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.
Gene removed the lifter blocks, which aren't lifter blocks anymore. They are lifter covers that hold a hardened guide pin in place (the pin prevents the lifter from spinning) and seal the area with gaskets and O-rings. Throughout this process, we used a variety of JIMS tools to remove and replace components without risking damage. He removed the cam cover bolts and the cam case cover. It's not necessary to remove any ignition sensor from the cover.
We used a JIMS tool to hold the cam chain tensioners locked away from the chains after the cam cover was removed. Another JIMS tool held the gears in alignment so we could remove the gear bolts from the cam and pinion shaft.We popped the gears off then the chain tensioners were removed.
Then we moved onto removing the cam set and guide plate all as one piece. The S&S booklet documents specific fastener removal order for the oil pump and cam support plate. The cam system slipped right out of the engine case. In some cases, a press will be necessary to remove the cams and cam bearings from the support plate with a JIMS tool. In this case, the cams and stock bearings slipped right out of the support or alignment plate.
Another S&S Note: It's not necessary to remove the oil pump from the engine to complete this installation unless grinding in the gear case must be performed for clearancing. If grinding takes place, all gear case components must be removed and all holes taped off with duct tape to avoid contamination.
There's another JIMS tool to support the plate and install the new S&S bearings. Gene used a 1 1/16th socket as a guide to tap the new bearings in place after smearing them with Redline assembly lube. A few light taps and they slipped into place.
S&S supplied a new outer bearing retaining plate and it only slips on one way. S&S recommends checking the clearance between the bearing retainer and the woodruff keys securing inner gears to the cams. Remove material from the retainer as needed to provide .030-inch clearance between keys and retainer. Gene installed the bearing retainer plate and used blue Loctite and tightened the screws to 20-30 inch-pounds torque.
Gene grabbed the new S&S cam set and washed any anti-corrosion packing residue from the surfaces. Then he slipped the correct cam in the correct hole. The longer cam with the keyway is the rear cam. The two cams have alignment notches to indicate how they should be positioned. He used a press to install the cams in the cam plate, pressing the tall cam first until it was even with its mate, then pressed both into place. He double-checked to verify that the cams were aligned properly. Then he coated the crap out of all the new components with Redline lube.
He inspected the brass pinion shaft bushing for severe wear and performed a quick test fit to insure that no cam lobes would hit the case casting under the lifters. This wasn't a high performance set of cams, so there wasn't a problem, but it was good to inspect.
Again he used a series of JIMS expansion tools to remove the case cam bearings. The case cam bearings are the ones known to go to shit at between 10,000-25,000 miles especially under performance loads. The stock bearings are smaller, shorter and fewer in the race than the S&S performance roller sets.
Again a JIMS tools was used to carefully tap the new bearing into the cam gear case. Gene drove the new bearings into the case material until they mated with the inside case lip. While the case was still open, he inspected the oil pump for scoring. He also checked the back of the cam plate where the oil pump rides.
Gene also cleaned the lifter block gasket surfaces while the case was open. Any material that inadvertently fell into the case could be easily removed.
He installed the cam set and bolts loose and spun the cams to insure there was no binding or problems. He tightened the oil pump Allen fasteners, first alternating sequence, one through four to 95-inch pounds. He performed this task while making sure there was a gap beneath the pick-up opening in the bottom of the pump. If there was no gap, the cam case would fill with oil. He used a large flat-bladed screwdriver as a guide to insure the gap didn't disappear during the tightening process.
Then Gene tightened the cam plate to factory torque specs and installed the key and rear drive gear timed with the slots on the components. There's no way to go wrong unless you're blind. He almost forgot the front cylinder cam clip ring that prevents the cam from backing out.
“I never had one come loose,” Gene commented.
Gene installed the big cam gear bolt with Loctite and torqued it to 35 foot-pounds. The smaller gear, with washer and Loctite, was torqued to 25 foot-pounds. S&S supplied new fasteners with the gears, but he used the stock machine washers (S&S said you don't need 'em). Next, he replaced the hydraulic lifters.
“I always need to think about pushrod order and rotate the engine so the rear valves were down as far as possible,” Gene said. The new adjustable S&S pushrods were just two lengths. The two long ones were used in the exhaust sides.
S&S supplied all new covers minus the center spring retainers. Gene worked with the lifter blocks and pushrods to determine whether he could install the pushrods without removing the rocker boxes. A larger lift cam could pose a problem; these units were very close to being too long. Gene had to feed the intake pushrod, the lifter block gasket, and the pushrod covers into place in one dainty motion. It was a trick to hold and guide all the elements, but it worked.
I also learned the code of pushrod adjusting.
“You lower them all the way,” Gene explained. “Then you take all the slack out, and screw them down four turns. The hydraulic lifter doesn't move. You've opened the valve four turns. That's why you can't turn the engine over for ten minutes. If you did the valve could smack the piston. So you need to wait ten minutes for the lifter to settle, and then adjust the front cylinder.”
After all was said and done, the pushrods should spin when the engine is turned over and the valves cams lobes are down.
Again Gene checked the cam cover for clearance, since the S&S gear is larger than stock, but we still didn't face any clearance problems. He tightened the pushrod jam nuts on the rear cylinder, checked for spin, then moved onto the front cylinder pushrod adjustment. He waited another ten minutes, checked for pushrod spin, turned the engine over once for a final inspection then replaced the cam cover.
Gene added three quarts of Redline 20-50 synthetic oil and replaced my Screamin' Eagle exhaust system.
“It should hold four with a new filter,” Gene said.
Then I went for a ride.
This piece was final edited by Bruce Snyder who owns an '03 H-D. He made the following comment about his experience with cam drives:
Enjoy the ride. My local indy installed Andrews 26Gs in my '03 FXST a year ago (a tad milder than your S&S set) and I love 'em.
