What is a wiped lobe??
Safety Car
Joined: Aug 2000
Posts: 3,909
Likes: 26
From: Clymer PA
Re: What is a wiped lobe?? (Aaron-74)
A wiped lobe occurs when a cam lobe goes "flat." Symptoms are backfiring when the timing is correctly adjusted....runs like crap pretty much anything past idle.
Race Director
Joined: Dec 1999
Posts: 16,945
Likes: 9
Re: What is a wiped lobe?? (Aaron-74)
When the valve is adjusted too tight (or the spring pressure is too high or different on different springs due to incorrect installed height, the geometry isn't correct, and so on) and you go through the hardened outer layer the wear goes very rapidly. To diagnose it in an early stadium you must use a dial indicator to measure lift on all valves and look if they're all the same.
Marck
[Modified by Twinnie, 6:14 AM 9/20/2002]
Marck
[Modified by Twinnie, 6:14 AM 9/20/2002]
Burning Brakes
Joined: Mar 2001
Posts: 1,211
Likes: 5
From: Nashville TN
Re: What is a wiped lobe?? (Twinnie)
The horizontal tie bar broke, which allowed the lifter to turn and act like a cutting bit on a lathe. The tie bar parts took a ride in the engine. Below is what I saw when I pulled the intake off.
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Burning Brakes
Joined: Mar 2001
Posts: 1,211
Likes: 5
From: Nashville TN
Re: What is a wiped lobe?? (Twinnie)
No other parts. But I was not sure of the remaining life left in the motor. I invested $100 in a solid lifter LT-1 cam and stuffed it in. After about 4 oil changes everything is running well. Which I would attribute to a. the magnetic drain plug in the oil pan and the fact that all the little pieces found their way to the oil pan without running into to many parts.
Comp cams warranteed the roller cam. I ended up sending it back to them for a credit.
Comp cams warranteed the roller cam. I ended up sending it back to them for a credit.
Race Director
Joined: Dec 1999
Posts: 16,945
Likes: 9
Re: What is a wiped lobe?? (dman535)
You didn't pull the engine apart? Oh man, that's brave. If itwere me I couldn't live with the fact that somewhere in the oil there may be a chunk of metal waiting to ruin the entire engine.
Some screening in the valley could have safed some trouble too :)
Marck
Some screening in the valley could have safed some trouble too :)
Marck
Drifting
Joined: Jul 2000
Posts: 1,266
Likes: 0
From: Allen, TX, USA
Re: What is a wiped lobe?? (dman535)
> warranteed the cam...
I'm surprised that they would do that given that cams
wear with improper setup. I guess it's the cost of doing
business.
Lucky for us.
Burning Brakes
Joined: Mar 2001
Posts: 1,211
Likes: 5
From: Nashville TN
Re: What is a wiped lobe?? (adam)
There is nothing improper about the setup of this valve train though. A horizontal tie bar rivet let loose which caused the eventual failure of the camshaft. This is after 8000 miles ! The whole reason I went a roller was increased reliability.When I bought the cam and lifter set I had to warranty a lifter set because one of the lifter wheels was seized. Not impressed with QA at Comp Cams.
I figured I would gamble with a new cam. I choose a solid lifter so that and small particles would not get caught in the hydraulic mettering orfices. So far so good. Besides if this motor takes a dump I have a 400 sitting in the garage. :)
I figured I would gamble with a new cam. I choose a solid lifter so that and small particles would not get caught in the hydraulic mettering orfices. So far so good. Besides if this motor takes a dump I have a 400 sitting in the garage. :)
