So I rode a 205HP VMax today...., Got me thinkin Options

[DBCooper]

I'm very aware of the weight difference between a car and a bike. My 914 came with a 67 hp, 99 lb/ft bus motor and I had a blast driving it. So I guess my question is: Other than flywheel weight, does it matter where the motor comes from? If a motor makes a certain amount of torque and hp, does it matter if its a type 4 or from a Yamaha? I've seen lots of money thrown into a type 4 that has a lot less than 200hp and 130lb/ft torque.

I do understand that a 914 wouldn't be the best choice for a motorcycle engine swap. Most motorcycle engines make 0 power below 5k, but some of these motors are different. The rocket III starts making power at 1200 rpm or something like that..

Sure, but keep in mind that motorcycles are made to be lightweight, so that's what motorcycle engines are designed to push around. They reduce internal friction by running larger (almost race) clearances, the bearing shells are narrower and thinner, rings are thinner, very short skirted pistons for high RPM's, lighter rods, crank's lighter with smaller journals, etc, etc. So they do make large HP and torque for their size, but give up strength and longevity to do it. When I dump the clutch in my car I've been breaking CV joints, in a Hayabusa powered 914 I'm pretty sure I'd be breaking crankshafts. A nice LS1 will produce more HP than a 14 liter Cummins diesel, but if you put an LS1 into a semi truck you need to adjust your expectations, for obvious reasons. I'm not familiar with the Rocket engine except from photos, so it might be a truck, I don't really know.

Don't misunderstand, I'm all in favor of swaps and moto powered cars can be fun. Like I said, I have a Seven replica, have met some of the Hayabusa/Fireblade people in England and seen their cars. And original Morgans, of course. But all those cars are a lot lighter, and the work involved with that swap is nothing to sneeze at, so if you're going to do all that work hopefully the HP/weight gain will be worthwhile. Especially if used on the street. Bob does great projects, and that Fiat has a history in the VW world, so I look forward to see how his turns out.

It's always fun to stir the pot, my only advice is to study it carefully before you decide. And who knows, maybe if a bunch of moto engined 914's show up the Porsche purist/concours contingent will look on me with less skepticism. Nah... probably not.

[jhadler]

I'm very aware of the weight difference between a car and a bike. My 914 came with a 67 hp, 99 lb/ft bus motor and I had a blast driving it. So I guess my question is: Other than flywheel weight, does it matter where the motor comes from? If a motor makes a certain amount of torque and hp, does it matter if its a type 4 or from a Yamaha? I've seen lots of money thrown into a type 4 that has a lot less than 200hp and 130lb/ft torque.

It's a lot more than just raw torque and hp. First off, it's about torque and hp at given rpms. Look at the torque curve of a four banger car motor, and compare that with the torque curve of a motorcycle engine that is rated for even twice the same power. You'll see that there is NOTHING near the bottom end where you need it to accelerate a car away from a standstill. Second, and more importantly, it's about how much load the drive-line is under when accelerating. The internals of the motorcycle engine don't need to be that beefy to withstand the load of accelerating even a 600 lb chassis. The internals of a car engine need to be a lot stronger to withstand the load of accelerating a 2000 lb chassis. This is why MC engines can be so small and light. The crank, rods, etc do not need to be very stout when they're really not subjected to much load. Those same internals for a car need to be a lot stronger as they are working against a much heavier load.

-Josh