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CVO Technical => Twin Cam => Topic started by: lilcoot on February 17, 2012, 02:46:24 AM
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This subject has been beaten to death, but I'll bring it up again. I'm getting ready to spring for new cams on my 2012 SG, and I've been talking with a local indy who supposedly knows his stuff.
My problem is this: He (the tuner) strongly recommends installing gear drive with the cam. I've been led to believe there's no reason to do this on the newer bikes with the improved chain/tensioner set up. Is there any reason to have gear drive installed? Or is this guy trying help, or is he just trying to make a few extra bucks?
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Not sure about the tensioner point, but I was told to stay away from gear drive cams due to the excessive crank run out that the 110's have. The more crank run out, the more wear on the cam gears. Chains are more forgiving to the loose tolerances.
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Not sure about the tensioner point, but I was told to stay away from gear drive cams due to the excessive crank run out that the 110's have. The more crank run out, the more wear on the cam gears. Chains are more forgiving to the loose tolerances.
not specific to the 110 on the runout...if you are set on the gear drive have the crank pinned and balanced. all builders have there own preference but they all also agree that no runout on a stock crank is impossible without extra $$$$...gear drives are also a bit noisier, but not like these motors arent noisy already
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Gear drives are a little more accurate in terms of cam timing than a chain drive, but the difference is much less with the latest system from Harley versus the sloppy system from '99-'06. Unless you plan to put the bike on the race track and thus need every tenth of a horsepower, it's not a valid consideration. But the argument does sell lots of parts.
The biggest factor on late model ('07 and later) bikes is the sloppy crank. And it's not good enough to just measure the current runout and if it's .002" or better (fat chance) think you can just throw in the gears and forget about it. These cranks are subject to shifting at any time, so unless you plan to pull the crank and have it trued, plugged, welded, etc., I wouldn't even consider gear drives. A good up-to-date Harley engine guy should know this and not try to sell gear drives without explaining all of this. I can't tell you the motives of your guy, but I've run into more than a couple who still push gear drives just because that's what the hot setup was ten years ago so they assume it still is. Plus they make a lot of money on them, of course. After all, they are in business to make money, right?
Jerry
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Go Chain!! :2vrolijk_21:
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OK the crank has been adequately explained
Consider also the thrust control of the cams as well. Many have experienced failures in this area.
Run stock chains and hydra tensioners. Reliable quiet forgiving
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Guys, thanks for confirming my suspicions. Being fairly new to the HD world of modifying can be confusing, especially when a so-called expert contradicts everything I've heard (no offense, Darth ;)). He also recommended Andrews 31H cams in 110s....
"OK the crank has been adequately explained
Consider also the thrust control of the cams as well. Many have experienced failures in this area.
Run stock chains and hydra tensioners. Reliable quiet forgiving"
Deweysheads, since you mentioned it ???, could you please give a brief explanation of what you mean by thrust control of the cams and how it is affected by chain drive vs gear driven cams?
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I've seen two builds with gear drive systems installed in the babbitt bearing cam plates, both had extreme wear in the babbitt bearing journals. Both of these builds had less than 1000 miles on them and I was shocked at the damage done in that short of time. One of the builds actually had to have the cam plate replaced. Gear drives where necessary in pre 07 bikes but I would NOT use them in the new cam plates.
The 31 cam is a bust for the 110'' motor....works fine in a 95''. It's been my experience that unless you raise the compression to 10.5:1 in the 110'' motor no cam will really work as well as the 255 you have now. Sure you will gain HP however with a cam change but the tq will fall a great deal where you ride all day long.
Doc
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I certainly wouldn't let a cheap faulty factory bottom end sway my choice of cams....but that's just me
How about a Timken conversion & trued /balanced /welded crank ?
:nixweiss:
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I certainly wouldn't let a cheap faulty factory bottom end sway my choice of cams....but that's just me
How about a Timken conversion & trued /balanced /welded crank ?
:nixweiss:
Only if you feel like taking the motor apart.....
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Only if you feel like taking the motor apart.....
The old "if it ain't broke" saying doesn't really apply, it came broken from the factory, may as well fix it right while you're fixing it.
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The old "if it ain't broke" saying doesn't really apply, it came broken from the factory, may as well fix it right while you're fixing it.
Wasn't the best from the factory, but I would ride it a while and if it breaks the MoCo will pay for it...then you can just add some more $$ and have the crank done at that time. But that's just my opinion....