My water pump pulley bolt holes don’t line up (small block Ford)
Water Pumps and Cooling
Everything else in the kit bolts up, but the water pump pulley holes are spaced wrong. On small block Ford this is almost always a rotation question rather than a fitment problem.
Overview
Short Answer
On small block Ford, 289, 302 and 351W, standard rotation and reverse rotation water pumps use different flange bolt circles. Standard rotation is 1.75 inches, reverse rotation is approximately 2.06 inches. If your pulley will not line up, check which flange your pump has before anything else.
The two bolt circles
This is a small block Ford issue. Ford ran both rotations across the 289, 302 and 351W family, and the two use different flange bolt circles. If the holes in your flange sit further apart than the holes in the pulley, you are almost certainly looking at a reverse rotation flange against a standard rotation pulley, or the other way around.
| Flange type | Bolt circle |
|---|---|
| Standard rotation | 1.75″ |
| Reverse rotation | approximately 2.06″ |
Measure yours across the centres of two opposite holes. Our pulleys are machined for one bolt circle, matched to the rotation the kit is built around, so the two have to agree.
Your two options
Fit a pump with the flange that matches your kit. This is the cleaner route and keeps everything as designed.
Drill the other bolt circle into the pulley yourself, if you would rather keep the pump you have.
Check the bigger picture first
A bolt circle mismatch often means the pump itself is wrong for the system. If you are running a reverse rotation flange on a V-belt setup, or a standard rotation pump on a serpentine setup, you have a rotation problem as well as a bolt hole problem. See our article on overheating after a serpentine conversion before you drill anything.
Not sure what you have?
Send us a photo of the pump flange with a tape measure across it, plus your order number. We will tell you which one you are looking at.
Still need help? Our tech support team can get you pointed in the right direction.
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