A New Roller For The Mauler - Mauler 440 Engine Project

In the initial testing of our Mauler 440 engine project, we had a chance to see how close our selection of parts came to meeting the stout objectives we originally set. The one thing that stood out from that test session was that our combination was overwhelming the capabilities of the flat-tappet hydraulic camshaft we were running. In the quest for the ultimate in fast-acting valve motion, we started with the quickest of the quick .904-inch flat-tappet profiles, and then goosed the rate to an unheard of speed with a set of 1.7:1-ratio rocker arms. As flat-tappet hydraulics go, it was intense, reaching .600-inch lift with a short 231 degrees of duration at .050-inch lift. As our testing showed, the fast rate had the potential to make the number, but the effort was hampered by the ability of the lifter's hydraulic mechanism to cope with such aggressive action. The simple solution was to move to a solid street roller.

When very quick valve action is the goal, a solid roller is the conventional choice. Fast valve action is precisely what this type of camshaft configuration is created for, and we had no doubt that the setup would work. Being a solid design, any question of hydraulic instability would be moot, since there is no fluid mechanism to foul. The roller allows much higher-rate valvesprings to be run without the risk of wiping the cam or lifter face due to overloading. With the flat tappet used in the previous test, we had pushed the spring loads to the limits of what we'd gamble with-at 377 pounds of pressure over the nose, it was a gamble. With a roller cam, spring loads in the range we'd need for control would not be an issue. We could have made another play at finding a magic spring combo for our hydraulic flat tappet, but by changing to the roller, all of the problems with operating the valves in our combo would be solved in one swipe.

The Cam
We were still aiming our effort for street use, so our lobe shopping was focused on the Xtreme Street Roller lobes in Competition Cam's line-up. Our hydraulic flat tappet measured 231-degrees duration at .050-inch lift. Since we were moving to a solid profile, we needed to go with a cam larger in duration, as measured at .050-inch tappet rise to make up for some of the loss of duration at the valve created by the lash. A rule of thumb is, a solid cam with 8-10 degrees more duration than the flat tappet will approximate the .050-inch duration number of a hydraulic, once the lash is taken into account. With a little greed in our minds, we settled on just a little more than that, selecting lobe numbers 4874/4875, stretching the duration to 242 degrees on the intake, and 248 degrees on the exhaust. These street roller lobes would blow away the lift we were able to achieve with the flat-tappet cam, opening the valves to a full .646 inch on the intake, and .653 inch on the exhaust, when combined with our aggressive 1.7:1 rocker ratio. The high lift would also play well with the high-lift airflow capabilities of our Indy CNC 295 EZ heads. With all the extra air up for grabs by just tipping the valves open a little further, it makes sense to tap into the potential. As with our hydraulic grind, we had the camshaft ground on a wider 112-degree lobe separation angle, a move that will help bleed some low-rpm cylinder pressure with our high-static compression ratio, and help to improve idle quality and vacuum.

To go with our cam, we ordered a set of Comp's (PN 829-16) solid roller lifters. These Comp lifters drop right into a production big-block Mopar with no modifications to the block or oiling system required. The correct pushrod length for the solid roller is different than what is used with a hydraulic flat tappet, so the required length was found by mocking up the combination with a length-checking pushrod. Custom pushrods were ordered from Smith Brothers. To provide valvetrain control, selecting an appropriate spring is vital. The spring seats in the Indy heads are machined to 1.550-inch diameter, so that set the spring diameter spec. We looked no further than the Comp Cams spring chart to find PN 999-16. These are an H-11 tool steel spring set, which delivers 196 pounds of load on the seat at an installed height of 1.900 inches, and 608 pounds at .650-inch lift. With that kind of spring load, we would easily cover any question of valve control with our combination. To go along with the springs, we selected Comps' (PN 732) titanium retainers, and (PN 611) 10-degree SuperLocks to fit the single groove 111/432-inch stems of the Indy valves.

There are a few other considerations when making the swap to a roller cam. All roller cams feature the three-bolt front nose, as factory fitted in Six Pack 440s. Our hydraulic cam was ground on a conventional single-bolt core, so we need to upgrade the cam drive to a three-bolt style. We went with Comp's top-of-the-line, billet-steel, adjustable timing set, (PN 3125 KT), which features a hex adjustment eccentric at the indexing pin. The adjustable timing set allows the cam phasing to be infinitely adjusted +/-6 degrees by simply loosening the three mounting bolts on the cam gear, and turning the adjusting eccentric with an Allen wrench. The adjustability makes it easy to degree-in the cam to an exact setting, and also greatly facilitates cam-timing changes on the dyno when dialing in the combo. To make changes to the cam timing even easier, we modified our stock timing cover with a cam access plate. A roller cam installation in a big-block Mopar will require a thrust button to control forward cam thrust. We handled that with a Comp Cams (PN 206) nylon button.

The final item to address is the distributor drive, since roller cams are ground on steel billets, making them incompatible with the factory steel drive gear. A Milodon distributor drive with a bronze gear had us covered there.

The Dyno
With our 440 re-assembled, it was time to quantify the value of our mods on the dyno. We intended to start with the ported Indy 2D two-plane intake manifold, topping the engine with the same Demon 850 carb we had run in the previous test session. Unfortunately, our 2-inch Hooker SuperComp headers were not available to us on test day, but we did have a set of tti 2-2 1/8-inch step headers at Westech's dyno facility. We had tested these two headers back-to-back in a previous test, and found the results very close on a 650hp, 452-cube RB. Upon firing and warming up the engine, we detected a problem in the ignition system, which was traced to the magnetic pick-up in the distributor contacting the reluctor in the Mopar distributor. With the distributor damaged, we made an expedient change to a MSD distributor, which also required changing the right side valvecover for clearance. We would not expect the distributor change to have an effect on output.

With the bugs worked out, it was time for some power runs. The engine was run at a static pull to access the air/fuel ratio, and the jetting was adjusted as required. Satisfied with the jetting, we moved on to a timing loop and, surprisingly, found best power at an indicated 39-degrees of advance. How much power? Pulling the engine from 2,500-6,700 rpm, peak horsepower came in at 632 hp at 6,300 rpm, a gain of 72 hp over the best observed with this induction combination in the previous test session. The solid roller did exactly what it is supposed to do, applying controlled motion to the valvetrain, extending the power curve by allowing the engine to continue making power higher in the rpm range. While the power gain was remarkable, torque was remarkably broad, topping the 500-lb-ft mark at just under 3,000 rpm, reaching a peak of 565 lb-ft at 5,300 rpm, and remaining above 500 lb-ft through 6,500 rpm. Torque, torque, and more torque everywhere on the curve. We were impressed.

Looking to edge up the peak power figure still further, we installed a Wilson 1-inch tapered spacer under the carb. Typically, a spacer will help a dual-plane intake in the upper reaches of the rpm range, at the expense of some torque at the bottom end. The object is to try it and see if the trade is worthwhile. The tapered spacer showed its merit at the top, edging power up to 640 hp, at the same 6,300-rpm peak. Interestingly though, torque very low in the rpm range was indeed sacrificed, but by 2,800 rpm the loss was recovered. In practical terms, loss that far down in the rpm range probably wouldn't be missed, since even a mild 11-inch torque converter will put the engine above that rpm range right off the line. A spacer makes sense, if hood clearance will allow running one.

We were very satisfied with the results shown by the 2D Indy intake, and in the operation of the Comp Street Roller camshaft. The engine idled at over 12-inches of vacuum, despite the more radical cam specs, and the airflow numbers showed cam/valvetrain combo stable at 6,800 rpm, the highest rpm level the engine was run to. While 640 hp was a very satisfactory peak, we still had the Indy single-plane manifold to try. The Indy intake is a race-style high-rise single-plane, with a runner and plenum design that is very well suited to high-rpm output. We expected to see an increase at the top end with this intake. True to form, the single plane unlocked a healthy amount of hidden power up top, raising the bar to 655 hp at the same 6,300 rpm peak as the two-plane, for a 15hp advantage, peak-to-peak.

Looking at the torque curve showed that the single-plane actually unleashed more peak torque than the dual-plane, topping 578 lb-ft. The single-plane showed a solid gain in both the torque and horsepower peaks, but that's not the whole story. From 2,500-4,300 rpm, the dual-plane produced more torque. At 2,800 rpm, the dual-plane held an advantage of over 50 lb-ft. By 4,300 rpm, the single plane caught up, and kept going for a higher peak number, and kept the edge. Interestingly, rather than dropping off, the torque curve generated by the two-plane tracked virtually identically up to the top of the rpm range with the single plane, just a little behind in torque production. The gap actually narrowed towards the very top of our test.

The Mauler 440, at 655 hp, is making quite a bit more power than we originally intended from this build, due in large part to the awesome power potential of the CNC Indy cylinder heads. Torque, at 578 lb-ft, is a little short of our admittedly ambitious original target of 600, but the curve is much broader than we expected. Part of that is the result of the somewhat wide 112-degree lobe separation angle, which will typically shave some of the peak torque and broaden the torque curve.

What's next? We really should drop this monster in a car, but we are toying with further modifications to see what other fun we might have with a basic 440.

Dyno Results
Superflow 902 Engine Dyno
STP Correction
Tested At Westech
446 RB Mopar

Legend
T1. Indy two-plane intake
T2. Indy two-plane intake with a Wilson 1-inch tapered spacer
T3. Indy single-plane intake