Early Corvette Water Pumps

Top pump is built in Tonawanda, bottom pump is Flint built. Pointer shows lack of reinforcement ribs on Flint water pump.

 

Author: Alan L. Colvin

 

The standard Chevrolet waterpump is simply a cast iron pulley-driven pump, which is bolted to the front of a Chevrolet engine. This pump serves the function of forcing water and coolant through the engine, primarily the block, to cool the engine. As simple as this may sound, complications can arise when someone wants to restore their car and they want an original waterpump casting number and corresponding dates to match their engine.

 

In this edition of Chevy Classics, we are pleased to present updated information to an earlier (August 1992) article on Chevrolet waterpumps that ran in another national publication. As we requested in that article, several readers called and sent letters concerning new waterpump information. These responses resulted in a review of the documentation that was used to prepare that article. After several phone calls to our sources inside General Motors, we began to see a different pattern of information developing. Bill Mock of Bartlesville, Oklahoma, who has been supplying original waterpumps to the Corvette restoration industry for many years, was also contacted to help us piece the information together. The new General Motors information that we acquired was then cross-referenced into Bill Mock's application index. Bill has been compiling this index for the last twenty years. By utilizing these two sources, we feel confident that we now have the casting information correct.

 

There is great difficulty in assigning the absolute correct applications of water pumps installed on Corvettes from 1955 through 1982. One reason lies simply in the great variety of water pump configurations used. A second reason is that water pumps with the same design were often produced concurrently by different manufacturers, but with different casting numbers. The last and most puzzling piece of the applications puzzle is due to water pump rebuilders who altered original design features to enable a manufacturer to use a water pump on additional applications. On top of all this, water pumps are an often-replaced part. The water pump on any particular engine is as likely as not to be a replacement part, so you can see how the problem of researching and validating original casting numbers to specific models and years is very difficult. It should be noted that original 1955-60 water pumps had a flat plate on the backside of the pump, which was secured by six slotted pan-head screws.

 

There were two distinct water pump designs used on Chevrolet passenger cars and Corvettes between 1955-1959, the first from Flint, Michigan, and the second from Tonawanda, New York. From a restoration viewpoint, you should know that Flint engines were supplied with Flint water pumps and Tonawanda engines with Tonawanda pumps. The design differences between the two pumps are very easy to spot and can be a good indicator of an incorrectly restored engine. Corvette engines always used the Flint assembled waterpump.

 

This photo depicts the casting date "E2060" number location inside the ribbing of the Tonawanda waterpump. The date code "E2060" depicts a May 20, 1960 date that the pump was cast.

 

The first difference is that Tonawanda water pumps have external ribs or ridges, while Flint water pumps do not. Also, note that Tonawanda pumps have a cast “T” on them and that on Tonawanda water pumps the casting date is visible when the pump is installed on the engine. On Flint pumps, the casting date (if applicable) cannot be seen with the pump installed.

 

There are two basic styles of water pumps installed on these cars, the “short leg” pump and the “long leg” pump. Application of each style depends on model and year, but generally, the short leg was an earlier design and the long leg a later design. In the following text and casting number breakdowns, please realize that this is a very reliable, but probably not perfect, chapter. Because of the complexity of this chapter, each specific engine family is listed separately and the verified casting numbers are listed chronologically.

 

Short leg style water pump (right) as compared to the long leg style water pump (left).Long leg water pump was introduced on most Chevrolet models while the Corvette did not change water pump styles until 1971.

 

Many of the early water pumps covered in this book do not carry a casting date. Please refer to the specific features given and the chart below to identify the pump you are searching for. Where dating of water pumps is known, it is noted in the application table. (Truck water pumps have dates and can be identified by the two reinforcement webs on the pump.)

Where casting date codes are present, they follow the same pattern as engine blocks, but some do not carry the year. The month code is always a letter, followed by a number signifying the day. The last number signifies the year of production.W-block water pumps (as well as big-block pumps beginning in 1970) used a two-digit year code.

 

Water Pump Month Codes (1st Letter)

A - January E – May I - September
B - February F – June J - October
C - March G – July K - November
D - April H – August L - December

Example: Date code B 18 9 (Flint small block)

  • B = Month: February
  • 18 = Casting date: 18th
  • 9 = Calendar Year: 1959 (refer to casting number charts to confirm)

 

Example: Date code B 18 59 (Tonawanda small block and Passenger Car W-block)

  • B = Month: February
  • 18 = Casting date: 18th
  • 59 = Calendar Year: 1959

2. SMALL BLOCK WATER PUMPS

Small block Chevrolet engines used the “short leg” water pump on passenger cars through 1968 and on all Corvettes. Along with casting number changes through the years, there were also design changes due to the addition or deletion of accessory brackets. Note that a casting number of water pump overlap has not been verified. 

Pump #3704911

Year Application Engine Horsepower
1955* Corvette 265 195
1956** Corvette 265 210, 225, 240
Note: The only difference between Tonawanda and Flint #3704911 pumps is the cast “T” on Tonawanda pumps.
*No 1955 pumps have a boss.
**Has flat boss on top of pump. No dates

 

Pump #3736493

Year Application Engine Horsepower
1957 Corvette* 283 220, 245, 250, 270, 283
1958 Corvette* 283 230, 245, 250, 270, 290
1959 Corvette* 283 230, 245, 250, 270, 290
This was the first Tonawanda water pump that had “ribs”, and differed from Flint pumps in this way. Later pumps followed the same pattern.
*Uses special Corvette front engine mounting bracket. This pump was also used in 1960. No dates

 

Pump #3736493

Year Application Engine Horsepower
1960 (flat boss on pump top) Corvette* 283 230, 245, 250, 270, 290
*Uses special Corvette front engine mounting bracket
No dates

 

Pump #3782608

Year Application Engine Horsepower
1963 Corvette 327 250, 300
1964 Corvette 327 250, 300
*Service conversion only - Pump dates start March 1964
1965 Corvette 327 250, 300
1966 Corvette 327 300
1967 Corvette 327 300
1968 Corvette 327 300, 350
1969 Corvette 350 300, 350
1970 Corvette 350 300, 350 A/C, 350 w/o A/C, 370

 

Pump #3782609

Year Application Engine Horsepower
1961 (bypass hole on top of pump) Corvette* 283 230, 245, 270, 275, 315
1962 Corvette* 327 250, 300, 340, 360
1963 Corvette** 327 340, 360
*Uses special Corvette front engine mounting bracket
**The changeover date to #3859326 casting number is still being researched. Flint Engine Plant build records show #3782609 in production in 1/4/63.
No dates

 

Pump #3839175

Year

Application

Engine

Horsepower

1963(Late) (Small bypass hole on top of pump)

Corvette

327

340, 360

1964

Corvette

327

365, 375

This water pump was used randomly in late 1963 and 1964 Corvette high performance engines. The reason for this is unknown and is still being researched.

No dates

 

Pump #3859326

Year

Application

Engine

Horsepower

1963 (Small bypass hole on pump top)

Corvette

327

340, 360

1964

Corvette

327

365, 375

Dates start November 1965

 

Pump #3859326

Year

Application

Engine

Horsepower

1965

Corvette

327

350, 365, 375 (Small bypass hole on top of pump)

1966

Corvette

327

350

1967

Corvette

327

350

Date codes on the #3859326 water pump start in November 1965.

 

Pump #3927170

Year

Application

Engine

Horsepower

1969-71

All cars

_

_

 

  • In 1969, the water pump design changed from a “short leg” design to a “long leg” design, excluding the Corvette which changed in 1971.
  • This water pump was used interchangeably with #3953692. #3953692 saw extensive usage. #3927170 saw very little usage.

Pump #3991399 

Year

Application

Engine

Horsepower

1971

Corvette

350

270, 330

1972

Corvette*

350

200, 255

*The change-over date to the #330813 water pump is still being researched, although Flint engine plant build records show the #3991399 pump in production 11/3/71. The latest verified casting date for #3991399 is March 1972. The earliest verified casting date for #330813 is April 1972. This indicates that April could have been the change-over date between the two pumps.

 

Pump #330813

Year

Application

Engine

Horsepower

1972

Corvette*

350

255

1973

Corvette

350

190, 250

1974

Corvette

350

195, 250

1975

Corvette

350

165, 205

1976

Corvette

350

180, 210

1977

Corvette

350

180, 210

1978

Corvette

350

175, 185, 220

1979

Corvette

350

195, 225

1980

Corvette

305

1805

 

 

350

190, 230

1981

Corvette

350

190

1982

Corvette

350

200

*See note at water pump #3991399

 

3. Big Block Water Pumps

Big block Chevrolet engines used the “short leg” water pump on all Passenger cars from 1965 through 1968, and on the Corvette. Pumps used after these dates were the “long leg” design. Note that although the terminology used is the same as for small block water pumps, the actual water pumps do not interchange. All big block water pumps had a bypass provision on top of the pump.

 

Front view of the big block #3856284 waterpump. Front view of the big block #3856284 waterpump.
Front view of the big block #3856284 waterpump.
This photo shows the location of the casting date and number of the big block #3856284 waterpump. The " H185" date code represents an August 18, 1965 casting date. Most Corvette water pumps use these types of casting dates.

 

Pump #3856284

Year

Application

Engine

Horsepower

1965

Corvette

396

425

1966

Corvette

427

390, 400, 425, 450

1967

Corvette

427

390, 400, 430, 435

1968

Corvette

427

390, 400, 430, 435

1969

Corvette (early)

427

390, 400, 430, 435

 

Pump #3940960

Year

Application

Engine

Horsepower

1969

Corvette*

427

390, 400, 430, 435 Short leg

1970

Corvette

454

390

*Early production cars could have had the #3856284 or #3940960 water pump. This pump was installed in some 1970 models

 

Pump #3992077

Year

Application

Engine

Horsepower

1971

Corvette

454

365, 425 Short leg

1972

Corvette

454

270

 

Pump #386100

Year

Application

Engine

Horsepower

1973

Corvette*

454

245 Short leg

1974

Corvette

454

270

*Some early 1973 Corvettes have been verified using the #3992077 water pump

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