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.
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.
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.
All that was left to track down now was a high-performance ignition upgrade for the worn-out HEI under the hood. MSD suggested its four-pin HEI computer module and all the parts we'd need to rebuild the distributor including a new coil, a cap, a rotor, and wires. After a hard weekend's work under the dualie's hood and a day at the Muffler Man exhaust shop, we pulled it back into our Tech Center to see what it could muster. Before dynoing the engine, Editor Cole did comment that the truck pulled much harder than before and that now it sounded great! He felt confident that future mileage tests would also prove that the increase in power would yield an increase in efficiency, and the truck still wouldn't pollute any more than it did when it was new.
So we put the dualie through another day's bashing on the Dyno-Jet and found that both power and torque increased a significant amount-not incredible numbers for a motor destined to do street/strip duty in a Camaro or Chevelle, mind you-but for a tow vehicle intended to cart around numerous project cars on a large, two-axle trailer, it was a good jump in both power and torque. Additionally, the best test, the one often referred to as "seat of the pants," yielded an impressive driving experience proving that big numbers don't always translate into real-world drivability.
As for the results on the Dyno-Jet, both power and torque grew with the torque peaking at 400 lb-ft (an increase of 76) at 2,500 rpm, while the horsepower output rose to 280 ponies (up by 92) at 4,400 rpm. What the computer printouts confirmed was that the torque came on low and stayed there throughout the whole rpm range, providing this vehicle with the necessary motivation to get the job done.
And, as a final assessment of this Edelbrock swap, the additional cooling that the combination of a trick aluminum waterpump and lightweight heads will provide means that on those long trips towing a project to the paint or chassis shop, we won't get stuck on the side of the road waiting for the temperature to come down. And, that's a good sign that our own temperatures won't be rising.
Bump And Grunt
The Crane PowerMax cam we chose is designed for towing and good gas mileage. It's not big by any standards, and that should translate to tons of torque with very good wear characteristics for the associated parts like valve springs.
Crane H-260-2 PowerMax hydraulic flat-tappet cam PN 133901 (PN 133902 includes lifters with cam kit)
|Advertised duration:||Int 260||Exh 272 inches|
|Duration @ 0.050:||Int 204||Exh 216 inches|
|Lift:||Int 0.484||Exh 0.502 inches|