Cylinder head flow - What is crucial in a stocker?

[Stan Weiss]

Originally Posted by B Parker

So, let's take a small block chevy. How much HP do you think it takes to pick up a tenth? To make it easy let's say a 69, 350/255 hp combo. BP

Just a rough guess. Around 12.5 HP.


Let me revise that to around 9.4 HP.



Stan

[Frank Castros]

I'm not attempting to doubt Stan's calculation but if we average it through the spectrum of the most commonly used combinations it's going to be roughly 10.0.
So of course based on the original question on flow of the intake and efficiency of the reversion on the exhaust side and based on a 88% + cylinder seal I believe you better have your ducks in a row to compete with the big dogs. One of the keys is chassis efficiency for sure.
If you can't run with big dogs, don't stay on the porch, find out why, it's not always $$$, it's dedication.

[Glenn Briglio]

Originally Posted by Stan Weiss

Just a rough guess. Around 12.5 HP.


Let me revise that to around 9.4 HP.



Stan

How did you come up with that number ?

[Larry Hill]

You want to manage the air on the outside of the car as well. Case in point on the truck the bed was off to one side. We centered the bed behind the cab and it picked up a little in et and MPH. An easy way to cheat is to cheat the wind.

[Stan Weiss]

Originally Posted by Glenn Briglio

How did you come up with that number ?

I ran some 1/4 mile drag simulations. After I ran the first one I realized I had used to fast of a car and reran it. Both my numbers are still only guesses. It is possible Frank's number is correct. This number will vary based on the class with A/S being greater than U/S. What is the weight of the car and what does it run for both et and MPH?


Stan

[Stan Weiss]

Originally Posted by Larry Hill

You want to manage the air on the outside of the car as well. Case in point on the truck the bed was off to one side. We centered the bed behind the cab and it picked up a little in et and MPH. An easy way to cheat is to cheat the wind.

Yes anything you can do to reduce Frontal Area or Coefficient of Drag (CD) will show up in reduced et and increased MPH.

Stan

[Paul Precht]

I have Chrysler's old formulas and graphs and I made my own with the info that I had back in the early 90s when I had my first machine shop. I'll scan them if I can find them but I seem to remember at 3,300 lbs a 12.20 et is about 10 hp per tenth, a 9.80 at the same weight is almost 17 hp per tenth. I broke it down from 9.50 to 16.0 and different weights can be used, a heavier car at the same et will require more hp per tenth.

[SSDiv6]

In the 1980's when I was involved with IMSA and SCCA road racing with the Mazda Factory Team, we were applying an industrial spray-on wax to the car paint finish that was manufactured by either Dow or DuPont, called Microfill. The intent of the wax was to fill the microporosity of the paint, enhancing the airflow over the body surface of the car. As I was told at the time, Mazda had discovered some aero improvement in the wind tunnel by applying the wax. At the time, the cars were being painted with DuPont Imron Epoxy Paint.

Nowadays, there are many products that contain nanoparticles with a ceramic compound that may do the same.

[Mark Yacavone]

So, lacquer primer...not so good, huh? :-(

( I was going to comment on the subject of this thread, but I don't want to stink it up, so I'll start a new one..Meanwhile, I've got to go and buff out my car for next weekend;-) )

[Stan Weiss]

Remember aerodynamic drag HP loss is not linear. This graph shows what a change from 0.35 to 0.34 for CD does.

Stan