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The Wild World Of The Small-Block Pumps, Pulleys, And Brackets

Jeff Smith Feb 1, 2001 0 Comment(s)

Step By Step

This is a typical short water-pump accessory drive setup that includes the alternator mounted off the exhaust on the driver side, a power-steering pump mounted low on the driver side, and the A/C pump on the passenger side. This bracket system comes from Vintage Air.

In 1969, Chevy converted to a long water pump that demands different pulleys and accessory drive mounts. The most typical long water-pump setup mounts the alternator on the passenger side. Power steering still sits on the driver side, with A/C mounted now on the driver side.

This comparison of the long water pump (left) versus the short water pump (right) reveals the height difference.

The short water-pump GM reference height from the block mounting flange to the pulley mounting flange is 5-5/8 inches. The long water-pump reference height is 7 inches. To make this even more confusing, Chevy also used late-model serpentine-belt short water pumps, but these use a 5-13/16-inch (5.8125-inch) reference height for ’84-’92 Corvettes. There is actually yet another reverse-rotation water pump used in serpentine-belt applications for ’87-’94 small-blocks and 90-degree 4.3L V-6 engines that uses a 6-15/16-inch reference height. Whew!

The biggest hassle with aftermarket pumps, pulleys, and brackets is that this reference height can vary dramatically. This photo shows two aftermarket short water pumps with a 3/8-inch difference in height. This is often what causes pulley misalignment. We’ve found that most good aftermarket pumps like the Edelbrock, Weiand, and Stewart pumps are very close to the factory reference height. However, inexpensive iron rebuilt pumps you get from the local auto parts store are often way off.

The best way to align all your pulleys is to use a quality pump. If that’s not possible, Mr. Gasket, Canton Racing, and others sell these aluminum water-pump and crank-pulley shims that will space out either pulley to create the proper alignment. You could also make your own.

It’s important to emphasize that when you’re in the middle of mixing and matching pulleys, it’s easy to get mixed up. Multigroove short water-pump crank pulleys might look like they will work with a long water pump, but they won’t. You cannot interchange short and long water-pump pulleys without causing all kinds of headaches for yourself.

The biggest pain for short–water-pump accessory drive users comes if you are using early-model production iron heads with no accessory bolt holes. This requires using a header mount for the alternator. Unfortunately, those standard alternator mounts are very flimsy and often break. This mount from Tim Moore Automotive is made from 1/4-inch plate and is extremely durable. Tim can also mount the alternator on the passenger side as well.

This is a shot of a typical serpentine belt-drive setup on a late-model TPI Camaro engine that requires the use of a reverse-rotation water pump because of the belt routing. The Corvette accessory-drive layout is different, but still requires the use of a reverse-rotation water pump.

For a short three-year period, Corvette mounted the alternator on the passenger side from ’63-’65 using a short water pump. We’ve included this only as an option if packaging gets tight on the driver side. This would require moving your alternator charging wiring, however.

An interesting option is to use a Chevy truck bracket that uses accessory bolt holes in the cylinder heads to mount the alternator in close to the long water pump. This was also a Corvette application from ’73-’81.

March Performance makes several examples of serpentine belt drives for a standard-rotation long water-pump setup both with...

...and without power steering.

This is a most confusing story about perhaps one of the simplest systems on an engine. OK, so maybe this isn’t the simplest system on a car, but it sure looks that way. We’re talking about the world of water pumps, alternators, power steering, and A/C compressor pumps.

This story will outline the three basic systems that Chevrolet has used to drive the pumps, belts, and pulleys throughout the most popular 35 years of the small-block. We’re not going to deal with the generator years of ’55 through ’61, nor will we touch on the LT1/LT4 or LS1 engines. Frankly, there’s plenty to get confused about without going into the newer engines. As for big-blocks, if we have any sanity left once we’ve completed this series, we might just be dumb enough to take on the fat-blocks. This will greatly depend upon how much feedback we get on this series from our very astute readers (that would be you).

So here goes. We’ve broken the small-block accessory drives down into three categories. Group 1 will deal with short water-pump accessory drives with no accessory bolt holes in the cylinder heads, which is the early factory setup from ’62 to ’68. The largest section, Group 2, will cover long water-pump drives with accessory bolt holes in the heads, which runs from ’69 to ’86. Group 3 will cover serpentine belt drives that started around 1987.

Group 1 is the oldest group, but there are literally dozens of variations on this theme. The simplest version is an alternator drive located on the driver side (left) of the engine mounted off the cast-iron exhaust manifold. This started in 1962 with the use of the Delco external regulator alternator. Other accessories included a power-steering pump that was also located on the driver side, down low near the crank pulley. This necessitated a dual-groove crank pulley. Air-conditioned cars located the A/C compressor on the passenger side with brackets that located off the water pump and exhaust manifold with braces off the intake manifold. These large compressors needed all this bracketry in order to solidly mount the unwieldy pump and also demanded a triple-groove crank pulley.

Corvette applications were slightly different for several reasons. Corvette kept the short water pumps but used a larger ¾-inch pilot shaft (standard is 5/8 inch), which is the diameter of the small snout that locates the water-pump pulley. Most V-belt Corvette drives mounted the alternator on the driver side except for the first three years of alternator use. Brackets and pulleys can be interchanged from the Corvette, but we’ll focus mostly on passenger cars since these parts are easier to find.

The big change in 1969 was the move to the long water pump. This required a complete change in accessory drive pulleys, brackets, and even the positioning of the accessories. The biggest change that accompanied long water pumps was moving the alternator to the passenger side of the engine. This placed the alternator closer to the battery, but also required moving the A/C compressor to the driver side. The power-steering pump remained on the left side. Accessory bolt holes also appeared in the front of both cylinder heads.

While this sounds simple, there are several different factory alternator and power-steering mounts depending upon the vehicle and year application. This long water-pump V-belt setup ran from 1969 to well into the mid-’80s, with various water-pump mount layouts, different power-steering pumps, and alternator changes as well. This makes this group design the most complicated. If you are junkyard-searching, the best approach is to buy all the brackets for all the accessories along with the pulleys. This way, you’re guaranteed that all the pieces will cooperate.

The aftermarket covers this group extensively. There are two major long water-pump alternator-mount setups that are the most popular. While some of the pieces may interchange, the best way to approach this is to purchase an entire package of mounts that are designed to work together. We’ll cover this area in more detail in part three of this series.

According to our sources, Chevy first used the dedicated serpentine belt system in the Corvette in 1984, and the Camaro followed suit in 1987 and 1988 for serpentine belt use in the Tuned Port V-8s. We’ve placed all of the serpentine belt-drive setups into Group 3 along with the little-known 4.3L V-6 used in the S-10 truck. Since the 4.3 is a 90-degree V-6 that is basically a Mouse motor with two cylinders removed, a serpentine belt setup for this engine can be used on a small-block. However, you will need to use a reverse-rotation water pump, and accessory bolt holes must be in the correct location in the heads. There were also some strange applications that employed a combination of V- and serpentine belts to drive all the accessories.

The factory serpentine systems are best used as a dedicated system that include the late-model alternator mounted on the passenger side, a power-steering pump, and A/C mounted on the driver’s side. Corvette and Camaro accessory drives are different, so if you are looking for a specific drive system, you should investigate both. On the aftermarket side, the variations are almost infinite. Companies like Arizona Speed & Marine, March, Zoops, and others offer serpentine belt systems that can be grouped into two categories using either a standard or reverse-rotation water pump.

As you can see, there are a ton of variables here when it comes to just the small-block Chevy. This story is intended to give you an overview of all the different variations on the accessory-drive theme that Chevrolet has pulled off in the last 40 years. If you are thinking of a whole new drive system for your small-block, the best choice is probably a long water-pump setup using heads with accessory bolt holes since this offers the most choices and the most opportunities to fit everything. The advantage of the short water-pump system is its ability to fit into tight- clearance applications.

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