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The First Generation Ford Mustang:
They felt slow, but that was deceptive.

Saying that a 3,500 pound first generation Ford Mustang from the late 1960's traveling at 140mph is analogous to Eva and her trailer going 70mph is referring just to equivalencies of kinetic energy (mv^2=mv^2). The reality is somewhat different for required breaking power. The Mustang going 140mph is actually going to slow much faster when the accelerator is released because air resistance up at that high speed is really quite huge. In fact it requires several times more power to push a first generation Ford Mustang up to 140mph than it does to push Eva up to 70mph. Anyone who has driven a first generation 289 powered Ford Mustang with an automatic transmission might scoff at my estimate that they can go 140mph, because in stock form they felt rather sluggish. The problem was that the very short 2.87" stroke of the 260 and 289 Fords did not get along well at all with a low stall speed torque converter. Upwards of 300 cubic inches was plenty for normal driving through the torque converter at 2500rpm, but getting any kind of real power required at least 4000rpm. With an appropriate camshaft and valve springs capable of holding the lifters in contact with it a stock 289 will scream at 6000RPM making well over 300hp. A totally built out 289 with ported heads and an intake and headers to go with them is perfectly capable of 500hp at 8,000RPM and above. And that might even be pulled off with stock pistons and rods because the stroke is reasonably short. The main problem is the same as for any of the push rod engines. The two valve per cylinder configuration requires a radically aggressive camshaft to get it to flow at higher engine speeds and that radical camshaft is going to require a whole lot of valve spring pressure to keep the valves, springs, retainers, rocker arms, pushrods and lifters moving in sync with the fast lifting camshaft lobes. If the performance build were attempted with the small 1.78 inch diameter intake valves found in most stock small block Ford heads instead of the larger 1.94 inch diameter intake valves that will easily fit in the four inch bore the problems with getting the engine to flow at higher engine speeds will be even more severe. The tiny little 1.78 inch intake valves and 1.45 inch diameter exhaust valves are a carryover from the original 1962 to 1963 221 cubic inch small block Ford which had the same 2.87 inch stroke crankshaft but just a 3.5 inch bore. In a stock first generation Ford Mustang the sluggish performance had nothing to do with valve train limitations, and instead was a simple matter of a low stall speed torque converter working unusually poorly with the short stroke engine. As a point of reference a 1990's BMW with a short stroke four valve per cylinder 2.5 liter inline six capable of insanely high power output at 6000-8000RPM still feels really slow with the automatic transmission because off the line the engine speed stays way down at less than 4000RPM for what seems like forever. At any engine speed torque converters take their toll, sucking off a quarter to a third of the power but this ends up being only a slight performance handicap in many situations as missed shifts take a large toll on performance as well. For most real racing though manual control of gear changes work better simply because the driver does not get surprised by a shift that breaks traction when setting up for a turn.

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