# Could it be bad lobes on cam ?



## wlbuckles (Apr 3, 2010)

Have a 65 gto 389 with top end Ticking ot Tapping sound. Adjusted the lifters according to specs. Still have noise. Noticed 2 push rods on right bank not rotating at idle. Are we looking at possible flat lobes on cam or bad lifters or both ? Could use some sound advice. Thanks. :confused :confused


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## Jerry64 (Apr 20, 2010)

Are the rocker arms moving up and down like the rest?If not odds are it is the cam.Push down on the end of the rocker while running if they are moving like the rest and see if the noise stops..May have a pulled rocker stud.......JB.


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## Eric Animal (Oct 28, 2007)

Also could be a bent push rod.....check the easy stuff before you pull the cam and lifters!


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## 646904GTO (Feb 10, 2008)

If you see more stud thread sticking out above any rocker nut then you might have a flat cam...Those studs are screw in so pulling one is not likely. You may just need new lifters if they look even. The pushrods don't always rotate but they should. I just did a 455 with similar issues, even though the lifters had few hours on them I changed them and then after I was done with the 'adjusting' sequence they ticked, pulled the covers and gave all of them 1/4 turn more, ticking gone. Good luck


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## Jerry64 (Apr 20, 2010)

If the heads are stock 65 ,They should have pressed in studs...66 GTO's stock heads are pressed in also BTDT.....Check to see if the 2 studs are higher than the others for a start...JB


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## Eric Animal (Oct 28, 2007)

:agree All good advice!


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## wlbuckles (Apr 3, 2010)

Checked all rocker arms at idle and all are pumping strong. Pulled all push rods and all are clean and straight. Same thread lengths at top of studs. Sounds like it's time for a good set of lifters. What do ya think guys ??? :confused


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## geeteeohguy (Feb 2, 2008)

I think it's time to get the dial indicator out and measure your cam lift. Putting new lifters on a worn cam won't fix anything. If your lifters are worn, there's a good chance the cam is, too. JMO


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## Jerry64 (Apr 20, 2010)

Flat cam would be obvious when running.........JB.


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## jetstang (Nov 5, 2008)

I went into my 400 for 2 cylinders ticking to replace lifters. Lifters and cam were shot. Lobes were not flat, just flat on top, so engine ran on all 8 without a miss, just down on power. I'd plan for a new cam and lifters. I swapped motors, as the old motor was a grease pit and had 100K on it.
I adjusted my rockers with it running, when the tick went away it floated the valve. The motor really ran good when I pulled it.


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## Rukee (Feb 8, 2007)

jetstang said:


> I went into my 400 for 2 cylinders ticking to replace lifters. Lifters and cam were shot. Lobes were not flat, just flat on top, so engine ran on all 8 without a miss, just down on power. I'd plan for a new cam and lifters. I swapped motors, as the old motor was a grease pit and had 100K on it.
> *I adjusted my rockers with it running, when the tick went away it floated the valve.* The motor really ran good when I pulled it.


That sounds like a collapsed lifter.


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## jetstang (Nov 5, 2008)

Rukee said:


> That sounds like a collapsed lifter.


Exactly, so I pulled the valley to install new lifters and found a flat lobe camshaft, and ovalled out lifter bottoms. Ovalled bottoms stopped the pushrod from spinning as the lifter didn't spin anymore due to the worn cam/lifter interface.
My machinist buddy says to run break in lube with every oil change to protect the cam from damage as oil doesn't have ZDDP in it anymore. Old news to most of us, but a good time to put it out there for someone with a ticking cam.


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## Rukee (Feb 8, 2007)

Valvoline Racing 20W-50 has the ZDDP, it's the only thing I run in the GTO.


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## wlbuckles (Apr 3, 2010)

Jerry64, you said flat cam would be obvious when running. would you please explain further ? Thanks.


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## Rukee (Feb 8, 2007)

wlbuckles said:


> Jerry64, you said flat cam would be obvious when running. would you please explain further ? Thanks.


Look at the rocker arms while it's running, a flat cam lope will hardly move the rocker arm if at all. It should be somewhat obvious. It's also common if it's an exhaust lobe that's gone from the cam it'll sometimes backfire or pop through the carb.
Another trick someone showed me for a valve problem, use a dollar bill and hold it up flat and loose to the exhaust pipe while idling, Sometimes with a valve issue it will randomly suck the bill up the pipe which will never happen with a healthy engine.


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## jetstang (Nov 5, 2008)

His motor sounds like mine, it just has a tick he can't get rid of. He didn't say dead miss or anything. My cam lobes were intact, the just weren't pointy anymore on 2 cylinders.
If you can't adjust the noise out, only way to find out what's going on is to pull the intake and valley pan and take a look. Good luck! It may be the lifters just failed, pull the offensive lifters out and look at the bottom and make sure they are still flat, if ovalled, replace them.
Or post a video of it running and let us hear the engine.


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## Jerry64 (Apr 20, 2010)

I'm back.Been down on the Gulf coast for a week........Warren I sent you an answer to your PM last night.....Check the lift while running and if some of the rockers don't have the same lift the lobes may be worn...........JB.


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