68 327 water pump belt ?

[greggome]

I just put on a new water pump belt. My old brittle one from 20 years ago that i just pulled off has a Gate # of 7325 which Gate tells me they have the same belt # now as well (and is listed as the replacement # for the original GM part). I measure both belts and they are very close but the new one comes out about 1/16" longer (I figured this might be due to my old belt having some shrinkage). I have installed the new one, and since there is no tension adjustment on the 68' it has to fit correct. The belt seems a bit lose to me. With the alternator belt off I can rotate the fan/pulley assembly with my hand. The belt offers some resistance but does not prevent me from turning the water pump pulley assembly without the belt moving with it. (of course the lower crank shaft pulley does not move during this so the belt just slips on the upper water pump pulley.) I am concerned this is not a proper fit but this is the belt size 33 1/8" that references with the GM #3935420. Anyone have experience with this and the proper belt tension?

 

[bill81vette]

1st Welcome to CAC!!!
hope you enjoy the forums!!!

now,have you started the vette to see if its runs around the pulleys smoothly,and not screeching.....
that's about the only way I know of to tell if a belt is working properly.

 

[greggome]

Not yet. The car has not been run in many years and I am in the process of replacing all old hoses and belts etc. before the start up. I have hunted around but cant find any belts that are slightly smaller so i guess I'll have to go with the looser belt and hope it works out.

 

[kpic]

I used to design engines and have the formula to calculate belt lengths.

Sort of a blah-blah exercise done by the engine designers which holds little interest if all you want is to a belt which works.

Belts - Length and Speed of Belt

This one mentions pitch diameter or an imaginary line where the belt contacts the pulley.
Flat Belt Length Distance Calculator - Engineers Edge Engineering Calculators

The above states flat but at the site it says Flat or Vee.

The manufacturers of the belt and pulleys provide a gage or pitch diameter for both. The center distance and range of adjustment is done by Engine Design. The belt manufacturer also provides the maximum stretch.

However with some measuring, the above will get you a lot closer than a slipping belt. Try to center the bolt in the adjuster so you have adjustment for when the belt stretches.

Good luck and if you need a hand the CAC crew are here.

 

[greggome]

Thanks for the information!