Here at Butler Performance, we get a lot of tech questions. Some of the most common questions regard cooling the Pontiac engines and water pumps. We have taken some time to show the difference in the water pumps and help you with conversions as well. Let us start with the water pumps themselves.


Pontiac Water Pumps

There were two style water pumps made for most Pontiacs. 8 bolt (1968 and earlier) and 11 bolt (1969 and later). Many early model Pontiacs with the 8 bolt style seem to have cooling issues. The cooling seemed much improved on the 1969 and later models. Many people convert their 1968 and earlier 8 bolt water pumps to the later model 11 bolt style. To do this, it takes a replacement 11 bolt timing cover, water pump plates, sleeves, and the 11 bolt water pump. This is a pretty easy change. There is also a difference in impellers.


Water Pump Impellers

Many aftermarket OEM style water pumps come with stamped impellers as seen in the image. The factory water pumps came with a cast impeller and some replacement water pumps feature these as well. The high volume pumps such as the Flowkooler, come with an engineered impeller machined from aluminum.


Water Pump Impeller Clearance

Why does the impeller matter? The image shows how much clearance there is between the water pump plate and the impeller. The less space you have without interference means the water will be better directed. This will improve the flow and circulation.


Measuring Water Pumps

This image shows how to measure the Pontiac Water Pumps. The measurement is taken from the back of the pump to the face of the hub as shown in the picture. Using a flat object, place it against the face of the hub of the water pump as shown. Measure from that point to the rear of the water pump. This will give you the correct length (or some call it height) for the water pump you need.

The early 1969 water pump was 11 bolt and measures 4". In mid-1969, Pontiac changed to a 4.5" water pump. If you do not have the 4.5" model water pump or opt to upgrade to a high flow water pump, which measures 4.5", you will need to replace your pulley as well.

We stock kits with everything you need to make the change. No matter if it's simply a water pump upgrade, change from the 4" to a high flow water pump and need the pulley, or you decide to upgrade from the 8 bolt, we have replacement timing covers, plates, sleeves, high flow water pump, and pulley kits to meet your needs. Click here to check out our water pumps, kits, conversion kits, and more here.