Re: About to sign on the dotted line
Just a quick question, I have a zf 5 speed in my cav gt 40. Can it be strong enough for the 700 hp out of my 427 hammer motor or should I be looking elsewhere? tom
I only know one guy who routinely breaks his ZF. He has a 750+ hp motor in his dedicated race Pantera, and he just drives the hell out of it. The problem is that he is extremely abusive to the car. I think I've mentioned him before on this site; he is just like Animal, the drummer in the band on The Muppet Show. He just gets the red mist and starts pounding the hell out of the car, and eventually the gearbox goes. On several occasions, Lloyd Butfoy showed me destroyed pieces out of his gearbox, and he's just astounded. This guy has managed to find new and innovative way to break things previously thought unbreakable.
Each year, he races against Dennis Quella, who also has a ZF in his 700+ hp Pantera. Dennis is a sympathetic (although extremely aggressive) driver, and has NEVER had gearbox problems as far as I know. They are both evenly matched on the racetrack, which just shows that you don't need to be abusive to be fast.
Oh, wait, I know of one other person who blew up a ZF. He had a 572-inch stroker in his Pantera, and did side-step-off-the-clutch drag race launches and burnouts, again and again and again, showing it off to dozens and dozens of passengers. After a few months of nonstop abuse, it finally blew apart.
But these are obviously extreme cases. Somebody who drives normally (that is, somebody who takes no special precautions, but has enough mechanical sympathy to not over-rev his engine or lock up his brakes, or bang gears without using the clutch etc.) should be able to make a ZF live forever, even with 700 hp in front of it.
Speaking of which, I have to ask, is the 700 hp of your motor 'advertised' hp, or has your engine builder provided dyno sheets to prove it to you? And what sort of exhaust system was it measured with? Dyno exhaust systems are almost always heavily optimized relative to the exhaust that the motor actually gets to use in the car. My 427 Cobra's motor dropped a full 110 hp when it was run with the standard Cobra sidepipes and headers, versus the dyno exhaust system (I subsequently modified the Cobra exhaust and hopefully got a fair bit of that lost horsepower back, but have no illusions that my motor is making as much power in the car as it is on the dyno).
My point is simply that it's quite likely that even if, in a best-case scenario, your motor does actually generate 700 hp on the dyno, by the time it's installed in the car, choked with an air filter and plugged with an exhaust system, that the power level will be at least a bit lower.