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Water Pump Underdrive Pulley

Pulleys & Belts - Water Pump Underdrive Pulley
Pulleys & Belts - Water Pump Underdrive Pulley

Dyno testing our 5.5" underdrive pulley on a near stock L36 showed 3WHP gained at 6k rpm. In car testing shows only a 2 deg increase in operating temps over stock. Higher gains are possible depending on your engine combination. Pulleys are available in a high gloss black anodized finish.

  • 8% underdriven
  • dyno proven horsepower
  • lightweight design saves a pound of rotating mass
  • increases water pump life expectancy
  • better fuel economy

One size larger than stock belt recommended.

Does NOT fit HBody cars because of their front engine mount. Bonneville, Park Ave, & LaSabre.


Water pump pulley: 115 in/lbs.

Pulleys & Belts - Water Pump Underdrive Pulley
Pulleys & Belts - Water Pump Underdrive Pulley
Customer Reviews
4.8 Based on 13 Reviews
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Antone J.
United States
Underdrive pulley

it fit good an very light compared to the oem

Joshua T.
Easy first mod

Easy install for quick gain in hp I’d recommend a lower degree thermostat and make sure you order the proper belt size

Osiel J.
Pulley slaps right in a

Pulley slaps right in a lot lighter then OEM product. Noticed different idle and faster throttle response would definitely recommend one of these bad boys

David S.
Underdrive water pump pulley

Very light weight when compared to stock pulley! Only needed to go 1/2 inch bigger in belt size. Idle has improved as well as revs and slight pull when accelerating. Didn’t get 5*s because it had some couple jagged edges where the belt lays that needed to be ground down, but it a very nice item.

Jason N.
Water pump under drive pulley

Great product light weight. The car response is much better now. A mod that truly works and only takes 15 mins to install. Didn't notice a increase in temp at all.