The Chevrolet 1-ton dualie pickup has always been a symbol of power. With its monstrous hood and huge dualie wheel humps, the truck just grunts power like a sliver-back gorilla. Looks can be deceiving, however, and in the late '70s to mid '80s even the big-block dualies lacked enough power to back up their monster image. Most of the problem came from Big Brother's slapping emissions restrictions on the trucks, and our '82 test brute was no exception. Granted, when Editor Cole spotted this truck and shelled out a diminutive $2,500 for it, he almost got the deal of the century. But these big trucks are for hauling project cars around, and this one's big-block had just about hauled its last bail of hay.
Our dualie's big-block would...
Our dualie's big-block would breath better and grunt out tons more power with some new Edelbrock and Crane engine components. We also used new hardware from ARP and a complete gasket kit from SCE.
Plans were quickly made for a brute force upgrade centering on increasing the truck's torque output in real street rpm. So the dualie was driven into the newly open-for-business McMullen Argus Tech Center where it was first subjected to a rigorous day's lashings on the mighty Dyno-Jet chassis dynamometer.
Since the dualie's big-block was bone stock and dead tired, it didn't take long to find maximum horsepower. At the rear wheels the truck actually made some impressive torque for such an old beast. It had no trouble cranking out 324 lb-ft of torque at a very low 2,600 rpm. This meant that the 454-cid Rat under its hood was still up to the task of hauling a heavy load. Unfortunately, peak horsepower really fell short of respectable because the big-block could barely muster 190 ponies at 3,900 rpm. Keep in mind that these figures are at the rear wheels and calculate at bare minimum a 25 percent correction factor for power loss through the giant two-piece drive shaft and 14-bolt rearend. If you do the math, this 454 was actually making almost 250hp and 400 lb-ft of torque. Yet, those were hardly numbers for a big-block to be proud of, so a call was made to Edelbrock for some suggestions.
Any time you're removing tubes...
Any time you're removing tubes and wires from the engine, it's best to label them as they come off. Yes, we know that's a tedious process, but the effort will payoff if you have to wait weeks to reassemble it.
Edelbrock's technicians informed us that big-blocks of this truck's vintage usually employed flat-top or even dished pistons, and our Rat could suffer from really low compression if we swapped on a pair of Edelbrock's aluminum heads with 110cc combustion chambers. Thankfully, Edelbrock has thought of a way to avoid this potential problem and offers a special 100cc "high-compression" head just for big-blocks with pistons like these. While this head will not actually squeeze much more compression out of our big-block, it will keep it around 8.5-9:1, which is just right for a towing monster on pump gas. So the decision was made to order a set of Edelbrock's High-Compression Performer heads from Jeg's High Performance Warehouse.
We figured that since we were using Edelbrock heads, we might as well include most of the Edelbrock Performer line of components also. So we added to our order a Performer 2-O intake manifold, a 795-cfm Performer Q-Jet carb, and some 2-inch primary-tube Hedman headers. Unfortunately, the Edelbrock Performer series camshaft was too big for our dualie's towing needs, so we chose a Crane PowerMax H-260-2 hydraulic cam and lifter kit. We also ordered Crane's replacement pushrods and some new Blazer aluminum roller rocker arms with a standard 1.7:1 big-block ratio. And since this power bolt-on bonanza wouldn't be complete until after a trip to the muffler shop for installation of true, dual exhaust with a crossover, we also ordered some Edelbrock 409-series stainless Performer RPM mufflers.