I have to go with karlsd on this one I dont think you can over come the drag. By the way there is a big difference between 80-85 mph and 140.

 

>I have to go with karlsd on this one I dont think you can
>over come the drag. By the way there is a big difference
>between 80-85 mph and 140.

Yup. The force or air resistance increases with the square of speed. Thus, it takes four times as much power to go twice as fast.

Someone else pointed out that his 302-equipped truck is rated at only 210 hp and yet will do 80-85 mph. Let's use it as an example. It takes 2.83 times as much power to overcome drag at 140 mph as it does at 85 mph. If a truck with 210 hp tops out (drag limited) at 85 mph, it would need at least 594 hp to go 143 (not far off from my earlier estimate of 600). If the 210 hp 302 truck tops out at 80 mph, it would require 671 hp to go 143.

I think it is safe to say that it would take AT LEAST 600 hp to get a full size 60s or 70s vintage pickup to 140 mph. To do it, you'd need an extremely well built motor that is turning at very high RPMs for a FE. I think you could do it with a professionally built 427, but an amateur-built 390 is likely to fall far short.

In any case, it would still be ridiculously unsafe. The aerodynamic lift on a pickup at 140 mph would be so great as to almost permit takeoff. That means no directional stability or braking. On top of that, the driveline, bearing, brakes, tires, etc. simply aren't designed to take that kind of speed and would be prone to failure.

 

So Karl, If I read you correctly, this post was started on the wrong board, huh?
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John

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In the cool still quiet of night, you can hear chevies rusting away.

 

I say "go for it," just make sure make all your front end components and driveline are in good condition. Plus get some good tires and make sure your final drive ratio will allow you to get to 140 before you rev out. Heck, you'd probably be proud, I've taken my worn out 70 F250 Camper Special w/ 160000 miles on the original 360 2v and buried the speedo at over 100mph (although it may not be very accurate)for about 3 minutes going down a slight grade w/ my buddy w/ me and we thought that was awesome that old truck could do that. Plus it really did not feel that loose on the road either, just a lot of wind noise w/ the camper special mirrors and the windows down. Good luck

 

speed doesnt kill you...deceleration caused by the impact of another car, or a tree, or a bridge can, but speed itself wont.

140mph is not that fast, we are certainly not approaching the speed seen at the salt flats or anything like that.

Is it important that you approach this with the knowledge that your life (and possible the lives of innocent people) will truly be in your hands. If you end up killing yourself, well thats your problem. But do you want to lose control into a minivan full of kindergartners?
I hope you will attempt this in a "controlled" enviroment.
Any idea how long it will take drum brakes to slow that piece of metal down?

I say go for it, but listen to the advice of the earlier posts, and update your suspension, and drive train as well. write a little note to your parents, explaining why it is they went through all the fuss of raising you right, and how you could do this to them...et al..that way they will always have fond memories of you (in case you cut corners on safety, and end up killing your fool self)

Good luck

Drew

 

Hello its that guy with the 210 hp f100 Yes i can 80-85 mph in my truck with a 302, with the tailgait on and a THREE on the tree. If you were to cover the box or remove the tailgait you can decrease drag by 10% that is significant. so try your calculations again please. add in another gear, and your going to hit 100mph pretty easy. then double the horepower and 140 is within sight. I definately agree that safety measures need to be taken.


Scott

P.s. new wheel bearings help significantly, mine are 32 years old.

 

Adding another gear makes no difference, friend. Swapping a 3 speed for a 4 speed won't give you greater top speed, though it should allow you to accelerate quicker by keeping the engine in the power band more. In both 3 speed and 4 speed transmissions, the top gear is 1:1.

Top speed of any vehicle is determined by either redline/gearing or by drag. In some cars, increasing the final drive ratio (by adding numerically lower rear gears, an overdrive gear or something similar) will increase the top speed. In many others, however, increasing the final drive ratio actually LOWERS top speed, because top speed was already drag limited and increasing the final drive ratio resulted in the engine dropping lower in the power band. A good example is the manual tranny-equipped Corvette. A couple of years ago, I saw an article on a magazine test of a new 'vette. The data included determination of the top speed in each gear. The 'vette actually reached its top speed in 5th gear, and was SLOWER in 6th.

Also, dropping the tailgate and adding a topper doesn't significantly affect drag. That's a common myth. Drag is a function of the vehicle's frontal area, which is not impacted by those things, and the coefficient of drag (cd). While cd may be slightly impacted by lowering the tailgate or adding a topper, the effect is so small as to be negligible. Whether your truck is dusty or freshly waxed actually has a bigger impact.

Don't believe me? Ask any professional racer. They are very familiar with both the calculations and the power requirements to run at various speeds. If someone thinks they can get a 30 year old fullsize pickup to 140 mph without a host of major and expensive mods and add-ons, be my guest. I'll gladly eat my words if you can show me proof of 140 mph with less than 600 horsepower.

 

That simple drag formula you guys are tossing around has a lot of stuff rapped up in the Cd term. For instance a vortex forms at the back of the truck which causes lots of drag beleave it or not. I think with some brains you can get that thing to do 140mph. Be smart and take off the wipers, mirrors, trim pieces, hubcaps, etc. ; don't need a hubcap fling off at 140 and cutting someones head off. Lower the thing way down almost on the stops, you may have do some under side work to get the thing low enough to be stable at that speed. I've hit 110mph in my stock 68 390 4V F250 Camper Special sitting a little high with 33" tires, 4.33's, and a C6. Be smart with the gearing and you can hit it. If your going to do 140mph then convert the thing to rack and pinion the stock gear box is what will kill you tring to stay straight at that speed. If mine could go faster I would but the front starts dancing around because of the steering. Weight only slightly limits top speed! The weight will make you get there slower and only comes into play by increasing your friction drag in parts like the tires, so that extra 1,000 lbs will only bring your top speed down by about 5 mph, while increasing your time to get there by like 30-45 seconds.

 

I've gotta agree that you don't need nearly 600 HP. Take the stock 360 2V example above, doing over 100 mph...and that engine is barely rated at 200 HP (gross). If you can generate ~400 hp, peaking in the higher rpm range, have very high rear-end gearing, and of course all perfectly working suspension/steering, you should be able to do it.

Heck, I had a '74 Chevy Chevelle (not exactly an aerodynamic dream) back in HS with a +/- 350 hp 350 CID that would do 140 mph plus without a problem. How do I know I was going that fast when the speedo ran out way before? Simple, stop watch timing between mile markers on the highway...more than one to assure accuracy. I'm just happy to still be alive after thinking about some of the crazy stuff we did.

 

Force definitely goes with the square of the speed, but horsepower required goes up with the cube of speed.

You could do some coast down experiments and combine that with your weight and really estimate what it would take. There is a whole procedure for estimating drag and friction in the SAE Handbook.

I'm guessing that you may need to lower it, make a strong smooth steel cover for the box, and even design a pan to smooth the bottom aerodynamics. I forget what that pan is called, but finding an article on salt-flats-type racer's tricks would probably help.

And for your own sake, please don't forget the roll cage, fire suit, taking the fuel tank out of the cab and replacing it with a fuel cell, and all of that safety stuff.

Good luck, and please keep us posted.

--Matt



1972 F250 Custom Sport Camper Special 4x2 360 2v C6 3.73
Soon to have a 104" wheelbase as part of a Broncification project
My FTE Website -- http://www.clubfte.com/users/mlf72f250/index.html
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A Chevelle has significantly less frontal area and was in essence designed for straight line driving at high speed. An f250 Camper Special was not. Even if enough power can be obtained to overcome the drag. You still have to worry about lift. I would love to see proof of this task being accomplished but without some serious financial commitment I don't know that its possible. Add a drive shaft loop to your list of safety devices. A system with a center support bearing may not like being spun up to those kind of speeds.

Donovan 67 F100
ROchester NY

 

Hey do me a favor, before you attempt your 140mph... get your family to have a camera ready and take a picture of the disintegrated truck(and your) remains so they can post it on this forum after your dead...The issue is with the suspension not the high horse power engine...Old Fords were not designed to go that fast...The suspension mods alone could cost you over a grand, along with the $800- $1000 for new wheels and tires you'll need to do this with any safety at all...

What are you runnin moonshine in the Ozarks Billy Bob?

 

>That simple drag formula you guys are tossing around has a
>lot of stuff rapped up in the Cd term. [SNIP]

Actually, it's not a simple drag formula that I'm using. It is a very complicated equation that has nothing to do with drag racing. Drag formulas are useful for estimating ET and trap speed depending on the weight of the vehicle, power and gearing. I used a formula that calculates the amount of power required to overcome wind resistance at a particular speed. It is extremely accurate, and has been shown to predict top speeds of cars very precisely. The variables are basically the frontal area of the vehicle and the Cd. Admittedly, I had to estimate those, but I don't think anyone is arguing that I overestimated them. Actual Cd for a 70s vintage full size truck is probably significantly higher than the .50 figure I used for the calculation.

You can't do much about the frontal area, but you can reduce the Cd by modifying the truck. Doing all the things you talk about would certainly bring it down quite a bit, but it also adds considerably to the expense. My point is just that you're not going to get an otherwise stock truck to 140+ mph without making those major mods.

 

an old ford isn't going to fly, just like penguins,it
just won't happen.as for drive shaft, slip yolk etc, camper
special stuff is heavy. Hard suspension I mean hard. and
a huge motor like a 460 out of a 60's car, 500's and
472's are some good ones for moving heavy stuff very fast.



Fe power

 

It may not fly very far, but how much wind pushing up would it take to cost you control? The faster you go the more force the wind exerts on you. Jumbo jets are heavy but they get those in the air.

I don't know if the guy who's idea this is, is still listening...but if you are. It's your truck, your money, your time. Do what you want. I HIGHLY recommend against it. But if you're dead set and determined, I suggest that you take the time and do it right. You're going to need HIGH horsepower, lowered suspension, maybe a chopped top to cut down on air resistance, a covered bed, SUPER brakes, suspension in PERFECT condition, a sway bar for added control, high geared rear end, overdrive unit, and proper weight distribution. Also highly recommmended is all the safety equipment. Roll cage, racing harness to strap you in, fire extinguisher, relocated fuel cell, and all the other stuff I'm forgetting.

And one last and finaly plead. If you are going to do this, then PLEASE don't do it on the road with innocent people. Race track or something fine. But don't risk the lives of others for your own wild goals. This is SERIOUSLY dangerous.

-j.banks-