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Subject: Wiping Cam Lobe Symptons???

Original Message
Name: Jeff
Date: July 15, 1998 at 05:17:13
Subject: Wiping Cam Lobe Symptons???
Comment:
Hi All,

I have been reading a lot of posts here lately about wiping cam lobes. What are the symptons of a cam lobe that has worn off? How does the engine run? Is there a way to tell without removing the cam?. I guess one obvious way to tell would be to visually watch the rocker arm and see if is no longer opening the valve. I did a cam change recently and the car runs great. However, is it possible to wipe a lobe, and the car still run good? It would seem to me if the valve was still opening slightly, the engine would not miss. Any thoughts on the subject?


Response Number 1
Name: darrell
Date: July 15, 1998 at 05:26:16
Subject: Wiping Cam Lobe Symptons???
Reply:
listen for a slight popping out the exhaust... on my first engine I overtightened the valve adjustment and it wore out a lob... it ran fine.. but you cannot tune out the popping...

Response Number 2
Name: Chris
Date: July 15, 1998 at 06:52:23
Subject: Wiping Cam Lobe Symptons???
Reply:
The symptoms include:

Lifter/rocker tapping
uneven idle (1 cylinder missing)
Popping out the exhaust

It's not a pleasant experience


Response Number 3
Name: Topp
Date: July 15, 1998 at 06:54:36
Subject: Wiping Cam Lobe Symptons???
Reply:
After going thru this myself, in addition to popping out the exaust, also look for popping thru the intake. Watching the rockers is not a good way to tell, cause a majorly worn cam should still rock the rocker.
When I finally pulled the cam, I had 6 worn lobes. None were rounded totally. All were on the passanger side.

Looking at the cam, I could see the wear on the lobes.

Another thing i remember when doing diags., was that when cold, the car wouldn't idle right. It'd fire up and then run for a few seconds and then stumble and die.

My .02


Response Number 4
Name: ED
Date: July 15, 1998 at 07:37:18
Subject: Wiping Cam Lobe Symptons???
Reply:
A post below complained of a top end miss. This could be a indication of cam lobe wear in that at rpm the valve or valves arenít open long or far enough to get a good supply of fuel/air mixture and the engine power fades and just doesnít perform.

Any one indication alone wont indicate a worn cam lobe, you will need several.

Pooping out the exhaust or up through the intake could also indicate a burnt valve, bent valve stem, worn valve guides, broken push rod, burnt plug wires, open plug wires, the list could go on but the idea is that several things have to happen at the same time and you need to check out everyone.

A compression test or cylinder leak down will check normal when a cam lobe is worn. These two tests wont help to diagnose cam wear. You will need to eliminate possible causes one by one.

You get the idea of what it takes to get down to it.

ED


Response Number 5
Name: DaveB
Date: July 15, 1998 at 08:33:34
Subject: Wiping Cam Lobe Symptons???
Reply:
An easy way to tell is to set up a dial indicator and monitor the total lift at the retainer while turning over by hand. [plugs out of course] All of the intakes ahould be the same and all of the exhausts should be the same. [Some cams have different intake and exhaust specs] This is a positive way to check for cam wear with no guessing.

Response Number 6
Name: Nick
Date: July 15, 1998 at 09:36:12
Subject: Wiping Cam Lobe Symptons???
Reply:
I would definitely agree with all of the above responses...I had a cam lobe go flat in a '65 Buick recently, and it exhibited a lot of lifter tapping, missing cylinder, etc. Also, we pulled a 350 out of an '80 Blazer a few years ago that showed no real symptoms of valvetrain problems, yet 2 lobes on the cam were flat. I also wouldn't be surprised to see popping through the intake or backfiring through the carb as someone mentioned earlier, as those same things happened to my '64 El Camino when it broke a rocker stud, which of course looks the same as a flat lobe to the valve!

--Nick


Response Number 7
Name: Gene McGill
Date: July 15, 1998 at 10:20:50
Subject: Wiping Cam Lobe Symptons???
Reply:
Mine started with popping at high rpm, but got lower as the wear got worse until it was finally doing it at idle (I had no idea what was causing it until it was doing it at idle and I could see the valve was not opening...long before this site was around). It was a big cam with a rough idle to begin with, so I really didn't notice any change in idle (initially). There was no rocker arm/lifter noise through out the whole disaster, and it lasted probably a year (10,000 miles maybe) from start to finish, staying away from high rpms during that time.

Response Number 8
Name: Bill
Date: July 15, 1998 at 20:18:19
Subject: Wiping Cam Lobe Symptons???
Reply:
All of the above are right on. I had a Chevy truck that had been serviced properly and a cam lobe went flat at 70,000 miles, the dealer mechanic said that either the metal in the cam was not tempered properly or bad batch as he had changed out several. Good luck!

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