This little gem is invaluable when calculating gear ratio/tire diameter/speed at "X" rpms/etc.  I had one made by Autolite back in the day, but must have given it away at some point.  I had put Stewart-Warner gauges in my '70 Boss 302 years ago and had dispensed with the speedometer.  Centered on the dash was a tach, so I needed to calculate speeds at given rpms so I could avoid getting tickets.  Never did I ever get a ticket for speeding by mistake.  Take a look at this thing.  It's small, portable, requires no batteries, etc.  Come to think of it, I probably gave the calculator to the buyer when I sold the car.

https://www.markwilliams.com/cal.html

There are others out there, too.  This one is $3.00.  A great little tool.

Yep, My '72 Pro Street Pinto barn find is set up with a Ford 9 inch, 4 link, Detroit locker, 15 X 15 x 34 rear tires. Dropping in a 500 CuIn Caddy torque monster, TH-400
thinking about a 2:39 or shorter gear to lower the wheel stands. Any comments?

Thanks, Paul

Combo is over 700 lbs with add ons you'll be well over 800 lbs......added to the front end !

I was thinking similarly. That is a LOT of weight hanging out in the front. I'd think the tires would break loose before the front end lifted. I never heard of going to 2.39 gears just to prevent wheel standing.

 My experience with my Datsun 510 was that with 3.90 gears and 215-50-13" tires the RPM's came up so fast (I was shifting into 3rd gear before crossing an intersection) there was hardly a perception of torque.  It was very similar to starting off on a 10 speed bike in 1st gear going down hill. When I went to 3.36 gears the torque actually became noticeable because it was being effective. Basically what I'm saying is gear ratio is torque multiplication but you can actually lessen the effect of the torque (because RPM's spool up too fast) to lift the front end by going to something like a 5.13 or numerically higher ratio. Every situation is different so this is an example not hard facts.

Obviously there is a "sweet spot" based on a cars weight the tire/gearing and the engine torque characteristic s. That sweet spot is where one would most likely achieve wheelstanding. But, I doubt with 800 pounds up front the greater issue won't be tire spin at the rear then lifting at the front.

2.39 gears would make more sense if the goal was to get any kind of gas mileage out of the huge motor. But, even that said, my Studebaker (350 Chevy, 700R4, 3.07 rear gears, 225-60-16 tire) is at something near 1,600 RPM at 65 MPH. Gearing like 2.39 would probably drop the RPM's to about 1,200 RPM at 65 MPH, not much above an idle. If this is truly a Pro Street car 2.39 gears are counter intuitive to that purpose of a car designed to go a 1/4 mile as quick as possible.

The bottom line is that using gear ratios to prevent wheelstanding rather than proper chassis management is not a good approach.

wHOOOOOO WEEEEEEE. although I'm impressed with all the replys, Every body take a breath and I'll fill in a few facts.
My "new to me" Pinto is a full on, tube frame pro stocker, built in the mid 70's. It's a close clone of the one Glidden campaigned in '72 - '73 (his was ladder bar rear, mine is 4 bar, with an upgraded halo, funny car cage) Mustang II front with aeroquip hat's and calipers. Worked over upper and lower "A" arms and adj. coil over shocks.

My intent is to pro street this old war horse and drive it 'till one of us can't do it any more.


The Cad motor I have in hand is the one I built to drop in a 225" W/B rear engine dragster, (1987 Richard Earl top alcohol car, dumbed down for fast brackets. (My home track was NHRA and ran a wide open bracket operation) First season, ran 10.00 flat in fast footbrake. moved up to super pro, without a box or throttle stop, thumped the suspended chassis guy's, and door cars, eating their injected 502's hangin' around the 9.90,s deadly consistent. An average night's work was  10.101, 10.103, 10.102, 10.100, 10.102, get paid.

The 472/500 Cad engine was designed by the same guy that drew the 455 Olds motor. the 500 Cad was much lighter, about 40 lbs, than a SBC in stock trim, and could be built to double the displacement, easily

Most engine dyno's can't accurately measure the horsepower because of the massive torque at low RPM. This one showed over 500 lbft of torque @1400 RPM. The torque curve is straight from 1100 RPM to valve float at around 5100 RPM. It really pulls much like a diesel. After all, this engine was built to drag a 7000 Lb around, smartly,quietly and smoothly. Published HP numbers were barely over 250 and the insurance companies and smog junk kept them from ever reaching their potential on the street and they were gone from the option list by 1976.

A lot of 502 and 572 BBC guys like to brag about big torque, mine, mildly built, will double the numbers they brag about.

I use the TH-400 because it was designed to stand up to the torque, (like the TH425 transaxle)

By the third season, I built a TH350, to gain back almost 60 lbs and a ton of parasitic loss horsepower. I rather enjoy blowing past a door car, running 130 MPH in the lights, at 165, with the 2.39 gears.

The weakest link in the big Cad, is the valve train. Anything much over 4900 RPM's they start breaking things, although newer, tougher parts exist, they are a bit pricey and not really necessary for the track, or the street.

I think the Pinto and the Bad Cad are gonna be a good match, I only posted to point out what gear selection can add or detract from performance.

I joined this board to get help finding body parts and, maybe to make a few meets for burnout's and such. I didn't mean to steal the thunder from some very impressive unibody cars.

Right now I'm searching for a one piece 'glass front end, Pinto or Bobcat. Any leads?

Thanks for your time,
Paul

 







 

Hi,
I have no desire to wee in the wind, or split hairs. It does indeed take olds pistons, custom rods and a welded  offset ground crank, along with a .120 pass with a boring bar, to get 769 CuIn. but it has been done, many times, There has even been big stroker's built for LSR cars, successfully.

Just pulling the cast iron intake manifold puts the caddy within reach of the SBC weight.

I know you guys are trying to keep the Pinto alive, more power to ya. I fell in love with the Pinto/Vega size rigs when I discovered that light weight and gobs of torque makes for a fun ride. Bob Glidden proved the concept.

Again, not trying to stir the pot or pic nits. For a long time, I thought the big Caddy's were only useful in pick up tow rigs. (and they still are) In a HP to Weight ratio numbers crunching battle the cad's look a bit weak against the SBF/SBC kids. However, horsepower is a calculation, Torque does the work. Lift the wheel speed numbers, with short gears, and fun things start to happen. The whole is MUCH more than the sum of the parts.

When my RED embarrassed too many door cars in the bracket wars, the whiners protested me out of foot brake, as a "center steer" car, (They could put the driver in the center of a Malibu, to see the tree better, but I didn't have a left seat to sit in, so I wasn't allowed to play) I just went on to own local super pro and index classes. They tried to protest me out of super pro because I wasn't running a box and throttle stop...(My RED, trailer, tow rig  and spares is on Craig's list, looking for a new home.)

I can see I've pissed in my corn flakes on this board, SO, I'll pick up my tool box and move along. The parts I need for my street toy are out there...

I wish all you guys the best of luck in your endeavors, C-ya

Paul