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Video: Choosing a Water Pump for a Small Block, Big Block Chevy V8 Engine

 

Learn how measuring your water pump from the mounting flange to the hub surface of the pump can tell you what kind of pump is currently installed in your vehicle, and why you need to pay attention to snout diameter when choosing a new or replacement water pump for your engine.

Hi I’m Mike and on this installment of Summit Racing Quick Flicks we are going to talk about the differences between Chevy V8 water pumps.

One of the questions we commonly get is what water pump is right for my Chevy V8, whether it be a small block or big block Chevy. The reason for this is Chevy developed two different types of water pumps for these engines: a short-type and a long-type. By physically looking at these pumps when they are mounted on the engine, it is difficult to tell which version you have on your engine. So today we are going to discuss the differences between the pumps and how to determine which pump you actually have installed on your engine.  So, when you actually go to replace this pump, you will order the correct one.

So how do you go about determining which version you have on your engine? Well, usually I will just take a tape measure and take a measurement from the mounting flange to the hub surface of the pump. Your typical long-version pump will be six and seven-eighth inches tall from that flange to the hub surface. In comparison, your short pump will be roughly five and five-eighths from the mounting service to the hub surface. Now there was a year split between the years in which these pumps were used. The short pump was used most commonly on 1968 and earlier applications, and the long pump was used on 1969 and later applications. The thing about this is you cannot guarantee the one or the other is going to hold true to your specific vehicle. The reason being is a lot of engine swaps have happened over the years where they have taken complete engines, including the accessory drives and all of the components that go with that, and swapped them into early model vehicles or vice versa. So it’s really best to confirm which version is on your application via taking a measurement or physically looking at the pump and determining which one your vehicle has on it. 

Now the one exception to the year break rule is the Corvette. Corvette applications held on to the short-type water pump for a much longer period. In fact, it carried on to the point which they quit using belt driven water pumps. In those cases, it is not really possible to switch to a long pump in a Corvette application because of radiator clearance issues. The radiator is a lot closer the engine in a Corvette in comparison to your standard Camaro or truck application. So make sure if you do have a Corvette and are doing an engine swap that you go ahead and swap over the proper accessories as well from the original motor, because if you don’t, the long water pump that is on that later model motor may not work with that engine compartment set up.

The last thing you need to consider before selecting the proper pump for your application is your snout diameter. This right here–the snout–can affect the way your pulleys fit as well as the way your fan assembly fits. GM used two different versions. They used five-eighths, which is the most common, and they also used the heavy-duty version which is three-quarters  of an inch. Make sure you confirm which one your vehicle had before selecting the proper pump for your vehicle.

There is another way you can determine which pump you have just by taking a visual inspection of the engine. You can see here how the gap in between the pump and the block is very narrow. This typically indicates that you have a short-type pump on your engine assembly in comparison on a long water pump application. There will be a much larger gap between the pump and the block assembly to the extent you can almost fit your hand in-between the two. 

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