We began our testing with...
We began our testing with this setup-the Jesel MoHawk shaft rockers we ran for the past couple of years. NMRA has outlawed their use in Real Street. We wanted a baseline on what we ran in the past. You can see the titanium retainers and 31/48-inch pushrods that are also no longer legal. I'm going to miss these parts.
We looked at several things in our SpinTron test, one being our '04 combination. We wanted to see the kinds of forces we subjected our engine to that broke two valves. Next, we wanted to examine our '05 combination to discover what was responsible for its huge improvement in wear and tear. Finally, we looked at the new '06 combination. For 2006, the NMRA mandated sweeping changes in the valvetrain rules in Real Street. Pushrod cars are now limited to 160-pound spring pressure on the seat, steel retainers, no shaft rockers, and no larger than 51/416-inch pushrods. Other changes to the class include smaller 151/48-inch headers, 50 extra pounds and no bigger than a 3.73 gear ratio. This is NMRA's intent to attract more street-oriented racers to the class.
Our first test was educational: We were losing control at about 7,800 rpm. While the bounce was there, I would learn later that it wasn't as bad as it could be. This combination used the Jesel Shaft Rocker, 320 pounds on the seat (down from where we had set them), Trend Products 31/48-inch, 0.135-wall pushrods, and Manley titanium retainers. I learned later this was a good point to reference all other tests. This test was at 8,000 rpm. While not optimum, it would live without beating up the valve seats (see '05 Setup Graph, p. 156).
Next we removed the Trend Pushrods and installed a set of 51/416-inch, 0.080-wall pushrods we had run in 2004. The valvetrain was out of control at 7,000 rpm. Look at the graph to see what we were doing at 8,000 rpm. This was concrete evidence as to why I broke those valves. The pitch the engine made when it lost control of the valve was scary. I can't believe the valves held up as long as they did (see '04 Setup Graph, p. 156).
Here's the engine ready to...
Here's the engine ready to go. We used the same Trick Flow heads, valve cover, and intake we run on the car. The intake is there to keep the oil from spraying everywhere. As time went on, we only used the bolts for the valve cover and set the intake in place instead of bolting it down. That way, changes are much quicker.
That ended our first day, and I was depressed by what I learned. Knowing what the new rules in Real Street took away, I couldn't see how I was going to make any rpm and keep my parts from breaking.
The next day, we removed all of last year's components. Don worked on setting the valvesprings at their properly installed heights. He isn't used to working with these lame street-motor-type parts. We didn't have enough height on some valves and would have to run without seat cups. All the time, Don was grumbling about the new rules, and we had several items to test. First we had two sets of valvesprings. One was the single-conical style, or beehive spring. These springs seem to be the latest rage, and they've gotten a lot of ink because of their design. They are the same type of spring used on the Chevrolet LS engine series, and the advantages are myriad. They use an "ovate" string wound in a conical design. The small-diameter retainer is almost as light as titanium. The other set we tested were the Anderson Ford Motorsport Hi-Rev Series dual springs, which are more traditional springs.
The guys at Trend whipped up a set of 6.700-inch-long, 51/418-inch-diameter, 0.105-wall pushrods to comply with the new rules. Remember when someone would tell you they have "lightweight" pushrods? If they do, smile and be proud that you have the heaviest ones you can find in your engine. They fill up with oil, so whatever weight you save on wall thickness will be filled with oil. Oil isn't nearly as rigid as chrome-moly. The NASCAR guys use huge 11/42- to 91/416-inch pushrods. They may be heavy, but they don't flex.
If you look closely, you can...
If you look closely, you can see we have about 320 pounds on the seat. It had dropped considerably from where we had set it in 2005. These heads were pulled from the engine we ran last year. Don West brought along his LSM valvespring checking tool to measure the seat pressure, and we're assuming this will be the method the NMRA uses to check the new valvespring rules.
During our tests, Bob Fox was hanging around answering all our questions. "Generally, you will lose power when you get control of the valvetrain," he said. At first I scratched my head but later understood what he meant.
We installed the guideplates and Trick Flow 1.7-ratio rocker arms. We used the 71/416-inch ARP rocker studs. Things weren't nearly as dire as I thought (just don't tell the NMRA's James Lawrence or those pesky nitrous racers). I had hoped to see a stable valvetrain at 6,500 rpm. Things started to get out of control at 7,000, but nowhere near where it had been in 2004 (see '06 Setup at 7,000 Graph, p. 156).
In addition to valvesprings, we tested some hollow-stem valves from Ferrea. We know other Real Street racers use them successfully, but we saw only minimal gains on the dyno. Because of issues with keepers, we could not test the hollow stems with the conical springs. Back-to-back tests on the standard-stem valves showed the Anderson springs to be as good or slightly better than the standard stems. The hollow stems with the AFM springs were only slightly lower on the rpm range before they lost control.