I've always heard that a boosted motor needs to be durable. Why does a boosted motor need so much more durability than a NA motor?

I have always understood that a motor producing 500hp will have a certain combustion pressure regardless of the induction system. Based on my understanding the NA motor would have to be just as durable as the boosted motor. To take it further, it seems to me that the NA motor would have the highest potential for failure because the power would peak at a higher rpm so there is less time between combustion cycles for things to, for lack of a better word, relax.

So what is the deal with boost?


Lawrenceville, GA

Charlie,

        Different areas of strength. A normally aspirated motor won't see the cylinder pressures that a blown motor can generate. BUT it will usually need more RPM to achieve the hp numbers, So the bottom ends and reciprocating parts will take beating. Remember from you high school physics that the amount of force goes up with the square of the velocity. Rods, pistons, and the bottom of the block (main bearing webs) as well as the crank must be much stronger and lighter reciprocating pieces are a major benefit. Blown motors, where the mixture is forced into the cylinders don't have to spin as hard to see big HP numbers. But boy do they make torque, On ther dyno at ESI my F code made over 425 ft lbs at 3200 or so rpm. The torque curve starts to drop after 4000 /4500 because with stock valves I run out of cylinder head at that point. I've made changes to the motor since the dyno runs that have extended the range, but it's still a low rpm motor. But, the walls on my motor are fairly thick and stiff, because we wanted to be sure we didn't lose ring seal and pressurize the crankcase, no horsepower there.

     Ted or Wally or Dave on the other hand, don't make the torque numbers I do, But they all bury me on the Horsepower end from 4 grand up. Make sense? 

Frank/Rebop

Bristol, In ( by Elkhart)