HELP! Fan belt too big on 1937 Cadillac

[boothandco]

I am just finishing a swap (rebuilt 1946 346 ci for  the original1937 motor).  Pulled pulleys off of old engine put them in New engine.  Bought brand new Gates belt (42 7/8 inch x 1"). It is what is called for on that car according to Gates..  It is too big.  If I take out all the tension I hit the generator and belt is still to loose.  Looks like the belt is 2 inches too long at least.  Could the pills on the motor be the wrong size?  Can anyone help I want to get this car running again.

[Steve Passmore]

This has been discussed many times on this forum. There is no set belt size for all the flatheads because there are variables. From all the engines I have dismantled (36 through 48) I have seen 3 different sizes of fan bracket. Who's to say you have the correct one?  Your 37 engine actually took a wider belt than 1" so the later 1" belt is probably sitting too low in the pulleys causing it to be too long.
Best thing to do if you know it's 2" too long is to get a smaller one at 40" maybe?
Great fun these cars eh?

[DaveZ]

If you put a 37 water pump on it the pulley for 37 is smaller then the water pump pulley on the later year cars. Do what Steve said and get a smaller one until you get the right fit:-) My 37 is smaller then our 40.
Best wishes.