The crankshaft is one of Scat's high-quality 9000 series units that the Heath team trusts more than a high-mileage stocker. The connecting rods were carefully checked for any flaws, heat-treated, fitted with new GM bolts and bushings, then brought to factory dimensions. The cylinder walls were sized to Heath's specs to provide a piston-to-cylinder wall clearance of .0057 inch with a super-fine wall finish. The pistons are Mahle standard compression height replacement units treated to Performance Coating's Tri-Coat process. They were set to factory specs (.006 inch out of the hole). This, combined with a .045-inch Cometic multilayer steel gasket, delivered a stock compression ratio of 21.3:1.
Heads and Valvetrain
The factory issued 6.5L heads on this engine were outfitted with larger valves, as used in the '82 6.2L J-code engine. Other than machine work necessary to fit the valves, the heads are bone-stock-no port or runner work of any kind. Valve stem clearance is on the tight side of GM's spec range at .001 inches on the intakes and .0012 inches on the exhausts. The entire valvetrain, including the sprockets and chain, camshaft, followers, pushrods, rockers, springs, retainers, and seals are stock. The intake manifold is a stock, unaltered unit from the L65 heavy-duty 6.5L engine.
Fuel Injection
The fuel injection pump is an out-of-the-box stock Stanadyne DS-4 5521. The injectors are Heath's own high-output units. The fuel lift pump is a special version of the AirDog, with delivery pressure reduced to 7 psi. The computer programming is Heath's GL4 series with a higher rpm limit. The GL4 is supplied to customers with a 3,700rpm limit. The program used in the Bonneville racer is altered to rev to a limit of 4,150 rpm.
Turbos and Water Injection
The only areas of the engine that were radically modified are the custom tube-type headers and turbochargers. The headers were fabricated from .125-inch wall DOM tubing and coated by Performance Coatings. The turbos were engineered by John Todd of BD Diesel Performance, and are based on non-wastegated Garrett turbo models. The truck was outfitted with Heath's computer-controlled Water-Mist injection system for intercooling. The truck is restricted by class regulations to diesel and water. No nitrous, propane, or methanol are allowed.