Good dyno testing requires making as many pulls as possible while theatmospheric condition
NTI instructors Luke Woroniecki and Rick Touchette led our dynosessions. After a 30-minute break-in session to allow the hydraulicflat-tappet lifters to mate to the cam, we made a few runs to establishour baseline setup. Timing was set at 38 degrees, the Holley carb wasoutfitted with No. 70 jets, and a 1-inch open spacer was used betweenthe carb and intake. Once we settled on these parameters, they were notchanged for the duration of the test. We also determined that holdingthe water temperature around 180 degrees F and the oil temperaturearound 195 degrees F would keep the pulls as consistent as possible.This provided us with 267.8 peak horsepower at 4,300 rpm and 349.7 lb-ftof torque at 3,600 rpm with the stock pan and 5 quarts of oil. Valvecontrol faded well before 5,000 rpm, so all pulls were run between 2,500and 4,500 rpm. The dyno cell used Nextel Cup-legal race gas. It wasn'tthe best choice for our heads, which don't feature a super-efficientcombustion chamber (like full-race heads) and only allow 8.5:1compression, but we saw little reason to change it. There is certainlymore power to be found in this Chevy engine by tweaking the tuning, butthis is the combination we felt would provide us the most repeatability.
Notice the kickout on the right side of this Champ pan (left in thisphoto) that extends al
One of the difficulties with this test is that the stock heads andlightweight springs we used significantly limited the rpm. Windagebecomes a much more pronounced problem the faster you spin the engine,and we were looking at horsepower changes that were quite small (as youcan see from the accompanying charts). Still, in racing, an extrahorsepower or two can make all the difference in the world, andimprovements of single horsepower that you see in the charts at 3,000rpm likely will translate to three or four at 7,000 in a full-blown racemotor. This is by no means an exhaustive test that answers everyquestion when it comes to oil control, but it does reveal a lot aboutwhat is going on inside an engine.
This chart shows how oil levels can affect power. Using the stock pandesigned to hold 4 qu
This chart compares the stock pan to Champ's dual kickout pan with awindage tray. Notice h
Varying oil levels in the racing pans didn't provide as much change asit did with the stoc
The Dyno Mule
Our baseline comparison of all three pans. The Champ pans had theirwindage trays installed
Our Chevrolet test engine was assembled with repeatability in mind. Wewere looking for changes in the range of 1-2 hp, and the dyno mule hadto be able to make pull after pull consistently. For that reason, wewere careful with the components we chose that would represent thepieces a racer may use but that would also work well through the stressof repeated dyno pulls.
Chevrolet supplied a stock long-block 350 with cast-iron 23-degree heads(non-Vortec), 8.5:1 compression, flat-tappet hydraulic lifters, andfour-bolt main caps for stability. The valves were 1.94 intake and 1.50exhaust. Properly tuned for power, the engine is rated at 290 hp with326 lb-ft of torque.
This chart was our big surprise over the two days we spent testing. Weran Champ's high-end
Since we were using a low-rpm engine package, a good dual-plane intakemanifold was a must to properly match the powerband. Weiand's new ActionPlus intake fit the bill perfectly.
The vast majority of all stock car racers out there use Holley-basedproducts, so that's what we wanted. We went with a 650-cfm four-barreland only had to make one jet adjustment to the jets.
A dyno mule needs to be as simple as possible. They aren't going to beused, so there is no need for brackets for an alternator orpower-steering pump. CV Products produces a pulley set for racers thatuses a square-tooth belt that is very adaptable. We ran just the crankand water pump pulley, and the toothed belt meant we didn't need anadjuster. This is perfect for racers who don't want to run an alternatorduring short events.
A Mallory HEI is the ultimate in simplicity and ease of use. The HEIdesign is upgraded with a hot coil that provides plenty of power wellbeyond 8,000 rpm.
NTI had never run anything on its dyno except Nextel Cup engines, sohooking up our wet-sump motor provided a few challenges. Another problemwe encountered at the last minute was that the stock valve coverswouldn't allow installation of a racing-style breather or relievecrankcase pressure. Bradley Auto Parts is a speed shop specializing inassisting stock car racers that we turned to for everything from aproper set of valve covers, to a multitude of brackets, plugs, andadapters, to a reusable oil-pan gasket to facilitate our multiple panchanges. Because the company specializes in racing, everything was instock when we arrived to look for a new set of plug wires at the lastminute.