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Wiped Cam Lobe

17K views 14 replies 10 participants last post by  SWHEATON 
#1 ·
What are the symptoms of a wiped cam lobe:

  • Intake lobe?
  • Exhaust lobe?
 
#2 ·
most people would say popping.....sometimes rough-running

What is your car doing Rich?
 
#4 ·
George, it's popping and getting progressively worse. Started out popping on deceleration only but now pops all the time. My suspicion has been an exhaust lobe but it's only a guess. That's why I asked intake versus exhaust lobe.

Now that I've got your attention, if it comes down to replacing the cam, do you have any recommendations. It's a completely stock L34/TH400/3.31 and I would consider something a little better than the original bump stick.
 
#13 ·
George, it's popping and getting progressively worse. Started out popping on deceleration only but now pops all the time. My suspicion has been an exhaust lobe but it's only a guess. That's why I asked intake versus exhaust lobe.

Now that I've got your attention, if it comes down to replacing the cam, do you have any recommendations. It's a completely stock L34/TH400/3.31 and I would consider something a little better than the original bump stick.
The 402 in the '70 is a '66 L34 short block, 063 heads, GM aluminum intake, 3310 Holley, and Isky Z-45 solid lifter cam. It runs real nice, and does well with the 3.31 gears and M22. It doesn't like real low parking lot RPM's, but other than that it drives off nice and definitely has some umph to it.
 
#5 ·
Rich, How long has the engine been together? What kind of oil do you use? Just curious. I had always hoped that if an engine made past the first 1500-2000 miles you had it licked.
 
#6 ·
Troy,

I don't know the history of the engine. I've had the car for 4-1/4 years and it has always run well up to now.

As for oil, I have been using Delo 400 with 1-1/2 oz. of Lucas Engine Break-in Oil Additive for additional protection. I guess it didn't work!

Rich
 
#8 ·
Pull the valve covers just to make certain. Let it idle and watch the rockers move. The one that barely moves or stays put is your culprit.
 
#11 ·
My dad said when he was driving our car in 1995 and the cam lobe went out, the engine was running VERY rough and misfiring like crazy. He also mentioned that the idle was very erratic and would way up and way down. He pulled over and had a wrecker come out and tow it home.

I myself have had a rocker arm nut back out and had the rocker fall off the pivot and it was causing a higher than normal idle yet running very rough. Glad it something so easy. I pulled the right side valve cover off and immediately saw the rocker arm sideways haha.

Good luck!
 
#12 ·
Yeah, mine didn't run right, and sounded like a rocker was out of adjustment.

I pulled a valve cover and used a remote starter to watch the valves so I didn't have to have it running and make the mess. You could obviously see which one wasn't moving anymore.
 
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