My '95 gt (5.0L) governs out at 120, in 5th. I'm not sure about those ohc 4.6L. but I know my vehicle sticks so well you don't really notice you're going that fast till you look over and everything is passing bye... I don't know about classics. mine hasn't hadanenginein almost 20 years

 

i took my stock 67 with stock suspension up to 125-130 racing an 03 gt on the interstate, i didnt stand a chance, but hey i was wondering anyhow, and decided maybe this isnt a good idea....i dont like tickets.

 

You clearly stated 4800 RPM in 4th gear. 4th gear is either a straight through gear or underdriven (for aftermarket trannies). For that to be possible with the quoted 3.73 gears, you'd need 37" tall tires. Stockish 2.73 gears will get you close with stock tires, but are still a shade under 135mph with stock height tires.

The diameter of your wheel means nothing. The 16" wheels on my Explorer turn fewer RPM on the highway then the 17" wheels on my '03.

BTW, what kind of classic do you have that shows a speed of 140MPH?

 

My car never goes over 120mph....according to my speedo anyway

 

I drove my mustang at a typical 100 to 110 on the high way for about 250 miles. Didn't sway, take off and fly or anything. I mean 110 is different than 120 and up but the only thing I noticed is a vibration throughout the car because the tires suck and the engine shakes the car. Other than that it seemed relivively safe. But as soon as I hit some wind to the side of my car it just about put me into the lane to the left or right of me. Thats just my expirence.

 

I used to do 100-110 quite often in my classic stang back when I was younger (and dumber). These days 80 is plenty fast for me in that car.

My fox body stang was only good to about 120, and it'd do it all day long. At 125 and it'd start to feel like it was going to come off the ground. I've only had my 2005 stang to about 120 and it was totally happy there. It's so heavy, that Ibet it'd be good to about 150. But when it comes to the classic, I think 70-80mph is a good top speed for anyone that doesn't want to find themselves all of a sudden in the wrong lane...or ditch.

 

All I know is my car is extremely stable at 110 mph going through the traps, and my car isn't designed for 1/4 usage.

 

Your '68 isn't nearly as aerodynamic as a C5/C6, a 4th Gen F-body,or most anything else built in this century that has that sort of power.

I doubt that 450 WHEEL hp will get you past 165 - 170 with 1960's aerodynamics and whatever ideal gearing would be required to put your rpm's at peak power when you're up there.Make that no more than 155 - 160 mphif that 450 number is crank hp. 190 mph is going to require something more on the order of 600 - 640-ish wheel hp (~750 crank?). That's assuming that aero lifting of the nose doesn't hurt your drag coefficient enough to make those estimated speeds and 190 mph hp numberspurefiction. Those are quick (but reasonable) answers. I have a (large) spreadsheet that can give a pretty good top speed estimate if you have enough of the required input data.

Note to those with 120-ish speeds - that requires MUCH less hp (barely over 200 at the crank). Top speed running is a funny thing, and you either need to have made a run up to where there was absolutely nothing more to be had, or have a sound enough grasp of the physics involved to have much idea what goes on up there. The point I'm trying to make here is that when you're at 120 (or 130 or 145 or whatever) and the car is still accelerating enough to feel, you just can't see how quickly the aero will put a stop to the continued fun or (quite) when it will happen. The last mph that you can possibly add can easily take more than half a mile to get. The next-to-last mph can be built upin only a few hundred feet. You won't feel either, or be able to watch the speedometer move for either - the acceleration really is THAT slow.


Norm

 

If you're wondering what Mustang has speedo that goes to 140, then the answer would be the '65 GT's and all of the '66's.

 

The 67 / 68 Shelby GT 500 cluster goes up to 140. I just had to have mine converted to the 140mph / 8k tach for no other reason than it is just so. damned. sexy!!