We built our 383 from a pile of parts, careful attention to clearances, and a little help from Competition Products and Canfield cylinder heads.
Last month, we produced a giant section on everything you ever needed to know about building a 383 small-block Chevy. The only thing we didn't give you was the buildup itself, because we ran out of room. So here is the engine buildup and dyno test of a typical street 383 that we built with a short-block kit from Competition Products, heads from Canfield, and an interesting flat-tappet mechanical from an upstart cam company called Camshaft Innovations.
The plan was, as always, simple: We wanted to make as much overall power as we could without spending a wad of cash. Our self-imposed rules limited us to no more than $10 per horsepower, so the push was to make as much power as possible, but also to be careful how we spent the rent money. The approach was a triple threat of pump gas compression, a great set of cylinder heads, and an aggressive camshaft. While we've built more powerful 383s than this engine and we've certainly built less expensive ones, we've never built one that made this much power while spending so little coin. The bottom line was a 475hp engine for much less than $10 per horsepower. Check it out.
The Canfield 195 heads came with a 72cc CNC'd combustion chamber, a set of 2.02/1.60-inch stainless valves, and a nice set of dual-performance springs to make sure we had excellent control over the valves. The chamber size combined with the flat-top pistons resulted in an ideal 9.8:1 static compression ratio.
Torque Time 383
If you took all the new crate engines and stacked them up into one big pile, you'd see that many of them sell for roughly the same price as our budget on this 383. The problem is that most of those engines hover around 350 to 400 hp. Our fiscally responsible 383 twirled the horsepower meter past 475 for the same wad of cash. All you have to do is assemble it. We started with a very affordable Competition Products 383 rotator package that relies on a cast, two-piece rear main seal crank, stock 5.70-inch rods with ARP bolts, and Speed-Pro hypereutectic pistons. We rounded up a good 350 block that JGM cleaned and machined with a 0.030-inch overbore, and after a careful assembly, we had a reliable 9.8:1-compression short-block ready for the rest of the power equation.
We employed the Competition Products catalog again to choose a Howard's flat-tappet hydraulic cam with a reduced base circle to help connecting-rod clearance. We also decided to go with a pair of 195cc Canfield aluminum heads. Canfield owner John Fenton suggested a second cam from Jay Allen, who owns a company called Camshaft Innovations. Allen prescribed a more aggressive flat-tappet mechanical grind that appears at first to be a much bigger cam. However, it's not accurate to compare a flat-tappet mechanical cam with hydraulic cam specs even at the 0.050-inch tappet-lift numbers. The reality is that a mechanical cam includes a clearance ramp designed to use duration to gradually close up the hot lash clearance, which requires several degrees of duration to accomplish. A shortcut to make the comparison between hydraulic and mechanical cams more accurate is to subtract 1/2 degree of duration at 0.050-inch tappet lift for every 0.001 inch of valve lash. Given this cam's 0.016-inch lash spec, we subtracted 8 degrees from the 0.050-inch duration numbers. This places the Camshaft Innovation cam at 237 degrees at 0.050 rather than 245 degrees. Allen also designed the cam with a softer acceleration rate to accommodate a more aggressive 1.7:1 rocker-arm ratio. The more radical rocker ratio puts the gross lift close to 0.600 inch, which is roller cam territory at a flat-tappet cam price.
After Jim Grubbs Motorsports cleaned, mag'd, and machined the block, we set the crank in place and checked for endplay. Endplay measured between 0.005 and 0.010 inch. We also spent considerable time ensuring our bearing clearances were correct. We set both rods and mains at between 0.0023 and 0.0028 inch. | 
The connecting rods were already installed on the Speed-Pro hypereutectic pistons, so all we had to do was clean everything and install the moly 5/64-inch ring package. We used the recommended ring expander rather than spiral the rings in place. |
Tapered ring compressors are the only way to fit the piston and ring package into a cylinder. We've actually broken rings when using universal ring compressors. We also used a set of aluminum ARP rod-bolt extensions to protect the crank. | |