Rather than the usual V-8, we ran this cam test on a…….

By Richard Holdener

The usual situation is we find some unsuspecting V-8, either from the local Pic-a-Part or something we gathered together the necessary parts to build, then test a ton of performance parts. This works well, but the problem with such an approach is that man does not live by V8s alone.

Contrary to popular belief, manufacturers offered vehicles with engine combinations offering less than eight cylinders. Case in point, Chevy sold literally a ton with V6 power, both as a base engine with V-8 options and as the top of the line in applications like the S-10 truck, Blazer, and Astro van. Simply that the engine existed was reason enough to want to improve the power output, but that the 4.3L V-6 was produced in such numbers merely cemented the decision. Toss in the fact the little V-6 was essentially a small-block Chevy missing a pair of cylinders and you have what’s called a moral imperative.

The question now isn’t so much should we upgrade the little V-6, but what should be our first step?  Obviously, we first had to choose a suitable candidate, after all, the 4.3L was produced for nearly 30 years, from 1985-2013. Available in a variety of different configurations and factory power ratings, we chose a 2002 version that offered a number of desirable features, including a balance shaft, free-flowing Vortec heads, and even factory roller rockers, similar in configuration to those on the LS V-8 engine family.

Our thinking was that if we were going to keep most of the motor stock, why not get the best stock parts we could. The Vortec heads offered the best flow of any of the factory offerings, and we liked the fact the balance shaft combo greatly reduced the vibrations inherent in a V-6 configuration. Though the 2002 model was offered in fuel-injected form, we chose to run it with more user-friendly carburetion.

Prior to testing, the 2002 4.3L V-6 was rebuilt to ensure it was up to the stress of the dyno. Though we’ve had great success with our many junkyard adventures, we wanted to give this V-6 a new lease on life. It was rebuilt with fresh rings, bearings, and gaskets from Fel Pro, but the 3/4 small block also received a .030 over bore and a new set of replacement pistons. The Vortec heads were also given the once over, with a valve job, surface, and new seals before we installed a set of 26915 (beehive) spring upgrade from COMP Cams.

Some enthusiasts fear the complexity of the balance-shaft motors, but assembly was no more difficult than lining up the dots on the factory timing chain. The one area we feel we missed out on was the exhaust, as the lack of available V-6 headers (from our usual sources) led us to retain the factory cast-iron exhaust manifolds in testing. Long-tube headers would certainly unearth additional power, but our cam test was run with the stock stuff.

The long block was all but stock, including the stock hydraulic roller cam, but as indicated previously, we did make changes to the induction system. Off came the problematic factory fuel injection, replaced by a simple, but effective, four-barrel carburetor. Edelbrock supplied both the four-barrel Performer intake designed specifically for the revised intake bolt pattern employed on the Vortech heads, as well as a matching 500 cfm Thunder Series carburetor.

To run the carbureted induction system, we also swapped out the computer-controller distributor for an MSD unit. The billet distributor was run in conjunction with a 6AL ignition amplifier. The one problem we encountered while testing was the outer portion of the factory damper spun itself off the inner during one of the dyno pulls. We replaced the stock V-6 damper with a neutral-balance V-8 damper from Speedmaster.

Run on the dyno with the new COMP cam, the power output soared to 251 hp at 5,200 rpm and 298 lb-ft of torque at 3,500 rpm.

Though we had everything needed to make our little V-6 run on the dyno, we didn’t yet have the ability to significantly improve the power output. The missing link in our performance chain was a new cam profile, but first we had to run the freshly rebuilt motor with the stock cam. After a few break-in cycles, the carbureted 4.3L V-6 responded with peak numbers of 207 hp at 4,700 rpm and 287 lb-ft of torque at 2,800 rpm, though we suspect this torque number was an anomaly, as it occurred at the initial load-in point. Regardless, the V6 was happy, if not powerful with the mild stock cam.

4.3L V6 Cam Test-Stock vs COMP 280HR
It is pretty obvious from the dyno results that the 4.3L V-6 was desperately missing the right camshaft. Run with the Edelbrock intake, carb combo, and stock cam, the 4.3L produced 207 hp at 4,700 rpm and 287 lb-ft at 2,800 rpm. After installation of the 280HR cam from COMP Cams, the power output jumped significantly to 251 hp at 5,200 rpm and 298 lb-ft at 3,500 rpm.

To improve the situation, we installed a 280HR grind from COMP Cams design for the later balance-shaft motors. The 280HR offered .525 lift, 224 degrees of duration, and a 110-degree lsa. Equipped with the new COMP cam, the power output of the V-6 jumped to 251 hp at 5,200 rpm and 298 lb-ft of torque at 3,500 rpm. Forty four horsepower (peak to peak) is an impressive amount, but even more so when you look at it as a percentage of the original 207 hp (more than 21 percent). I guess the missing link in this 4.3L was a real camshaft!

Sources:  COMP Cams, compcams.com; Edelbrock, edelbrock.com; Lucas Oil, lucasoil.com; MSD, msdignition.com; Speedmaster, speedmaster79.com