Plain bearings are the simplest bearing type. In universal joints, the cross pins can run either directly within the joint yoke ear holes or in a bushing fitted inside the ear hole. Depending on the application, the areas of the yoke that take the highest load can be heat treated, or the contact surfaces hardened and ground/reamed to improve the running characteristics, reducing the friction between pin, block and yoke.

In researching timing sets, eccentrics, thrust plates, and high-output mechanical fuel pumps, we came across some reports that Ford-factory (or equivalent replacement) eccentrics—whether one- or two-piece—can't reliably do the job on high-output engines with high-volume mechanical fuel pumps. Metal-on-metal contact between the eccentric and the pump's lever-arm causes horsepower-robbing friction plus accelerates pump-arm wear, a problem compounded by the stiffer lever-arm spring used in high-volume pumps. Under sustained high-rpm use, the lever may even go into bounce. The solution is HiPo Parts rollerized eccentric. PN HPEX-6287-CLV fits 351C, 351M, and 400M. It includes an ARP 12-point bolt. Ease pump installation by installing the pump arm on the low side of the eccentric (TDC, cylinders 2 or 6 on the compression stroke).

Brokencamshaftcauses

But pulling that Number 1 lifter, I saw a ground-off foot. The corresponding Number 1 intake lobe on the cam was worn nearly round," Sanchez exclaimed

Here's where unanticipated problems started to rear up: Cloyes offers a bulletproof 9-keyway billet-steel True Roller timing set, but it requires a steel thrust plate. "You can't put a steel sprocket on a stock Ford cast-iron thrust plate without excessively wearing the plate," Sanchez explains. Clevelands are a dying breed here, but they remain popular down under, where Australia's Aeroflow makes a steel plate. OK, problem solved

Universal joints usually consist of two yokes – also known as forks – and a central cross-shaped element. The actual construction of this cross – or spider – is not standardized and varies from design to design. It can be manufactured either as a single component or as an assemblage of several separate components, typically a block or cube and pins which are fixed in the block to form the cross.

Bad camshaftsound

But, It turns out that the front face of Cloyes' billet chain isn't machined for a two-piece cam eccentric. Both one-piece and two-piece mechanical fuel pump eccentrics are available for Windsor small-blocks, but neither works on a Cleveland that uses its own unique two-piece configuration. Short of custom-machining the upper sprocket for clearance, the obvious solution is an electric fuel pump. Hicks wanted to keep the Mustang as visually "stock" as possible, so we went with Comp's rendition of a roller chain that uses a billet-steel crank gear but a cast-iron cam gear. Being iron, Comp's upper is OK with a stock thrust plate.

The durability of a plain bearing universal joint depends on the transmitted torque and the rotational speed of the shaft to which the joint is connected. The joint’s angle of deflection also comes into play. The higher the angle, the rotational speed and the torque, the greater the load on the joint. An excessive torque usually causes the joint to break. An acceptable torque at excessive speeds causes lubrication failure, which in turn leads to increased friction, resulting in extreme heat generation and increased wear. In the worst case, the pins, block and yokes may break or fuse. In any event, the joint becomes unusable.

Along with the cam, Godbold sent us a complete upper valvetrain including: springs, retainers, valve seals, and high-tech Pro Magnum roller rocker arms.

New parts in hand, Sanchez started to mock-up the cam in the block, putting a guided lifter pair on the No. 1 intake and exhaust lobes, and then began installing the timing chain.

Bad camshaftsensorsymptoms

Dan Hick found this out first-hand after rebuilding the Ford 351C stroker engine in his 1973 Mustang convertible. Upon startup, the cam almost immediately went flat. It wouldn't idle properly and eventually didn't run at all. He took the car to Mark Sanchez, Ford Specialist and owner of Advanced Engineering West, who got to work diagnosing the problem.

Sanchez quickly found the distributor was 180 degrees out of phase. "After I straightened out the distributor," Sanchez says, "The engine would run, but very rough, like it was firing on only seven cylinders. It didn't sound all that bad for what, at the time, I thought was a pretty big cam, and the idle system on entry-level carbs can't always play happy with a raggedy cam. Maybe I could make things better with careful adjustments, so I looked at the spark plugs. The No. 1 plug was wet and smelled of fuel; it wasn't burning. The other plugs looked OK.

To be honest, we're kind of jaded on flat-tapped hydraulic cams, generally. Today's retail consumer "starburst" motor oils lack the critical ZDDP zinc compound necessary for keeping flat-tappet lifters alive with today's modern cam profiles. Comp Cams' Valvetrain Engineering Group Leader Billy Godbold affirms this, saying, "You can do everything right to reduce the number of flat-tappet cam failures, but you cannot bring that number to zero."

In addition to the tendency to generate friction heat, plain bearings are likely to experience increased wear from abrasion. Even when overheating is not an issue, the running surfaces of plain bearings tend to wear, causing play or backlash within the bearings. In some cases, for example in motion control applications where precise positioning is vital, play or backlash is not tolerable. Here, the joint must work at near-zero play or backlash, often for extended periods. The exceptionally low wear of the needle-bearing joint makes it the preferred choice even in low-speed, high precision applications.

The tradeoff between a constructed cross and a complete cross is the way of assembly. A constructed cross (pins & block) can be assembled inside the yokes which can sometimes require fixturing or tricky manual work but when assembled will be in place with tight tolerances if machined correctly. A finished cross can be placed easily inside the yokes but the large gaps require the installation (and securing) of plain bearings, also referred to as bushings.

Badcrankshaftsymptoms

We also needed to make sure any mechanical fuel pump could keep up with the engine's 450hp-plus projected power output, with ample overhead for the usual "mission creep." The problem is the big names don't make (at least not anymore) a truly high-volume Cleveland mechanical fuel pump. Clevelands used to be popular in carbureted oval-track racing back before the SVO hybrid blocks, and that's why niche specialists like RobbMc exist. It has an interesting line of unique problem-solvers, including the only currently available true high-output Cleveland mechanical fuel pumps (right). It supports up to 550 hp at 7 psi without a regulator. It features big NPT side inlet and bottom outlets, a small NPT bottom port for a vapor return or fuel pressure-gauge line, and a 180-degree-rotatable valve body. This is plenty for Hicks' engine, but an 1,100hp version is also available (that one does need a regulator). There's even a $100 upgrade kit for existing 550hp models, so there's no need to spring for a whole new 1,100hp pump if your power needs keep climbing.

High speeds are also problematic for joints fitted with plain bearings, even if the transmitted torque remains low. The need for frequent lubrication of the bearing surfaces can present a problem where an oil-bath or drip lubrication system are not possible, as insufficient lubrication can lead to bearing failure caused by excessive temperature after just a short time.

What does abad camshaftlook like

"The Number 1 cylinder wasn't firing. The plug wire checked OK. I pulled the valve cover and cranking the engine over with a bump-start switch, I saw the Number 1 intake valve was barely moving. Turning the lash adjuster nut made no difference. The pushrod wasn't bent, so the next thing was to look at the cam and lifters. Number 1 lifter was not slack in the bore, indicating to me there wasn't excessive lifter-bore wear."

Some sources attribute this to lower cruise rpm (and hence lower sustained oil pressure) from mild rear axle ratios and overdrive transmissions used to meet tightening mileage and emissions standards. Regardless of the cause, Godbold claims, "Over hundreds of thousands of cars, flat-tappet cam and lifter failures were costing GM, Ford, and Chrysler on the order of over $100 per car on warranty and repair claims."

Showing only minor normal wear, the main and rod bearings were fortunately reusable. The oil pump was another story, with scored internal gears. Sanchez replaced it with a Melling high-volume pump, transferring over the old screen after a thorough cleanup.

Camshaftreplacement cost

Constructed crosses, which are often referred to as pin and block crosses, have blocks and pins generally CNC-machined from bar stock. The assembled cross consists of three or more individual parts. The common arrangement is one block with two or three, sometimes four pins.         Depending on the design, the pins rotate in the block or the yokes.

Not that flat-tappet cam failures were unknown 40 years ago. Even back in the '80s, when lifters and oil were still "good," Godbold maintains, "U.S. automakers were seeing too many unexplained cam failures that cost them more to fix than the upgrade to a roller tappet would cost." And that's with mild OE smog-era cams.

Bye-bye Number 1 intake cam lobe. Lifter trouble is afoot when it's lost its crown. The Number 1 lifter (left) is ground down so far, it's breaking into the hydraulic mechanism's center cavity. For some expert analysis, Sanchez sent the cam, lifters, pushrods, springs, and retainers to Comp Cams for inspection. Everything checked out OK, with Comp reporting, "There was no apparent reason for the failure."

Every engine has a different tolerance stack up, so it's always good practice to dial-in the cam in a high-performance build. Comp's billet steel crank gear may have "only" three keyways, but that was enough to degree the cam within degree of the timing card's 0.050-inch tappet-lift intake/exhaust timing events by installing the bottom gear in the 4-degrees advanced position (4 degrees advanced at the crank equals 2 degrees advanced at the cam).

A subscription to Car and Driver at age 10 set the stage for what would be John's career path. A voracious reader of car magazines and lover of all things automotive, he set out to learn as much as he could about cars. An automotive technology program provided the foundation, while fumbling around with large American sedans provided real world experience. Finally, a Bachelor of Science degree in photojournalism provided the focus. John accepted a five-month photography internship at Motor Trend magazine in 2003. Upon completion, he remained with the publishing company, managing a photo studio for 18 months before becoming photo editor for HOT ROD and Car Craft magazine. After three years on the production side, John accepted an editorial position at Car Craft in December 2006 and eventually became editor of Car Craft in 2014 and retained that position until March 2018 when he moved to HOT ROD as Executive Editor. He was promoted to Editor-in-Chief of HOT ROD in April 2019.

The journal diameter is usually smaller than the diameter of the corresponding yoke ear hole to allow the cross to be fitted in the yoke without difficulty. To achieve good contact between the surface of the journals and yoke ears, bearing bushings or roller/needle bearings are fitted in the gaps between the journal and yoke ear hole.

A solution to reduce friction between the bearing faces is the use of needle bearings in place of the plain pins or bearing bushings. Although needle bearings reduce the joint’s transmittable torque, they ensure that the joint can operate for longer periods of time without continuous lubrication. In addition, the technical data and calculation methods for specific loads and speeds that exist for roller and needle bearings allow the bearings’ service life to be estimated. Because of the numerous influencing factors occurring, service life cannot be accurately calculated for plain bearing joints. As a general rule, roller or needle bearings should be used for frequent- or continuous-duty applications with shaft speeds of more than 1,000 revolutions per minute. Plain bearing joints can generally be operated at such speeds for short periods. Their ability to handle these for extended periods depends on the materials used, finishes/coatings, and the lubrication.

Worncamshaftlobesymptoms

So, what was the root cause? Some might say "oiling." But Sanchez points out the Cleveland's Number 1 intake lobe gets oiled first, so if there was a lack of lubrication, then everything downstream—including all the other cam lobes, as well as main and rod bearings—should have had even worse problems.

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Any time you have a cam failure, a bottom-end inspection is also in order because all the debris from the failed lifter and cam lobe must go somewhere. The gunk in Hicks' oil pan didn't look good, so Sanchez prepared for the worst.

Flat tappet cams can be damaged by using modern engine oils that lack zinc and associated anti-scuff additives. Zinc can damage catalytic converters, so it's slowly been eliminated in modern engine oil that conforms to the latest API standards. That's not much of a problem for most engines newer than the late '80s and early '90s, by which time the auto manufacturers had fully converted to some sort of roller cam follower. Big problems arise when using this oil in an engine with a flat tappet cam that was designed for oil with high levels of anti-wear compounds. It's very easy to flatten a cam, and the only fix is to replace it and the lifters.

In sum, durability, not performance, was the initial impetus for the OEs' switch to roller tappets. Later, as carmakers got a handle on emissions and mileage, they developed a new generation of detonation-resistant fast-burn heads that worked with higher compression ratios and new high-lift roller cam profiles that can't be duplicated using flat-tappet technology. Bottom line: Go with a hydraulic roller cam if you can afford it, both for performance as well as reliability.

Godbold gave us several cam options, including a racy-sounding Thumpr. "Power-wise, nothing should beat the Thumpr on top with a Cleveland's 1.70:1 stock rocker ratio," elaborates Godbold. "Its 107-degree LSA [lobe separation angle] is a little difficult with vacuum and idle characteristics than what you would have with a wider, 109- to 113-degree LSA. For those who want a smoother-idling grind, our brand-new HLO profiles, originally developed for LS engines, would be perfect—but that would be a custom grind for a Cleveland. In an HLO, something about 227/239-degrees at 0.050 ground on about a 111-degree LSA would be very good." Owner Hicks had to have a racy idle, so Thumpr it was.

"Valvetrain assembly error"? Now you're getting warm. Before disassembling the cam and upper valvetrain, Sanchez noticed uneven valve stem tip wear across several valves. The worst misalignment was over the failed lobe, although we don't have proof beyond a reasonable doubt this was the proverbial smoking gun. Unfortunately, the only fix for a flattened cam is to replace it and the lifters with a new one, and it's at this point that most people switch to a roller cam.

Sanchez's plan was to correct the guideplate misalignment and replace the entire valvetrain with one compatible with a modern roller cam profile that matched the Cleveland heads' top-end flow characteristics. To do justice to the stroker engine's 42 more cubic inches over a standard 351, Hicks really needed to step-up from the original cam's 218/224-degrees duration at 0.050-inch tappet lift.

A subscription to Car and Driver at age 10 set the stage for what would be John's career path. A voracious reader of car magazines and lover of all things automotive, he set out to learn as much as he could about cars. An automotive technology program provided the foundation, while fumbling around with large American sedans provided real world experience. Finally, a Bachelor of Science degree in photojournalism provided the focus. John accepted a five-month photography internship at Motor Trend magazine in 2003. Upon completion, he remained with the publishing company, managing a photo studio for 18 months before becoming photo editor for HOT ROD and Car Craft magazine. After three years on the production side, John accepted an editorial position at Car Craft in December 2006 and eventually became editor of Car Craft in 2014 and retained that position until March 2018 when he moved to HOT ROD as Executive Editor. He was promoted to Editor-in-Chief of HOT ROD in April 2019.