HOT ROD to the Rescue
As originally built back in 2006, this 1969 Plymouth Road Runner clone was powered by a thumping 11.3:1, Chrysler 440-based engine, bored 0.040-over, and equipped with a 4.15-inch-stroke crank to yield 496 ci. Since then, the engine had been refreshed at least once before present owner Ray Lane got his hands on it in 2012. The Plymouth had laid dormant for several years with a reputation for breaking rocker arms, an annoyance that persisted under Lane’s stewardship.
Enter Chicago-area rescuer, Westech Automotive’s Norm Brandes. Initially, Brandes thought it was a random, oldage-related problem: Like highly stressed aluminum connecting rods, aluminum rockers have a finite fatigue life. Explains Brandes, “I thought the rockers were just cycled out.” He replaced the original shaftmount valvetrain with Dave Hughes shafts, rockers, spacers and shims. Chrysler specialist Hughes is a fanatic about parts longevity and proper valve-
train setup, and his parts have a great reputation for strength and durability. Tune-up ace Brandes also adjusted the valve lash slightly tighter (the owner said it sounded too noisy) and performed a few timing and carburetor tweaks. The car ran great for several hundred miles.
THE FINAL DIAGNOSIS
Two months later, Lane called Brandes back: “I told Norm I was suddenly having engine noise and the engine had a miss. Brandes told me to get the car down to his shop ASAP.”
Brandes picks up, “When the car arrived, we removed the valve covers. The stronger Hughes rockers had held up fine but now two intake pushrods and two valves had bent—the next weak link. Those pushrods had dropped clear down off the adjuster nuts into the valley, and cylinder Nos. 3 and 5 intake valves were no longer opening. Later, talking to Lane, we realized those were the same two cylinders where he and previous owners were breaking the rockers.”
When Brandes removed the driver-side cylinder head, he discovered massive carnage in the valley: The bent pushrods had fallen out of the lifter cup, breaking the lifters in cylinders 3 and 5, gouging the cam lobes, and scratching a cylinder wall. There was debris throughout the motor, but the main and rod bearings and journals were still OK. “Our intervention got to them in time,” Brandes says. “But
we needed some valves, and the one damaged cylinder required overboring, so we’d have to order new pistons.”
But what caused the failures in the first place? Valve-to-piston contact! On a bigblock Chrysler, the center two exhaust ports and valves are adjacent to each other, meaning the intake (I) and exhaust (E) valve order is reversed (I-E-E-I). To match this valve layout, there are two different piston top configurations. It turned out the pistons for Nos. 3 and 5 cylinders had been swapped, causing contact with the intake valve.
THE FIX: PISTONS
Brandes bored and honed the already 0.040over engine another 0.015-inch oversize (0.055-over a stock 440 bore), sufficient to clean up the damaged cylinder while matching the next larger Icon Pistons’ PN IC826 shelf-stocked oversize. Total displacement rose to 499 ci. Icon’s forged pistons were ordered as a complete kit with ductile plasma-moly rings as well as Icon’s optional Line2Line abradable skirt coating. Sprayed onto the piston skirts, the coating’s added thickness develops essentially zero piston-to-
wall clearance for reduced piston rock and quieter operation. During initial engine runin, the coating wear-mates to the cylinder, developing microscopic high/low spots that actually retain additional oil for reduced friction. Icon weight-matched the new pistons to the original set, so there was no need to rebalance the engine as a whole.
THE FIX: CAM AND VALVETRAIN
Cam tech has evolved since the engine was first built 12 years ago. Hydraulic-roller cams are usually today’s preferred choice on the street. Brandes replaced Lane’s mechanical roller cam with a Howards hydraulicroller that, compared with the original, has similar mid-240s 0.050-inch tappet duration but significantly higher lift, particularly when the solid’s valve lash is subtracted from the theoretical lift numbers. The cam is ground with a conservative 112-degree lobe-separation angle (LSA). Brandes says, “The lobes are aggressive enough, and 112 is better for low-speed performance.” The grind was delivered as a cam-and-lifter kit that adds Howards retrofit-style link-bar hydraulic roller lifters. Brandes added PAC Hot Rod Series dual (with damper), 1.540inch od valvesprings to match the new cam. They fit Lane’s existing used retainers, which were OK for reuse.
With serious high-perf valvetrain parts, you must validate both piston-to-valve clearance as well as valvetrain geometry (the rocker arms’ roller-tip contact point on the valve-stem tip during the cam cycle). With the right pistons installed in the right holes, piston-to-valve clearance was fine. But the geometry itself can be affected by a cam change, block and head surfacing, differentlength valves or valve seat heights, different lifter heights or cup depths, and/or head gasket thickness variations. Valve length wasn’t a factor here because the lengths of the two replacement stainless Competition Products valves listed for a 429/460 Ford were the same as those they replaced. Valveseat height consistency is critical on a shaft-
mount engine, so Brandes freshened the valve job on all 16 seats, not just the two affected by the carnage.
There are several theories on proper geometry, basically boiling down to whether you want max performance or better durability. For ultimate performance on periodically torn-down race motors, Hughes sets up the geometry to obtain full cam lift. Provided it doesn’t actually roll off the tip edge, the amount the roller tip is off-center as it wanders back and forth across the valve-stem tip as the cam cycles is less important than max lift. For max longevity on primarily street-driven engines, Brandes likes to see
“This was a classic BFO: a blinding flash of the obvious. If the same parts keep breaking, you need to go deeper and find the cause.”
— Norm Brandes
the push point on the valve stem as centered as possible during the opening/closing cycle, even though this may not generate max lift on some combos. “It offers a straight push, centering the force. It’s easier on the valve; the guides last longer,” he says.
On shaft-mount rocker systems, both the rocker shaft height, rocker position on the shaft, and the pushrod length affect geometry. With Brandes’ method, at rest (valve closed, pushrod not lashed), the tip is centered over the valve-stem tip both longitudinally (edge-on) and laterally (side-on). Shim the shaft spacers and shaft pedestals as needed to get there. Then, using an adjustable checking pushrod and light checking springs, set the preliminary valve lash to zero, and adjust pushrod length to achieve minimum motion off-center through the cam cycle.
Lane’s old pushrods were about ½ inch too long, so Brandes got some made-toorder pushrods from specialty pushrod maker Trend Perfor- mance. Its entry-level ⅜-inch hollow pushrod has 0.080-inch wall-thickness (compared to 0.049 for the previous ones), and is made from 4130 chrome-moly steel with a proprietary casehardened heat-treat process. “They’re much stouter than the old ones,” Brandes says. The required pushrod length using the “over-ball” measurement method came out to 7.816 inches (yes, they’re that accurate).
After installing properly oriented pistons, the valvetrain was finally stable and reliable. The engine makes even more power than before, and at a more usable rpm, too!
Don’t mix Miller time with engine assembly time. Before installing the heads, compare the piston’s valve-notch orientation to the corresponding combustion chamber valve order. Seemingly random parts failures may not really be random at all. Careful record keeping would have shown the same part failed in the same installed position, providing a clue something may be wrong inside the particular cylinder and chamber. A piston-to-valve clearance check could have confirmed the issue before catastrophic failure.
01–02] When Lane’s wife, Janice, broke a rocker ( 01) while idling in hometown Burlington, Wisconsin, Lane knew he had to get the pesky problem solved. Westech Automotive’s Norm Brandes initially chalked it up to age and fatigue, replacing the entire shaft-mount valvetrain with new, stronger Hughes Engines parts ( 02). Designed specifically to solve Chrysler rocker arm issues, the CNC rockers have revised oiling that provides positive oil flow to the pushrod cup at any angle, eliminating the need for a rollerized shaft.02
[ Under the Plum Crazy–painted Road Runner’s air-grabber scoop resides a 496ci big-block Chrysler Wedge, run hard by the previous owner.
[ Ray Lane has owned this 1969 Road Runner clone since 2012. Before he got it, the car had acquired a reputation for breaking rocker arms.
[ After upgrading the shaft-rocker system, the next weak link failed: bent pushrods cascading into lifter, cam, valve, and piston damage.
03–05] Hughes’ rockers usually clear 1.625-inch-od springs, but Lane was running 0.050-inch positive-offset valve locks to get the right installed height with the springs needed to control his existing solid roller cam, leaving little clearance between the retainer top edge and valve-stem tip ( 03, arrows). Brandes had to deepen the relief on the new rocker bodies’ undersides. “With the valves closed, I used a piece of 0.030-inch-thick nylon fishing line to floss underneath the rocker. The check gauge must be flexible to follow the underside radius ( 04). At the closest approach point, I had to deepen the as-received radius by 0.075 inch in the mill ( 05). You could do this at home with a die-grinder, or even on a drill-press with a fly cutter.”
06–08] Several hundred miles later, the engine became noisy and developed a miss. Back at Westech, Brandes checked out the problem: “The Hughes rockers were fine, but we found massive carnage in the valley after removing the heads. Two pushrods bent and dropped down into the valley, where they bounced around and ended up behind the lifter link bars, snapping them and shearing the tops off two lifters ( 06). Two lifters actually turned sideways on the lobe ( inset).” Goodbye, cam lobes ( 07). Debris also scratched a cylinder wall ( 08)
09–11] Big-block Mopars have siamesed center exhaust ports; the exhaust valves for the center cylinders pairs 3 and 5 and 4 and 6 are adjacent to each other ( 09). Icon IC826 piston sets include two separate piston top configurations, each with a different valve notch order and size. On this motor, the Nos. 3 and 5 pistons were switched, causing the larger intake valve to hit the pistons above the smaller exhaust valve notches ( 10, arrows). Compare to the correct center piston orientations on the new, freshly installed, Icons ( 11).
13] With the new cam, Brandes installed matching PAC springs spec’d for hydraulic roller-cam big-blocks. Shorter than Lane’s originals, the 431-lb/in rate springs offers adequate retainerto-rocker body clearance with standard-height valve keys. These springs would have eliminated the need to clearance the rocker bodies. Dig the cool Goodson multiangle spring compressor.
12] Lane’s old timing chain was slacking off, so it was replaced by a premium Cloyes billet steel True Roller timing set with a nine-keyway crank sprocket and three-bolt cam sprocket. Brandes installed the new Howards hydraulic roller cam “straight-up” (on the “0” marks), as the cam already had 4 degrees advance ground-in (108-degree centerline on a 112-degree LSA).
14–16] Slide the rockers back and forth slightly on the shaft until the roller is centered on the valvestem tip as viewed edge-on from the cam valley. Once centered, measure the gap(s) between the rockers and spacers or pedestal retaining block ( 14). Add shaft shims to take up the gaps ( 15, arrows), or shave the spacer if a rocker can’t be moved far enough to center it. To laterally center the roller tip as viewed from the side, adjust the rocker shaft vertical height. Shim the pedestal ( 16, A) to move the rocker toward the intake side of the valve tip ( B); subtract shims to move it toward the exhaust side. If all shims have been removed and the contact point is still biased toward the intake side, mill the pedestal.
18] One way to accurately measure Chryslertype cup-end pushrod length is the “overball” method. After adjusting a cup-tipped checking pushrod’s length so it yields proper geometry, place a 5⁄16- inch ball in the cup and measure the length from the top of the ball to the pushrod’s other end. Be sure to let your pushrod maker (Trend, in this case) know how you measured. This measurement method compensates for different wall thicknesses and cup radii.
17] On street Mopars, Brandes sets valvetrain geometry to keep the rocker-to-valve contact travel point within the center third of the valve-stem tip throughout the opening and closing cycle. If the pattern’s biased toward the exhaust side, get a shorter pushrod; if toward the intake, a longer one.
19] Lane’s Chrysler big-block-powered 1969 Road Runner had previously run 11.30-second, 121-mph quarters on 93-octane unleaded, shifted by a 727 TorqueFlite that transfers the torque back to a 3.23:1-geared 8¾-inch Chrysler rearend with a Sure Grip limited-slip diff.