250 with aluminum head - weight, HP and ET calculation

[62Ranchero200]

Weighed the Ranchero on a certified truck scale today and with no driver and very little fuel it weighed 2,680 pounds, with 1,500 of that on the front axle and 1,180 of that on the rear axle. With a full tank of gas and including my weight, I calculate that the Ranchero would weigh 2,920.

If I estimate my flywheel HP at 180 to 200, and if I lose 25% of my flywheel HP through the C4, that should still give me 135 to 150 HP at the rear wheels.

Now I need to find an ET estimator and run the numbers. Of course, I know there are countless variables that determine actual ET - tire size and compound, rear axle type and ratio, the driver's reaction time and shift time, to name a few - but a good estimator would let me know what the Ranchero may be capable of.

Thanks
Bob the Builder

 

[xrwagon]

even better would be to go to a track, have a few runs, then work back with your weight.

 

[xctasy]

Weighed the Ranchero on a certified truck scale today and with no driver and very little fuel it weighed 2,680 pounds, with 1,500 of that on the front axle and 1,180 of that on the rear axle. With a full tank of gas and including my weight, I calculate that the Ranchero would weigh 2,920.

If I estimate my flywheel HP at 180 to 200, and if I lose 25% of my flywheel HP through the C4, that should still give me 135 to 150 HP at the rear wheels.

Now I need to find an ET estimator and run the numbers. Of course, I know there are countless variables that determine actual ET - tire size and compound, rear axle type and ratio, the driver's reaction time and shift time, to name a few - but a good estimator would let me know what the Ranchero may be capable of.

Thanks
Bob the Builder

The C4/7.875" diff combo will always take at least 39% off the flywheel hp with the best torque converter, and the 3 speed manual /7.875" combo removes 26.5%.


Then use:-

Ask Mr Werbly, the Gonkulator meister, he'll help.

The next best is http://www.wallaceracing.com/et-hp-mph.php

You put in rear wheel hp, which at 190 flywheel, would be 136.7

our ET / MPH computed from your vehicle weight of 2920 pounds and HP of 136.7 is 16.16 seconds and MPH of 83.62 MPH.

I've run the numbers else-ware

viewtopic.php?f=5&t=6711&p=46683#p46683

 

[WerbyFord]

Hi this is Werby-Not-Werbly (it comes from PowerbyFord on the valve cover but with the "Po" covered up, true story)

Be glad to guess at it, need:
* Compression ratio
* Quench distance (deck clearance & head gasket thickness) if you have em
* Cam specs:
* Duration at .050 (Im guessing 224-224 ???)
* Lobe centers (eg 108 is Lobe Sep and maybe 104 is Intake Centerline?)
* Header diameters (primary and collector)
* Primary pipe lengtghs & collector lengths if you have em (I measure each pipe out of the car)
* Exhaust pipes & muffs
* Belt drives eg just a fan (what kind)
* Air eg underhood air to carb or cold air tube or scoop

Some are details, sometimes I just guess at em but they all stack up

Of course it helps if afterward as xrw suggested, have a fun day at the strip, then we can compare real times & speeds.
To me that is the fun of it, not just "how fast it runs" but meeting your goals with a small motor

 

[xrwagon]

You really only need 3 timed runs, its a lot of fun, street cars is only basic safety equipment, i have done 6 meetings in my old girl, 46 year old motor, diff and gear box, almost 40 pass’s, no issues, except for a dud battery and a spat oil sender unit, my fun includes slowly creeping up on going faster with each modification going a little faster, hence my 13.403 to my flat 12.005 with only a dizzy swap, dropping the pipe and air cleaner and changing rear wheels for smaller diameter, being consistent is the key. I have run 12.606 on a 12.600 dial in at one stage, and have cut 0.014 light. Have fun and stay safe, remember these times are over the eighth mile.

 

[xctasy]

1/8 th mile is a very good way of assessing hp, since it eliminates some drag factor and cubic inch displacement to weight swings that most formulae forget to include. And the terminal speed won't be the straw that gets you time in a state prison if you've got a wrap sheet. The only guy to master the quarter mile to hp and et equations was David Vizard, with a formulae for varying kinds of wheel drive, drag, frontal area, gearbox and power to weight. Everyone else, with the exception of Powerby Ford, is just playing and rehashing around existing stuff.

The automatic trans is 9 times out of ten a greater than 39% sap on peak power, every chassis dyno test you do will most likely show a 50% loss on power from SAE net flywheel to rear wheel hp.


See the early Ford "Where Does All the Grunt Go" on https://fordsix.com/forum/viewtopic.php ... 90&start=0

Its in kilowatts, where each 250 Cortina and Falcon has 92 KW, but rear wheel kw figures of just 57.0 and 62.6 kw, or a 61/4 to 47.0 drop in % power on a very efficient BW 35 auto. The C4 power loss is even higher.

Automatics take care of launches by softening the flywheel effect that can so savagely create axle tramp on bigger 250 engined manual trans cars.