How about a 8.2" deck small block Ford, aluminum block (Dart), 3.25" steel fully counter-weighted crank, SVO D3 high port cylinder heads (requires 4.09" minimum bore). 341 cubic inch displacement (4.09" bore x 3.25" stroke). Topped-off by a wild looking "custom" long runner (not IR) fuel injection system?
This engine is more compact than any 400+ horsepower engine Ford currently makes, or has ever made, by virtue of the short deck height and the relatively narrow OHV cylinder heads (narrower than DOHC cylinder heads). It can be considered a hybrid like the Boss 302 as it combines a small block Ford short block and canted valve racing cylinder heads. Overall the little hybrid I've suggested is my idea of what a sports car engine should be, compact, light, with the right "linear" power delivery and crank arm leverage for a light weight sports car and capable of making more than enough horsepower for street tires. It is very over-square compared to Ford's modern engines. This allows for larger valves. Piston speeds are in the ball park for a street operated sports car engine. The shorter crankshaft stroke reduces frictional power losses in comparison to Fords modular engines. The rod length to stroke ratio is good (~1.65:1) for a 7500 rpm motor. The rev limit will depend upon how you set-up the valve train. I'd recommend a hydraulic roller cam used in conjunction with solid roller tappets. The D3 heads were the latest small block Ford racing heads before the new FR9 racing motor was phased-in during 2010. The intake ports are about 1" higher than the intake ports of the iron 4V cylinder heads! You can have the heads ported to provide what ever power band you desire, use the biggest intake valve the ports will support, and have the combustion chambers configured to operate with whatever octane fuel you choose. How much technology the engine offers simply depends upon how you decide to equip it ($$$). There are all sorts of cool parts readily available and priced competitively for the small block Ford! A short water pump and serpentine belt drive would make a flat bulk head possible. Sparks can be provided by a crank triggered, coil near plug ignition (GM coils). Dry sump lubrication would be a great addition. Combining the shallow oil pan of the dry sump system with a small diameter flywheel, small diameter multi-plate clutch, and a flipped-over ZF would make it possible to install the engine lower in the chassis for significantly lower CG and improved handling. If mildly tuned an engine like this can provide good fuel economy when the owner keeps their foot out of it. And even in a mild state of tune it will have the potential to make more than 500 BHP, heck probably more than 600 BHP. Thus equipped the engine would have plenty of technology wrapped-up in it, lacking only variable cam timing and direct fuel injection, and perhaps the DOHC 32 valves some people equate with modern technology.
The customary reason OHC cylinder heads were preferred over OHV cylinder heads was the elimination of the push rods which accomplished two things: (1) it allowed the engine to rev to higher rpm, and (2) there was less obstruction in the width and placement of the intake port. A nice 3/8" OD push rod made of 0.080" wall thickness seamless chromoly tubing is stiff and light, and allows a typical street engine with typical valve spring force to rev to very high rpm. The Ford canted valve cylinder head splays the pushrods far enough apart to provide for ideal placement and width of the intake port. Four valve cylinder heads allow for increased "valve curtain" area, but canted valve cylinder heads also allow for very large intake valves, having generous valve curtain area as well. The shallow combustion chambers and centralized spark plug location of Ford's canted valve racing cylinder heads also provide good combustion behavior and high thermal efficiency. In terms of a 7500 rpm street engine a DOHC 4 valve cylinder head offers no advantage over a well sorted out Ford canted valve racing cylinder head. And its much easier to time 1 camshaft than it is to phase 4 camshafts!
Something like this is obviously not available as a crate engine, its not for everybody, but I hope it is food for thought or discussion. It would be at least as expensive to build as the $9300 M-6007-Z427FFT crate engine mentioned by Chris, if not more so. But what an engine! Well ... at least in my opinion
.
