Chevy II Nova Gasser: 496 Big Block Engine Build
As we’ve been planning our Week to Wicked Nova build, we’ve been trying hard to create a period-correct car. As we’re choosing parts, we constantly defer to an imaginary 20-year-old kid in the late 60’s who’s trying to build a potent street/strip car. Something that he could be competitive with at the local drag strip, then cruise down main street on Saturday night.
So what engine would our hero have chosen? Well, after 1965, the new big block was the baddest thing to wear a bow-tie. So, we chose to follow the time-honored hot rod tradition of stuffing the biggest engine available into the compact car inherited from grandma, then hitting the streets, bound for glory.
In our case, we knew that there was a 454 sitting in a grungy heap at Speedway Motors Racing Engines. After a little pleading with shop boss Zach Woods, the engine was ours. The engine shop crew disassembled the engine and stored away just about everything that wasn’t the block and main caps. The block was align-bored with ARP studs, bored to 4.310", and then torque plate honed, all using state of the art Rottler CNC equipment.
The balanced rotating assembly consists of a SCAT cast steel crank with a 4.25” stroke, SCAT forged 4340 I-beam rods, and Icon forged pistons with a 38cc dome. With 136cc chambers, that works out to an 11:1 compression ratio. This all adds up to 496 cubic inches, and we love the subtle nod to a period-correct 396, but with a hundred extra cubes.
Zach was a little conservative with the cam selection since we wanted to be able to drive this car on the street. He selected a Comp hydraulic roller with 242/248 degrees of duration at .050” and .540”/.560” of valve lift with 1.7:1 PRW rockers.
It was important to us that this engine was something that almost anyone could duplicate with a reasonable budget, so we used rectangle port FloTek heads straight off the Speedway Motors shelf, with no fancy port work or mods. Out of the box, these are stout heads, with 320 cc runners and 2.250"/1.880" stainless valves.
We could have been sensible and used a single-plane, single carb intake, but there’s nothing sensible about a gasser. With that in mind, we chose a Weiand tunnel ram and two 650 cfm Holley 4150’s. With these goodies bolted on and the engine still hanging on the stand, we almost needed a step stool to hook up the linkage. Cool.
What about those valve covers? Those are special. In case you didn’t know, there’s a huge and very impressive museum attached to Speedway Motors called the Museum of American Speed. It’s filled to the rafters with vintage engines, race cars, and automobilia. They have a few parts set aside to be used by their restoration crew, and we spotted these valve covers on the shelf next to about a thousand vintage carburetors. They are NOS, still in the box Cal-Custom die-cast pieces with a period perfect black wrinkle finish. After a little begging, we were allowed to take them out of the archives and bolt them to an engine for the first time in fifty years.
And now for the moment of truth. The engine looked the part, but what kind of power would it make? The first pull was conservative, and Zach lifted at 5,500 rpm. Even so, we were pleased to see 632 horsepower on the screen. After some tweaks to the timing curve and a change to 67 primary/70 secondary jets in both carbs, our final pull netted 646 horsepower at 5,800 rpm and 656 lb/ft of torque at 4,800. Should move our little Nova around pretty well.
Car Craft editor Johnny Hunkins and contributor Rocky Rotella were there for the build, so you can look for a full feature on carcraft.com. Also, be sure to follow our Week to Wicked build the week of August 12th-16th. That’s when we’ll stuff our 496 into our little Nova and really make some noise.