There's a code going around regarding Twin Cams. Lee Clemens pointed it out to me first, when he broke down on the way to Myrtle Beach on his FLH Twin Cam, with 25,000 miles on the clock. "The cam bearings disintegrated and took out the lower end," he said. The rumors are that the chain drive tension increases the load on the cam bearings and they begin to wear until they come apart between 10,000 miles, and as Lee Pointed out, 25,000 miles.

I discussed this with Gene Thomason of Gene's Speed Shop in Carson, California. We had an interesting chat about Evos and Twin Cams and which are the best. Gene and his dad, Gene Sr. worked for Bartels H-D in Marina Del Ray and for the Harley- Davidson fleet center for a decade. They know Twin Cams, every model and configuration. Gene Jr. is also an avid H-D top fuel drag racer, so he knows performance gremlins and how to deal with the stresses of performance enhancements.

"The Twin Cam exceeds the Evo, especially when it comes to performance," Gene pointed out. "Since it's mated to the transmission, alignment is enhanced and the cases are heavier and stouter design to handle the rigors of big-inch engines. The Twin Cam configuration allows the pushrods to be shorter and run at less of an angle to the rockers. The hefty cams don't ride on the cam cover, but a separate plate specifically designed to hold the cams more securely and in alignment with the case more effectively."

I like the Evo for its pure tradition, historic refinement and minimal components, but everything he pointed out was correct and a consideration for performance-minded riders. I asked Gene if H-D would ever install gear- driven cams and he pointed out that noise is a factor. Factories are allowed a particular level of noise to comply with federal standards. That level applies to the entire driveline from the exhaust to the tappets.

"Harleys like their exhaust rumble, so they try to keep the driveline quiet," Gene said.

You'll notice that Victory runs a noisy gear-driven primary, but the exhaust is quieter to level the regulatory playing field. I also reached our to our resident Bikernet.com Tech Expert, Pablo. Here's what he said:

”I hope you replaced the inner case INA (H-D) cam bearings with Torrington roller Bearings. Get them from Drag or CCI. The new 96-inch H-D engines also use INA inner case cam bearings, just a larger size.

”The Twin Cam INA bearings have the same issues like the EVOs did. They don't hold up with any performance work added to the engine. Cams, heads, stroker kits, and high-compression pistons enhance pressure on internal components. The Torrington bearings have more rollers, more bearing contact surface, and better support.

“Good choice on the S&S gear drive setup for sure. You might consider one those billet cam plates also. Check your Flywheel run-out also.”

--Pablo

I rode the 2003 Road King, with a measly 12,800 miles on the clock, to Gene's Speed Shop on Normandie in the Torrance, California Gasoline Alley (310) 618-1908. We pulled the bags and immediately performed a dyno run for a reference, although I wasn't switching the cams for additional performance. I had mid-range SE-203 cams in the bike with Screaming Eagle Heads, two-into- one Screamin' Eagle Exhaust and Terry Components closed-loop enhancement to my H-D EFI system. The bike ran terrific. The Dyno noted 68 HP at 6000 rpms and 84 pounds of torque at 3000.

"A stock 96-incher puts out 52 horses and 65 pounds of Torque," Gene said while straddling the King in his dyno room.

The 203 mid-range cam had .510 and .483 lift (intake and exhaust), and .234 and .239 duration. The S&S 570G cam set had .570 lift with .240/.255 duration. The S&S brochure point out the following benefits:

Reduced Maintenance: There are no chain guides or shoes to wear or replace and no debris from wearing guides or shoes to contaminate oil supply.

Consistent cam timing: Cam gears are keyed with a light press fit. Chain and tensioner induced variations are no longer a problem.

Load: Eliminating the chains and tensioners eliminates excessive side loading of cam bearings.

Critical sprocket alignment is unnecessary. Use of precision-machined spacers is eliminated.

Performance benefits: This system maintains accurate valve timing when using high performance valve springs with higher spring forces.

Performance fitment: Higher cam lifts can be used without decreasing cam base circle. Gear-driven rear cam rotates in opposite direction from chain-driven cam. Lobes on front and rear cams never point toward each other, allowing increased lobe height.

With the S&S Gear Drive Cam kit and their Pushrod set (which is required), we had all the components to perform the job, including gaskets. All S&S parts are guaranteed for a year to be free of manufacturing defects in materials and workmanship. The pushrod kit even comes with all the covers and O-rings, minus the centers with the springs and washers. We hoped the operation could take place without removing the rocker boxes. If we had to remove the boxes, we would need additional gaskets, not included in the kit.

The reason S&S supplies the covers include the proper length to afford us the ability to adjust the pushrods.

"Gear drives also prevent chain drive drag on a performance engine," Gene pointed out as he started to remove the air cleaner and pipes after the bike cooled.

We had to loosen the exhaust sensor, before removing the pipes. We removed the right footboard and Gene prepared to drop the oil drain plug.

"What's the deal?" he said. "There's still Bonneville salt on the drain plug."

I didn't have an answer and just kept my mouth shut and took notes. Gene pulled the sparkplugs, disconnected the battery and turned the engine over until the rear cylinder pushrods were down, after removing the pushrod cover clips. With bolt cutters he cut the non-adjustable pushrods and tossed them in the trash. Then he turned to the front cylinder. The S&S booklet recommended we jack up the bike securely, put it in 5th gear, and rotate the rear wheel until both lifters and pushrods for either cylinder are at their lowest point on the camshaft (TDC of the compression stroke). Both pushrods for that cylinder will not be under pressure from the valve springs and will rotate with light finger pressure.

Here's a note regarding the adjustable pushrod requirement: 510G camshafts may use stock style non-adjustable pushrods instead of adjustable pushrods. If installing non-adjustable pushrods, disassemble and assemble rocker box per Harley-Davidson instructions. All other S&S gear drive cams require installing adjustable pushrods. As a timesaving measure, the stock pushrods can be removed with bolt cutters. Be sure to heed cautions and warnings: use bolt cutters and not cutoff wheels to prevent debris from entering the engine. Cutting pushrods without releasing the spring pressure (lowest point on the cam) may result in bodily damage or a dead dog, if he's in the way.

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