Boy does this sound familiar. I did the same thing. My boat-tailed car is
also street legal, so I ran it up the freeway, and when I got out of town I
tached it out and it pulled strong to over 125 with about the same gears you
are talking about (altitude around 2800 ft, dry and hot). I road race this
car and have had it clocked at 126 at Willow Springs Raceway in California.
I went to Bonneville and it pulled strong in low, and second then third
pulled up to around 2800 I think, for a time through the traps of 88 mph. A
flathead just won't breathe at Bonneville for some reason. I dropped gears
until I was at around a 3.48 (within a few percentage points of a stock ring
and pinion setup-what a drag!) and finally went 118 at a little over 4000.
Which is where the record stands. If you are doing 125 on a 255 flatmotor
in an open wheeled car you are doing well. I think you are fighting
aerodynamic drag more than anything else, including weight. You didn't
mention how heavy the car is though. Open wheels are like four pumps
pushing the air on their top surface forward at twice your speed. Also,
according to my spreadsheet these are the speeds at various RPMs for your
car. (I use measured tire circumference rather than just a diameter as I
believe it to be more accurate):
1000 29.21
1500 43.81
2000 58.42
2500 73.02
3000 87.63
3500 102.23
4000 116.83
4500 131.44
5000 146.04
5500 160.65
So if you were doing 125 at 4900 and 125 with zero slip would be at 4780,
then your slippage was around 2-3% which isn't too bad. Now, tell me
everyone, did I do my math homework correctly?? Sorry, not too many
solutions. In road racing you take away weight and add more lightness. For
Bonneville it's take away drag and Make more Horsepower!
Dave Seely
1141 XF/VOT
117.955 mph (OK so I rounded up, shoot me!)
----- Original Message -----
From: "Phillip Landry" <saltracer@hotmail.com>
To: <land-speed@autox.team.net>
Sent: Friday, August 23, 2002 7:39 PM
Subject: Weight matters?
> Ok, I believe our race car is too heavy. I come to this conclusion because
> the motor struggles to build rpm in third gear. Most people have contended
> that weight is not critical at Bonneville and actually helps traction and
> stability. We are running a kinda small (255ci) flathead and I'm thinking
if
> we lowered the weight of the car our overall performance would improve.
> Don't ask the weight of the car, we haven't weighed it yet. It's a
modified
> gas roadster with a frame made of mostly 2x2 square tubing.
> Also, how much slippage should we expect from our torque converter? We
> crossed the finish line at 4900 rpm with 27" tall tires and 2.75 gears and
> were only doing 125mph. Phil Landry
>
>
>
> _________________________________________________________________
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