Sunday

Back to the Throttle



Back to the Throttle
By Don Terrill (c)2005

"I can build more power than you can hook."
---Stock Car Engine Builder

"Nope, I can hook anything you can build."
---Car Owner, Driver & Crew Chief

I've had this exchange at least a dozen times. How often have I been successful at convincing them to build less? Never. How often were they right to build more? Never. Maybe it's just the short tracks here in Michigan, but building too much power for these tracks is easy.

How do I know? I ask the driver one question; "At what point on the track are you at full throttle?" When I hear; "The Flagstand" I know they have WAY TOO MUCH power.

Maybe it's just my drag racing roots, but to me it looks like the first one back to the throttle wins. In the end, I guess it's who has the most usable power, or maybe who knows how to use their power the best.

What is usable power? Not one single horsepower more than the track can handle at any given point on the track. Now, if the driver were a computer he could easily have perfect throttle position at all times. For a human this is impossible, and the more over-powered the engine becomes, the slower the driver will be.

Building usable power: To me it's all about building less power at low rpm and more up top.
  • Less cubic inches - Everything being the same, less cubes means less power, but more importantly, a power curve that moves up.
  • Bigger/Better heads - Better heads typically make the majority of their extra power up stairs. For example; The Chevy SB2 head will move the torque peak up 500-600 rpm when compared to 18 degree head - which is no slouch.
  • Bigger/Better intakes - Not as dramatic as cylinder heads, but still a move in the right direction. In fact, I think the intake is a great tuning aid for short track racing.
  • More camshaft - By more I mean more duration. This will soften the engine down low and help it breath up stairs. Perfect!
  • Less compression - Typically more compression means more power everywhere, but if the increased compression comes in the form of a big dome, it may help more at low rpm than high. Not what we want.
  • Bigger/Shorter headers - Can act the same as an intake manifold change. Another nice tuning aid.
A combination I'd like to see racers try: 300 cubic inches with SB2 heads and 9 to 1 compression.

What I see built too often: 377 (or more) cubes, 23 degree heads and 13.5 to 1 compression.

A good combo that is being used today: 355 cubic inches, 18 degree heads and 9 to 1 compression. Not bad, but if they would step up to the better heads they would see a dramatic shift in their torque curves - one for the better.

Of course, none of this advice is needed if you're running a sophisticated traction control system. In that case, the driver is a computer. That's for another article though.

Think I'm out to lunch? Fine, write your own article