Thread: Smaller Crank Pulley - Good Idea or Not

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Am building a chevy 350 for street use to be put in an 84 camaro (with all acc'y, even a/c).

Was considering one of those smaller (underdrive?) crank pulleys - I know I willl get more HP to the ground, but I was wondering if and what the negative side effects might be?

Anyone run one of these and tell me if the batt stays charged and if the car runs hot?

thanks
chris

I don't think you get enough horse power benefit to justify the expense. The factory engineers size the pullys a tad larger than necessary. This ensures that the accessories, and the water pump in particular, spin at the rate needed to function properly under all conditions. Call it a safety margin. Smaller crank pulleys work by taking some of this safety margin away. You may not have a problem. But then again? I like the pulleys that GM Performance offers. They are well made, affordable, and as small as the factory engineers are willing to go. Some (most/all?) of the off shore chrome pulleys are junk and the machined billet jobs can wear faster than steel.

I agree with Bib_Overalls. If by street use you mean you are going to really be driving a lot. I watched (during the 80's when I lived in the Chicago burbs) a lot of fellow 5.0 Mustanger's use the power pulleys, and believe me when they got caught in a traffic jam they couldn't keep them from overheating.

On the street ya need stock diameter pulleys...

OK, stock it will be.

thanks
chris

Mine had an eight inch pulley and whenever I punched it, I would lose a belt.

Then I went to the serpentine system, but there too, I would lose the belt.

So, I switched to a four inch crank pulley and no more belt jumping. Now when I come to a light, the amp gauge shows a discharge situation, however it more than compensates for the belt jumping I used to experience.

As for over heating, no problem, but then I have dual electric fans. If I had a pulley driven fan, it probably would heat up. But I have found that the water pump turns fast enough even now.

I don't know if a six inch pulley is available, but that might be the answer in our case.