Race Car Tech Help?

Question

I drive a Super Minicup RaceCar at Seekonk Speedway in MA. We recently had the engine rebuilt by a really good engine bulder who knows his stuff. We have had two weekends of racing and every single restart we fly out of the box into the lead and get about 4 car lengths in front of everybody and then suddenly it feels as if the car gets tighter (may be because the car gets slower, so it feels tighter) and everybody cathes up and blows by us. I have come to the conclusion it is the gear ratio or the valve springs in the Engine. I checked the Valve springs and they are set just right, right where the engine builder told us to put them. We are Stumped... It has nothing to do with the chassis set ups, we were fast all last year with the setup, and plus we fire out on the start and stay out front for 10 laps.. ANY HELP IS GREATLY APPRECIATED! THANKS IN ADVANCED!!

Answer 1

deffently check the gear ration       i would say your floating a valve spring

Answer 2

there are so many factors involved when you run into a problem like this.you need to take into consideration that your tires may be part of the problem by tightening up the car and scrubbing off speed in the corners.also you need to look at stagger(yes you can "grow"spec tires for stagger by filling them up to around 40 pounds and setting them in the sun for stagger) you are running in a spec engine class but with some liberties to the valve springs however i used to run honda engines in the 80s in sprint kart racing and i would keep track of the weather and adjust the valves tighter or looser to compensate for the added heat growth in the engine,the hotter the engine the looser i run the valves.honda makes a good engine but the valve springs are made for long duration governed running so racing with them without a govenor will float the valves but your engine builder knows this but make sure that there is no galling to the valve stems and followers and no growth clearance problems.other than that i used to run my engines as loose as the rules allow.

Answer 3

You may need a gear ratio change. A stronger engine needs a slightly higher gear. Call your engine builder and ask. How is the rpm compared to before?

Another thing to try is closing the plug gap. If the gap is too wide for the increased cylinder pressure of the new engine it will limit rpm. Cut the plug tip back to center the tip on the center electrode and set the gap closer than you have been.