 Techline-Sept.08-Part V: Cam specs and choices (cont.)
Part V continues:
Gearcase Issues
Let me start this with what the Wood Performance web site says: “It’s not how fast you go, but how quick you get there! Torque, torque, and more torque is the only way to put you there quicker and smoke the competition!” This design and manufacturing process has “produced the most advanced, aggressive camshaft profiles for H-D [Twin Cam] engines available anywhere! They yield very high torque and horsepower numbers, not matched by any other cams at this time.”
The Knight Prowler belt/gear-driven cam system uses either spur or helical cam gears on the inboard side of the cam support plate and a 5mm carbon-fiber belt drive and pulleys on the outboard side of the plate. No matter which system configuration you choose, refer to your Harley-Davidson manual for disassembly instructions. If you use the silent belt drive pulleys and Knight Prowler timing cover with the stock cams and inner timing chain, disassemble the engine to the cam support plate, leaving it intact and bolted to the engine. If you are going to replace the stock cams with a gear-drive setup, whether driven by S&S spur gears or Wood helical gears, you need to disassemble the cam support plate and oil pump. You should also remove the two inner INA cam bearings from the right crankcase using the proper Kent Moore tool (#H-D43644) or another tool of comparable quality. It is necessary, in my opinion, to measure pinion shaft runout with a dial indicator micrometer once you have everything out of the gearcase. H-D has been having problems with flywheel scissoring. As I understand it, the factory feels that up to 0.020" of runout on the sprocket shaft will not be felt by a rider on a rubber-mounted H-D. That thought alone makes me vibrate and shudder.
Bob Wood and I, as well as a host of other mechanics, are ecstatic with 0.000" runout on the end of the pinion shaft, happy with 0.001" and tolerate 0.002", but dislike anything above this. The consequence of this preference is the need to remove the flywheels to replace or retrue them. This is an onerous expense, so we reluctantly have to tolerate up to 0.004" of pinion shaft runout. If the crankcases are split, I will true the Twin Cam flywheels to my specifications of 0.001" or less at the shafts and rims, against Motor Company dictates. Of course, the crankpin will need to be TIG-tacked to the flywheels afterward to prevent future scissoring.
The advantage of a drive belt system is that it will tolerate higher runout figures than an inflexible outer drive-gear setup. However, this advantage does not help us with runout-induced vibration or stop the pinion bushing in the cam support plate, which the pinion shaft passes through, from being reamed out. These problems create a looser tolerance between shaft and bushing, which affects bottom end assembly bearing oil-feed pressure. Oil is pressure-fed from the oil pump, into the cam support plate, over to the pinion bushing, into the pinion shaft oil passage for delivery to the hollow crankpin, out three holes in the crankpin, and into and around the three sets of connecting rod roller bearings.
When doing any performance work, or even simple repairs, inside the gearcase section of the engine, it has become standard aftermarket industry practice to replace these INA inboard bearings with Torrington ones. These inboard 0.875" ID cam bearings for 1999-2006 H-Ds (#H-D 9198 or INA #SCE148), except the 2006 Dyna series, should be replaced by Torrington #B148 bearings. S&S bearing replacement kits (#33-5163) for 1999-2006 Big Twins, except the 2006 Dyna series, contain the cam cover gasket, two Torrington inner cam bearings, two outboard cam ball bearings, and a heavy-duty bearing retainer plate (#33-5212) to replace the not-so-strong H-D retainer for the cam support plate.
The larger inner diameter, 1" bearings for 2006 Dynas and all 2007 to present Twin Cams (#H-D 9215 or INA #SCE148) should be replaced by Torrington #B168 bearings. S&S bearing replacement kits (#33-5240) for the 2006 Dynas and all 2007 to present Twin Cams contain the cam cover gasket, two Torrington inner cam bearings, but no replacement outboard cam ball bearings since there are none. On these models, the outer ends of the cams run on parent material, so there’s no heavy-duty bearing retainer plate either. (The term parent material means the cams run on the actual cam support plate and not a bearing or bushing.) There are two flat, rectangular, hydraulic, block-off metal plates used after eliminating the hydraulic chain adjusters. Also, a flat washer is included for the gear drive assembly. For more information on this subject, see Volume I: The Twin Cam from my book series Donny’s Unauthorized Technical Guide to Harley-Davidson, 1936-2008.
Install any camshaft with a valve lobe lift over .510" into the inner cam bearing and rotate the cam to ensure there is a minimum of 0.030" of rotating clearance between the cam lobe and any obstructions on the right crankcase or in the gearcase. Each cam should be rotated by hand a full 360 degrees. Late 2006 and later Twin Cam cases have more clearance area cast into them at the foundry than 1999 to early-2006 Twin Cam engine cases. Ball bearings for both the front and rear outboard cam journals in 1999-2006 Twin Cams, except the 2006 Dynas (these incorporate the 2007 to present changes), are the appropriate choice for this application since the stresses imposed on a gear drive are somewhat different and reduced than those using timing chains, particularly the angled outboard chain. The stresses with timing chains require a roller bearing instead of a ball bearing for the rear cam’s outboard support. The 2006 Dynas and 2007 and later Big Twin models have parent-material outboard bearing surfaces that do not need to be replaced. It is very important to follow the Knight Prowler belt drive installation instructions for a comprehensive setup procedure. This is all new stuff that even experienced H-D mechanics will be unfamiliar with. It is not difficult, but we must walk first before we run.
Hydraulic Limiter Kits
I’ve been a big proponent of limiter kits in hydraulic lifters. This kit gives solid lifter performance with hydraulic lifter quiet when using high-lift cams in both Evos and Twin Cams. The limiter kit comprises four steel rings that are installed inside the stock hydraulic lifter. They limit the travel of the hydraulic tappet plunger in 1984-99 Evos, 1986 to present Sportsters, and, of course, 1999 to present Twin Cams. The S&S Cycle HL2T spacer rings are the most popular in use today. Kit #33-5338 fits 1984-85 H-D Evos, 2003 to present H-D Sportsters, S&S tappets for 1984 to present Big Twins/Twin Cams, S&S tappets for 2000 to present Sportsters, and 2003 to present H-D Twin Cams. Kit #33-5339 fits 1986-2002 H-D Big Twins and 1986-2002 H-D Sportsters.
I quote S&S Catalogue 1958-2008, High Performance Parts for American V-Twins: Since 1958, “When operated at high rpm, tappets have a difficult time following the cam lobes, and, therefore, may not deliver the intended cam timing. Hydraulic tappets have a tendency to partially collapse, making this situation much worse. HL2T spacers do not allow the tappets to collapse, so high-rpm performance is comparable to that of solid tappets. Another benefit of limiting tappet plunger movement is easier starting. When an engine is not running, the hydraulic tappets tend to bleed down. The effect of this is higher cranking compression when restarting the engine. Some high-compression, large-displacement engines may become very difficult, if not impossible, to start. With the HL2T spacer installed, the collapsing effect is minimized and both high-rpm performance and starting are improved. Under typical driving conditions, normal hydraulic function and the benefits of a hydraulic tappet (minimal noise and maintenance) are retained.” I still am a big fan of limiter kits when using Andrews, Crane, or S&S cams, to name a few. However, they are all longduration cams relative to their lifts.
The biggest cam I have installed other than Bobby Wood’s camshafts is the S&S 640G gear drive with .640" lift with 265-degree intake and 270-degree exhaust duration. These worked fine and actually performed better with the limiter kit. However, with a .650" lift and 248-degree duration on both the intake and exhaust of the Knight Prowler silent belt system, I tried to use an S&S limiter kit. The result was lots of noise, and no amount of tinkering would help. I turned to Bobby Wood for help.
Bobby informed me that the ramp rate design of the cam lobes and the amount of cylinder expansion growth due to operating heat expansion had more influence on noise levels than lift-to-duration ratios. Different manufacturers’ cylinders will grow at different rates, some more than others. This could be the situation with my particular build. He told me to take the limiters out and adjust the stock hydraulics down much farther than other manufacturers advise. The lifters will become a solid under duress with this procedure, which is what the limiters do. The total travel in an H-D hydraulic lifter, which, by the way, originates with the small block Chevy, is 0.190" to 0.200". Adjust the pushrods down 0.140" to 0.150". This will take the unit close to a solid lifter. Extreme riding will bring the pushrod down in contact with the bottom of the plunger travel, in effect creating a solid lifter of metal against metal with no oil-hydraulic buffer.
Story concludes in the next thread. Check back issue for pix and extra information. |
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