Worn Cam Lobe:
 

When I used to be envolved in automobile high performance engines, one rule of thumb for cams was, if engine is to be used for a lot of street use, keep the valve lift below .600" or expect a short lived valve train. Based off of what I found here, I'm getting ready to pay the price of violating this rule on our highway cruiser. I have seen some posts that indicate others are seeing rapid wear on cams and lifters in Twin Cams, possibly others violiating this rule of thumb, what do you think?

Bike being an Ebay special a few years back, I decided to tear my TC'supper end down this winter to check things out and see exactly what I have. With cam cover off I decided to take a looked at cams with penlite the best I could, rear cam lobe looked suspicious. Pulled cams out, found one badly worn lobe and others were starting to show wear. The Cams are S&S 625Gs. I thinkmy violating this rule of thumb with their .625" lift bit me.

I would estimate that these cams have approx 20,000-25,000 mileson them. For longgevity, insteadI think I should pick a cam in the approx .550 lift range. Any comments?

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RE: Worn Cam Lobe:
 

S&S are very good products. Have you any idea of valve spring pressures??
I just put in a Woods 7H cam (0.575) with his springs fitted for his 400 Cam (0.650) if I want to go there later. The springs are supposed to be about as good as possible and his cams looks beautiful compared to HD stock. Also lifters are something to think about,were they S&S or stock ones?
I put in Fueling extra oil lifters, but they look exactly like stock ones. Maybe inside they are different.I think if I was going to the woods 400 cam, I would use Jims or other very good units.
Course S&S cams, lifters, pushrods, roller rockers, springs, valves,certaintlywould be a good package.
And last, lubrication. Who knows what before you got it. I like Amsoil or Mobil1 Syn. Filters also. Harley's filter is 5 micron. Needs lots of warmup with this I bet. Takes about 15 min to warm up going slow. Kinda like an airplane. Caint take off without the oil hot.

Just some things to think about. I've though about some of this for almost 50 years now doing one thing or another.

RE: Worn Cam Lobe:
 

Thanks for your input. It appears thatall valve traincomponents are S&S, including rocker arms. You bring up many good points about lubrication etc. I'm not sure what the valve spring pressure is but now would be a good time for me to find out.

However, I think this re-confirmed my idea that, if you want to curise 10s of thousands of miles reliably, keep your lift and corresponding spring pressures for lifts under .600". We sure found this out the expensive way with radical automotive engines and an air cooled engine's components usually see the dreadedmore extreme temperature variations. Being an Ebay special, I had no idea that the lift was .625, had I known this, I would have paid closer attention to the valve train. No wonder I had trouble getting it to idle under 1000 RPM.

RE: Worn Cam Lobe:
 

OK guys, you will here it first right here. Just got off the phone withone of the more seasoned Tech Consultants at Crane Cams discussing premature lifter/lobe failures, like I have. He stated that one of maincauses is usingSYNTHETIC OIL!. It can be too slippery causing the lifter's roller to slide, instead of turn,on the cam lobes eventually causing flat spots on the roller and chewing up lobes. I think this Tech is for real becauseour discussionswent back to the time when GM switched to synthetic oil in their cars and immediately started having these failures. This Tech worked with GM on the problem and the solution then was to grind cams with a rougher lobe surface for better traction on the rollers for synthetic oil useage. This rougher surface is not normally used on aftermarketcams due to the common useage of non synthetic oil. So there you have it.

Now I'm not sure this has caused my failure yet, even though I use Mobil I 15W50.I have to pull lifters and check for small flat spots on roller and if present, according to him, my oil probably caused it.

I will go along with him on this. Theonly reason I used synthetic was because of its higher oil temp lub capabilities. But after installing an oil temp guage, I find that I have the opposite problem, I have trouble getting the oil temps up to the desired 220 deg F. It takes more then 50 miles ofdriving to get good oil temps and many trips most bikes take are less then that.

I had more to say but wife just said someone is on their way over to visit and I am not presentable. Got to run.

RE: Worn Cam Lobe:
 

If it was only on one cam, It could also be hardness issue of that lobe, Maybe??

RE: Worn Cam Lobe:
 

Cam lobe wear is a problem in recent yrs due to new requirements in oils.The anti wear ingredients have lessened,zinc I believe.This was mainly due to oil burners even if slightly clogging cat converters.So thee oil industry has been experimenting with stuff like teflon.The old additives like EOS is no longer made or at least contain the same amount of zinc additive.ZDDP is another additive but not cheap.The auto industry has been dancing around correcting designs to lessen this wear occuring.The syn sliding statement is BS.

RE: Worn Cam Lobe:
 

I might buy the oil is the problem line if all the lobes looked the same. but just one? it might just be a bad lifter roller thats starting to seize or some other lifter problem. when a lifter wheel bearing went on my evo, it screeched then blew apart. the bearings in the roller trashed the motor.,,

RE: Worn Cam Lobe:
 

I have to agree about the oil not being the problem. Almost every engine todayespecially the best examples, uses SYN. and all pushrod engines, of all type, including my Cummings in the pickup have roller lifters. I am inclined to think hardness somewhere, lifter or cam lobe, caused this. Could happen.
The bigest porblems SYN had years ago was engines leaked because the chemicales shrunk the seals, especially the old engines seals and gaskets. That was 25 years ago.
Also the Mobil1 I use is the V-Twin version from WM. These different applications are made different. The additive package for Diesel oil is loaded up with more anti-whear that gas engines, for example. I expect the V-Twin version is closer to the diesel version than the gas oil.
Red Line Primary oil and Red Line Supershock for the transmission.

RE: Worn Cam Lobe:
 

There were other lobes on both cams that were starting to showabnormal wear, I just showed a picture of the worst one. After examining the lifters, I could not find anyflat spotting, so the rollers must have been turning freely. The lifter from the worst lobe showed some wear but not as bad as I would haveexpected compared to how badthe lobe looked. I still say, running.600+ lift on avalve is asking for short livedvalve train components for street use.

RE: Worn Cam Lobe:
 

Oil is not the problem here. From what I see the cam lobe that shows the most wear is the one that the pushrod is at the most extreme angle when running. That is usually the cam lobe that shows wear first due to the extra stress of the pushrod running at more of an angle. My cams showed the same lobe wear when I did my tensioners. Also the extra tension from the valve springs on high lift builds will add to the wear problem too.
If you look at your engine you'll see what I'm referring to. The pushrod on the front cyl. that angles to the rear is the culprit. It is in a position that adds more stress to the assembly for that valve. I have read that it causes that kind of wear.