ZR1

ZR1

The first ZR-1 Corvette was 1989-1995, and I think was the 32-valve double-overhead-cam V8 designed by Lotus and assembled by Kiekhaefer (“KEY-kay-fur”), the builder of Mercury outboard-motors.
It wasn’t an offshoot of the vaunted Chevrolet Small-Block, but was rather a ground-up redesign. It also was aluminum, and I think the Small-Block was still cast-iron.
The new ZR1 is the Small-Block redesigned yet again, although little is left of it since introduction in the 1955 model-year.
About all that’s left is the basic architecture: bore-centers 4.4 inches apart.
The motor is also cast-aluminum, and long-gone are the siamesed exhaust ports, replaced by port-order similar to Ford: intake-exhaust, intake-exhaust, intake-exhaust, intake-exhaust versus exhaust-intake, intake-exhaust, exhaust-intake, intake-exhaust.
This equalized the heads and porting for each cylinder, and can equalize fuel-charge with fuel-injection.
Over a V8, carburetion could make end cylinders run too lean, and center cylinders too rich. (Carburetion is also sloppy.)
But it’s still two valves per cylinder with valves operated by pushrods and rockers.
A four-valve head would breathe better, but would upsize the engine package and probably make it heavier. Four-valve heads and overhead cams also cost a lot.
So the Corvette continues with a two-valve head, and to make it generate 625 horsepower they supercharged it.
It’s a variation of the old Callaway twin-turbo trick.
They tried twin-turbos at first, but their test-mule caught fire and burned to the ground. —Back to the drawing board.
So what we have is a belt-driven Eaton Rootes supercharger nestled between the heads, more-or-less the same principle that supercharges fuel dragsters.
Force-feed a two-valve head and it breathes like a four-valve head. (One wonders about force-feeding a four-valve head, an idea ya see in motorcycle drag-racing, but it was ruled illegal in car drag-racing.)
So 200+ mph. Where do you get that kind of speed other than in the desert — or perhaps a racetrack?
My dentist saw I was reading a Car & Driver Magazine article about it and said “ya gonna get one?”
“Are you kidding?” I said. “Where do I put the dog? Where do I put the groceries?”
It’s only 6.2 liters, but that’s 100 horsepower per liter. Estimated base price is 100,000 or more smackaroos.
They should be hogging out and supercharging the NorthStar.
The Chevy Small-Block was revolutionary in its time, but engine design has leapfrogged it.
Recent inline four-cylinder motorcycle engines sound better than the original Formula-One Ford Cosworth V8.

The “Chevrolet Small-Block” V8, introduced in the 1955 model-year at 265 cubic-inches, was a breakthrough design that put everything else on-the-trailer, and prompted copy-cats. I went through various enlargements, first to 283 cubic inches, then 327, and finally 350 cubic inches. It was also produced in other displacements — like 302 cubic inches for Trans-Am racing. The basic architecture is still in production.

Callaway, of Old Lyme, Conn., is a specialized manufacturer of hot-rodded Corvettes available through affiliated Chevrolet dealers.