reaction score
48
Location
Oxford MI
What is your guys take on shimming out a fan blade on a water pump 1 1/2" to get the optimal fan location? On our race cars we did this 2+" running 8k rpms all the time with out any problems. The only difference is we did not have the fan clutch added weight.
 
I would suggest getting a fan clutch with the dimensions you need rather than adding a spacer. I have called Hayden and flex a lite in the past and had them look up numbers for me by dimension when doing customer cars
 
My guess is something like a small block motor and a big block shroud so it doesn't "reach" deep enough in to the opening?
 
yes to the small block/big block fan shroud. I will call those folks today and see what the part numbers might be for a different fan clutch with longer reach. The other option is to add a collar to the fan shroud which is not much of a big deal
 
I would think shimming the clutch that much would cause repetitive water pump failures.

Maybe space the whole shroud out towards the motor? You could use spacers at the mounting points and then a semi-soft rubber flap around the perimeter to seal the gap. The shroud on my Cummins has a soft layer like this.
 
I put a 2" fan spacer on a 400 small block in the '77 GMC K2500 I had,the truck had a 3" body lift and the fan shroud was cut away to compensate,and I had overheating issues--I figured the fan needed to be closer to the radiator and deeper in the shroud ,so I added the spacer,using longer bolts..

Well,it was OK until one day we had a deep snowfall,and while I was plowing my driveway,I had to batter-ram the snow to get it to move,and I ended up going over center on a snow bank,and I tried rocking the truck from forward to reverse to get it un-stuck..
I red-lined the engine a few times,and then I heard a loud "BANG",and saw steam,so I shut it down..
I thought it threw a rod!..:eek:

Turned out the water pump impeller shaft sheared off flush with the casting,and the fan & clutch spun off at high RPMs and scarred the radiator up,and chopped the upper hose off at the inlet fitting on the radiator,it mashed the fitting almost shut..:yikes:..

I had the fan clutch "locked" to get maximum air flow to prevent overheating when I had the plow on the truck--that may have been the cause,the extra load may have been too much for the water pump shaft..(I had discovered the engine had no thermostat in it,and installing a 195 thermostat and locking the fan clutch ended the overheating issues)..

When I put a rebuilt water pump on it I decided to leave the spacer out,and ran it with the fan clutch bolted directly to the pump...the engine never overheated with the plow on as long as the clutch was locked in the "on" position,despite it not being in the shroud hardly at all..

I don't think I'd trust a spacer with a fan clutch after that experience..
I was lucky I was able to solder the radiator hose inlet back in after forcing it round again,and it only cost me an upper hose,water pump,and two new v belts to get it running again..(it also put the truck out of commission,with the driveway only plowed about 3/4 of the way to the street,with a huge mound at the street left by the DPW plows..

I had my father's Dodge Airies nearly airborne to crash thru that snow bank,to get to a parts store to buy the parts to fix the truck,I had to back up ,get running start,pray no cars were coming,and floor it and hang on..then make a 90 degree tight turn to get on the street!..
Had to shovel a path wide enough to fit the car thru when I got home..and had to use a winch and 50 feet of chain to drag my truck out of the snowbank..real sucky day..took all day to get the truck to the garage..:(
 
There could be a water pump with a longer snout for another application, but you'd need a deeper pulley to go with it.
 
You must log in or register to reply here.

Latest Posts

Top Bottom