Camshaft technology has come a long way, especially when it comes to Mopar camshafts. Early aftermarket cams for Mopars were designed generically to fit any application, not taking advantage of the Mopar’s larger .904 diameter lifter size. Luckily, Comp Cams recognized that with the larger diameter lifter that a more aggressive ramp rate could be used, getting the valve open quicker and allowing more air and fuel into the cylinder. Utilizing this concept, a camshaft with very mild specifications can make significantly more power than a stock or early aftermarket cam with similar specs. For our 383, we chose a Comp Extreme Energy hydraulic flat-tappet camshaft with .477 intake and .480 exhaust lift, and 268 and 280 degrees of advertised duration respectively. This cam has nearly the same specs as the cam we’re replacing, with only slightly more lift and duration, but takes advantage of Comp’s modern lobe design and has a wider 110 degrees of lobe separation.

Important Numbers
RPM x1000 hp ft-lbs
2.80 154.01 288.88
3.00 173.99 304.60
3.20 188.71 309.72
3.40 203.60 314.51
3.60 213.97 312.17
3.80 223.83 309.36
4.00 231.73 304.27
4.20 240.43 300.67
4.40 244.93 292.37
4.60 244.00 278.59
4.80 240.62 263.30
4.60 -INF -INF
4.40 -156.38 -186.66

Changing the camshaft in a big-block Mopar is fairly straightforward, and can be accomplished without much trouble with the engine still in the car. We recommend replacing the timing chain any time you’re in this part of the engine, and we chose to replace our entire stock-style timing set with a Comp double roller unit. The lifters must also be changed any time the camshaft is replaced, since lifters establish wear patterns to the individual cam lobes. Failure to replace lifters or swapping lifters from lobe to lobe will certainly cause premature wear, and can round off a cam lobe quickly. We picked a set of Comp’s Pro Magnum hydraulic lifters to match our Comp cam.

It’s also a good idea to check piston-to-valve clearance any time you install a cam with more lift and duration, unless you’re quite sure you have enough room Valve retainer to valve guide clearance is also important to check, and make sure the valvesprings are compatible with the new camshaft. Having previously checked the vital clearances in our engine, we knew this camshaft would work just fine. Additionally, the open and seat pressures of our valvesprings were right in line with the specs called for by Comp, so we didn’t deem it necessary to change valvesprings. If you’re not sure about your engine, however, it is always a good idea to double check all of the critical dimensions and match the valvesprings to the camshaft being used.

Replacing the cam while the engine was in our C-Body required removing the radiator and air-conditioning condenser, but otherwise no special tools or techniques were required other than a puller for the harmonic balancer. All told we had our cam swap completed in a day’s work, and ready for dyno testing on our Dynojet chassis dyno. We decided to test our car after the cam swap, and then install an Edelbrock intake and carburetor to see how those parts would also help our combination. Remember that simply swapping a camshaft might not benefit the engine as much as you’d expect if the engine isn’t getting the air and fuel required to make it perform properly.

On the chassis dyno, we made a first pull and picked up some 18 horsepower with the cam swap alone. Torque was up as well, but not as much as we predicted. So we bolted on our Edelbrock Performer RPM dual-plane intake manifold and 750-cfm Edelbrock Performer Carb. The addition of these parts really enhanced our camshaft swap, and power was up by 22 horsepower at peak, to 245.44 from 223.91, with great gains across the board. Torque was up as well by more than 17 lb-ft at peak with across the board gains throughout the rpm range.

Results
Baseline | cam only | cam/intake/carb
Horsepower 223.91 241.41 245.44
Torque 298.55 307.64 315.73

Remember that these numbers are at the rear wheels, and some 30 to 35 percent lower than what would show on an engine dyno. Also remember that this is a stock, low compression engine so we don’t expect it to be a true powerhouse. Even so, more than a 10 percent gain in horsepower for a day’s work is not too shabby. Better yet, our Newport is now even more fun to drive. Be sure to check out moparmuscle.com for all of the details of our testing, and to see video of the big Chrysler on the chassis dyno. mm

SOURCE
Edelbrock (Carbs)
800-416-8628
http://www.edelbrock.com
Comp Cams
3406 Democrat Rd
Memphis
TN  38118
800-999-0853
www.compcams.com