The Leaker: 470 HP For $2,350Our first scheme was by far the most pure: Make big power and keep it cheap by bolting speed parts to the engine that came out of our Nova, reusing all the critical hardware and stuff. That fell apart when the Nova mill was too grimy to clean up in time for the deadline. We cheated by using a short-block you may remember: It's the 350 from our El Cheapo '72 El Camino, and it had gone high 12s on nitrous. The last place to assemble this thing was Chevrolet, so it was totally legit.
We were geniuses up to the point that the valve-to-piston clearance was nonexistent. The Dart heads are milled to such an extent that the edges of the intake valves stand proud above the deck surface, whereas a stocker might be sunken into the chamber by 0.060 to 0.100 inch. This takes up valve-to-piston clearance quickly, especially when the valve sizes are 2.050/1.600 and you're cramming them into stock cast pistons with undersized valve reliefs that are in the wrong places.
We consulted Lunati for a cam that would work with limited valve-to-piston clearance but still meet our 7,000-rpm goals. The best fit was PN 40115, an older cam with slower ramps. The area of least valve-to-piston clearance was within 10 degrees on either side of TDC, with the cam at about 0.250-inch tappet lift. Therefore, we needed a cam with steep duration at 0.050 but not too aggressive at 0.200 to 0.250 inch. The Lunati 40115 is a solid flat-tappet with 259/268 at 0.050 on a 106-degree lobe separation angle and just 0.519/0.531-inch lift and a loose 0.030 lash setting.
But it wasn't enough. We needed more valve-to-piston clearance, so out came the die grinder and a carbide bit to whittle aluminum off the top of the pistons with them still installed in the engine. Stock cast-piston tops are roughly 0.350-inch thick, and we maintained the depth of the stock valve reliefs but made them much larger. Butchery, to be sure, but it works, and we'd have even felt OK about throwing a 150 shot of nitrous on top of them.
By the time we were done, we figured we'd enlarged the 12cc dishes in the stock pistons to 13 cc's. The pistons were 0.032 inch below the deck surface of the block, robbing precious compression ratio. Some of that we regained by using Fel-Pro steel-shim head gaskets, which have a 0.015-inch compressed height and 4.100-inch gasket bore as opposed to the common composition gaskets at 0.041-inch compressed height and a 4.185-inch bore. Even with thin gaskets we had a massive 0.047-inch head-to-piston clearance. We would have liked a tighter quench of about 0.037 inch, but the pistons were too deep in the hole. The compression was a depressing 10.77:1. Far better than 8.5:1, but we hoped for 12.0:1.
We took it to the dyno anyway. And you know what? It ran dang good. We topped our conglomeration of used junk and hacked pistons with the small-chamber 215cc Dart heads, an 850-cfm Speed Demon carb, a Mr. Gasket 2-inch open-style carb spacer, and an Edelbrock Victor Jr. single-plane. We used 151/48-inch-tube Flowtech headers (that needed lots of bashing to clear the angle-plug heads) with 18-inch collector extensions, and we tossed in the Nova's grimy HEI-which everyone said would give up at 5,500 rpm-plus some used plug wires. The lump put up a decent 469 hp, pulling hard to 7,000 rpm. The power was so flat from 6,300 through 6,800 that it's tough to quote an exact peak rpm.