Almost as many camshaft options are available, as there are opinions as to which profile offers maximum performance. For this application, we're more interested in torque than horsepower, and that limits the field to cams with relatively short duration and tight lobe separation. As a means of minimizing idle quality degradation, the cams for LS and other late-model engines are commonly ground with 114 degrees of lobe separation. Since we were working with short duration specifications, idle quality wouldn't be much of an issue, so we tightened the LSA to 112 degrees. Combined with an intake duration of 208 degrees and exhaust duration of 214 degrees (at 0.050 inch lift) this cam would theoretically put a nice bump in the torque curve-especially considering its 0.554 inch intake and 0.559 inch exhaust lift.

Unfortunately, things in magazine land are about like they are in your garage or on the racetrack; they don't always turn out as planned. When we reintroduced the truck to the rollers at Atlanta Chassis Dyno, horsepower was up significantly, but torque increased only 5 lb-ft. (More details below.)

Our selection of cylinder heads wasn't quite as straightforward as our cam choice. According to Vmax Motorsport's Pete Incaudo, the most economical option for a towing engine-aside from leaving the original heads unmolested-is pocket porting and a multi-angle valve job. However, we had a pair of Vmax Motorsports CNC-ported LS1 cylinder heads on hand for another project that never materialized, so we figured "why not?" They had already been angle milled and their combustion chambers measured 60cc, the same as original equipment 5.3L heads.

Ironically, before the advent of LS6 cylinder heads, a popular option was to install 5.3L truck heads on 5.7L Camaro and Corvette LS1 engines as a low cost means of increasing compression ratio. (The ports in the truck heads are virtually identical to those in LS1 heads, requiring only the replacement of the 5.3 heads' 1.89 inch intake valve with an LS1 2.0 inch valve for equivalent airflow capacity.)

Used cylinder heads for 5.3L truck engines are readily available at reasonable cost, so if you don't want your truck apart for as long as it takes to get the head work done, you can buy a pair of used 5.3L heads and have them prepared and ready to install before removing the original heads (which you can subsequently sell). Irrespective of the castings you select, keep in mind that 5.3L engines have a 3.78 inch bore diameter, which limits maximum valve diameter. Valves larger than those used in stock LS1 heads (2.0 inch intake, 1.55 inch exhaust) will be unceremoniously introduced to the top of the block.

Valvesprings are another component of the camshaft/cylinder head equation that can lead to long, sad stories if ignored. Many aftermarket camshafts open the valves in excess of 0.500 inch which will put stock valvesprings into coil bind, as was the case with the cam we used. To accommodate cam lift, we installed Comp Cams 26918 beehive springs, which can be used with cams having up to 0.600 inch lift.

The final modification in our quest for increased performance was the installation of a Vmax Motorsports CNC-modified throttle body in place of the less glamorous original version. Even though throttle bore diameter is unchanged (it wouldn't make sense to enlarge it because that would make it larger than the opening in the intake manifold), the CNC modifications recontour and smooth the entry, and that delivers a significant airflow increase over the entire rpm range.

After installation of the cam, heads and throttle body was completed, we did some testdriving before returning to the dyno. One of our concerns was that the stock injectors didn't have a high enough flow capacity for the engine's higher air processing capability. A few wide-open throttle blasts, confirmed these suspicions, as injector pulse width above 5,000 rpm was excessive.