Pumping Losses

TEST ENGINE PARTS

Short block parts from Powerhouse
Crank #661-861-0125
Pistons #H345NCP .040
Rings Speed Pro E251K
King Bearings, Mains MB 557AM, Rods 807AM
Pioneer Balancer & Flexplate
Federal Mogul gasket set #260-100
Approx price $500

Valvetrain
Isky Hyd Roller cam #201265/272
HR lifters #2020
Pushrods #203-96
Timing set #300TS

Edelbrock Equipment
Cylinder Heads--E-Tec 170 #60979
Intake Perf RPM Air Gap #7516
Carb AVS #1806
Valve Covers #4153
Water Pump #8811

Ignition
Performance Distributors HEI w/ Live WiresOil system--Moroso

Machine Work & Assembly
Speed-O-Motive

Pumping Losses
We began our testing using a Weiand PN 8240 mechanical water pump, which, although made from aluminum, still runs a stamped-steel impeller, just like the impellers found in stock pumps. We felt this would be most representative of street power. We ran the pump overdriven first, to show the most power-robbing setup. Then we switched pulleys to see how much power could be gained by underdriving it. Lastly, we tossed the belt in favor of an electric pump to find the most power possible. You'll also note that we started all tests at 3,000 rpm. That's because pumping losses below that speed were minimal.
Test 1--Weiand #8240 mechanical pump, March #06061-6152 OVERDRIVE pulleys (5 1/2" water pump, 7" crank) 127-percent overdriven

Test 2--Weiand #8240 mechanical pump, March #06051-6052 UNDERDRIVE pulleys (6 1/4" water pump, 5 1/2" crank) 14-percent underdriven

Test 3--Weiand # 8217 electric pump.

WOULD A RECING PUMP HAVE WORKED BETTER?

You're probably wondering why we didn't also test a Weiand Team G race pump? That's because, while those pumps will use even less power to run than the street pump, they're designed for a higher rpm usage than this motor would see. The racing pumps are typically made for circle track engines that rarely run below 4,000 rpm. Our street engine will rarely see above 4,000 rpm so we thought that'd kinda' be like running slicks on the street. Sure, we know it'd work better, but it doesn't make sense for the everyday commute. Also, race pumps have impellers that are designed for efficiency at high rpm and will flow even less water at idle. Therefore, they may also cause overheating in traffic, just like underdriving your pump might do.