Water Pump Recommendations?

[Scott Myers]

I have a 1970 SBC. does anyone have reccomendations for a water pump?
Summit racing (whom I like to order from) has about 7 different brands.
Is there one that works better than another, what should I watch out for?

[Joe L.]

Re: Water Pump Recommendations?

Scott-----

Your 1970 small block originally used the 55-70 short leg style water pump with 5/8" shaft and NO boss on the top for external bypass. It was of GM casting #3782608. If you want to maintain originality, your only option will be to obtain a rebuilt water pump with this casting. No aftermarket waterpump castings are available which are even remotely similar to this casting; all aftermarket have the large boss on the top for the external bypass which is unused on your application. GM SERVICE replacement pumps for your application have it, too.

If originality is not of too much concern to you, then I'd recommend a Weiand or Edelbrock aluminum water pump. These will have the boss on the top, though. Make sure that you get one with the 5/8" pilot shaft AND the 55-70 hub spacing. The pumps will have the dual hub bolt pattern, so this will not be a concern. These pumps have the large bearing and shaft assemblies as were used on 71-82 Corvette small blocks and all big blocks, but you MUST have one with the pilot shaft turned down to 5/8", as I mentioned. The large bearing and shaft assembly is a BIG advantage with respect to durability of the pump. It is not possible to install one of these bearings in a "608" casting, so if you "go original" then you have to be staisfied with the original small bearing and shaft.

[Scott Myers]

Re: Water Pump Recommendations?

Thanks Joe, I see that the Weiand pump recommends an extension kit
for my year with the long style but not the short???
Since I am not to concerned with originality any aftermarket one will
do. I like the brands you have recommended.

Thanks again

[Joe L.]

Re: Water Pump Recommendations?

Scott-----

You don't need the extensions. These are to convert a short leg water pump to a long leg water pump. No Corvette ever used a long-leg water pump (except 92-96 LT1 and LT4 which use a COMPLETELY different design water pump for reverse flow cooling).

[Duke W.]

Re: Water Pump Recommendations?

If you have a sound casting and it fits find a local water pump rebuilder and have the existing pump rebuilt with a "ball-roller" bearing.

Duke

[Scott Marzahl]

Re: Water Pump Recommendations?

Has anyone ever seen the Stewart water pumps. I see them advertised as NASCAR type hi flow water pumps. Do the Weiand and Edelbrock pumps have cast or stamped impellers?

[John H.]

Re: Water Pump Recommendations?

Scott -

What differentiates the Stewart "NASCAR-type" pumps from the rest is the impeller, which is designed to run at 8000-9000 rpm continuous without cavitating; hardly necessary for a street-driven car. A stock pump will work just fine if the rest of the cooling system components are up to snuff; in 40 years of engine work, I've never seen a cooling problem that was caused by a water pump (although Summit and Jeg's would have you believe that the "NASCAR" pumps will solve all your cooling system problems).

[Duke W.]

Re: Water Pump Recommendations?

Interesting comment, John. If the impeller is designed not to cavitate at 9000 RPM then its flow rate would be lower than OEM in the normal rev range of a street engine.

A 1992 SAE paper on the LT1 engine indicated that water pump flow rate was dictated by cockpit cold weather heating requirement, implying that flow is higher than necessary for engine cooling.

Given this, how does one reconcile the "high flow" characterization of some aftermarket pumps.

Another reason why OEM is best.

As a point of reference the standard Vega 140 water pump delivers about 15 gals/minute at 2000 RPM For the Cosworth Vega the impeller was redesigned to drop the rate to about 12 gallons per minute at the same speed, both in recognition of the engine's smaller displacement and it's higher rev range.

The impeller design for a NASCAR engine would be unsuitable for a street engine and vice versa.

One my '63 SHP engine, the water pump is slowed down relative to the 250/300 HP engines via the pulley ratios.

Duke

Duke

[Joe L.]

Re: Water Pump Recommendations?

Scott-----

Yes, a higher flow rate pump is not necessarily better as many suppliers would have folks believe. The OEM water pumps have a flow rate designed into them which is optimal for STREET operation, which is the most important regime for most folks. There is such a thing as TOO GREAT a coolant flow rate. In that case, coolant may be pumped through the engine at a rate faster than the radiator can efficiently dissipate it. In that case, overall cooling system efficiency and performance is DECREASED rather than increased by a "high flow" water pump.

As is usually the case, OEM components are optimized for street operation. Some folks, especially "immature folks", assume that components designed for racing must be better for their primarily street car. They reason that the OEM manufacturer of the car would have done it that way were it not for their attempt to "save money". The majority of the time, they are dead wrong; things were actually designed the way they were for a VERY GOOD reason. The "uninitiated" often find out the hard way the consequences of such modifications and "improvements" on OEM design.

Notwithstanding the above, it is sometimes possible to improve on OEM design and functionality. However, it needs to be done VERY carefully and with consideration of ALL the factors, not just the seemingly obvious ones. In my opinion, for most "purely street driven" cars, attempts at "improving" the OEM design will result in an OVERALL DECREASE in satisfaction with the car. You just can't "field re-engineer" a vehicle and expect to "improve upon" the basic engineering, costing multi-millions of dollars, that went into a car. To me, that notion makes absolutely no sense, at all.

Of course, none of the above applies to vehicles modifed for racing applications. Racing applications have a whole different set of vehicle priorities, few, if any, of which were designed into the car by the OEM manufacturer. To CONVERT a car for racing purposes does require MANY modifications from the original configuration.