Valve Tapping?

[Dano]

Greetings all,
I'm not a gearhead so please bare with me. I have a 83 CJ7 w/ original GM 151 engine (new Weber carb). After driving about 15-20 minutes I start to hear what sounds like a valve tapping. A ticking. I pulled over to check the oil, which was fine, got back in the jeep and the tapping stopped for the rest of the day. The tapping seems to be intermitted. The jeep runs great and strong. I figured I'll check out the simple stuff first like rocker arms and push rods first.
Just wanted a 2nd and 3rd opinions before I start taking this puppy apart.
Also, I seem to be getting excessive blow back at the vent on top of the head cover.
Thanks to all who respond.
Danny

 

[jeffgtoman]

Several things that can cause this would be.
1. Low oil pressure. Check it with a known good manual gauge.
2. Dirty oil. Has it been changed within the last 6 months or 5000 miles.
3. Diluted oil. Check for gas in the oil. A carb can leak into the oil pan, especially when sitting overnight.
4. Worn lifters from using the wrong oil. The newest oil on the market does not contain the right anti-scuff ingredients needed for an older engine with standard lifters.

 

[BusaDave9]

Ticking valves. Usually this is a lubrication problem with the valve system. That's what jeffgtoman was pointing toward. When the cam tries to close the valve but the valve sticks for a fraction of a second and makes a ticking noise when the spring pulls the valve closed later than the cam intends.
jeffgtoman had some excellent suggestions all pointing to lubrication. If none of that pans out you may need a valve job. A valve job may mean you might as well rebuild the engine. Of course your engine isn't dead now. Just preparing you for the worst case.
Another possibility is detonation. We are not there to hear the noise but to make sure it's not detonation try using premium gas for a while. Don't get me wrong: this is NOT the fix. It is only to troubleshoot to see if you have a detonation problem. A CJ shouldn't need premium. If it is detonation we may look at things such as timing.

 

[CJim7]

Another thing to look at is rocker components. I've seen the cups worn out so bad on Jeep inline engines that the pushrod was pushing through it. Also if the pivots are worn, the rocker will make noise against it.

A quick inspection with the valve cover off will verify or eliminate that part of the valve train as being the problem... I've solved a noisy valvetrain replacing rockers, pivots, and pushrods alone, as long as that's the problem.

WARNING:
If you figure out you have a bad lifter(s), do not replace the lifters alone. The cam and lifters break in together and replacing one or the other will cause cam failure usually in the form of a worn and rounded lobe. This also puts all sorts of hardened metal into the engine causing further damage.

 

[fzsk4p]

Another thing to look at is rocker components. I've seen the cups worn out so bad on Jeep inline engines that the pushrod was pushing through it. Also if the pivots are worn, the rocker will make noise against it.

A quick inspection with the valve cover off will verify or eliminate that part of the valve train as being the problem... I've solved a noisy valvetrain replacing rockers, pivots, and pushrods alone, as long as that's the problem.

WARNING:
If you figure out you have a bad lifter(s), do not replace the lifters alone. The cam and lifters break in together and replacing one or the other will cause cam failure usually in the form of a worn and rounded lobe. This also puts all sorts of hardened metal into the engine causing further damage.

All the answers thus far are decent but Dano`s is an intermittent issue.

Worn lifters, rounded cams etc would cause a continuous noise. Not one that comes and goes.

Dave was on the money IMHO of detonation or pre-ignition. Cold weather does make an engine run lean. As do the additives the refineries add to the fuel to make it more volatile in cold weather.

Dano, like Dave said. Run a tank of 89 or better through it. See if you can recreate the same circumstance that caused the rattle to begin with.

Drive and don`t worry about it.

 

[CJim7]

All the answers thus far are decent but Dano`s is an intermittent issue.

Worn lifters, rounded cams etc would cause a continuous noise. Not one that comes and goes.

Dave was on the money IMHO of detonation or pre-ignition. Cold weather does make an engine run lean. As do the additives the refineries add to the fuel to make it more volatile in cold weather.

Dano, like Dave said. Run a tank of 89 or better through it. See if you can recreate the same circumstance that caused the rattle to begin with.

Drive and don`t worry about it.

I know. That comes after a person attempts to change out bad lifters...That's why I presented the warning.

I would still pull the valve cover and do an inspection. Simple, easy, and doesn't cost a thing. Plus he can verify oiling. After having 3 AMC engines, I can vouch for the top of the valve train being problematic and worth a look.

 

[Dano]

Thanks to all, great info. I did remove the valve cover to do a visual. The rockers looked and felt in good condition. Started pulling all the push rods and found one that was bent! A friend say these rods can just go bad, warp or whatever, I ordered complete replacements (only 3 bucks each) but he advised me to note down which one it was just in case the tapping returns. He said if it does return, I'll need to dive in deeper into the root of the problem. Once a gain, thanks to all that reponded.
Danny

 

[fzsk4p]

Thanks to all, great info. I did remove the valve cover to do a visual. The rockers looked and felt in good condition. Started pulling all the push rods and found one that was bent! A friend say these rods can just go bad, warp or whatever, I ordered complete replacements (only 3 bucks each) but he advised me to note down which one it was just in case the tapping returns. He said if it does return, I'll need to dive in deeper into the root of the problem. Once a gain, thanks to all that reponded.
Danny

Good find Dano. Still do not understand why it was intermittent though.

Could you have over revved the engine at some point ? That might explain the bent pushrod

 

[Dano]

I don't think I did. Yeah it doesn't eplain the intermittent tapping. Especially when it would disappear for a few days before it would come back. As for the intermittent tapping, again I'm not a mechanic, but could the bent rod rotate (spin) in a way that when it reach a certain spot it would tap in its channel. Seems like there is plent of room in the cavity or would it make the rocker arm move cock-eyed? Also going to do a visual on rest of the jeep as soon as all the snow and ice is gone.
I just hope this will cure it. Thanks, Danny

 

[CJim7]

Yes, it's possible the pushrod could still rotate and in doing so, it could catch the cup of the rocker in such a way that it would make noise intermittently.

Did you inspect the rocker carefully? I would be inclined to replace that also or at least suspect that it could have also been damaged running a bent pushrod. Also take a close look at the pivot to make sure it wasn't damaged.

 

[Dano]

Good point. I'll double check and/or just replace the rocker. I'm also going to take all the other advice mentioned and give everything another look.
Thanks, Danny

 

[jeepboy45]

Yes, it's possible the pushrod could still rotate and in doing so, it could catch the cup of the rocker in such a way that it would make noise intermittently.

Did you inspect the rocker carefully? I would be inclined to replace that also or at least suspect that it could have also been damaged running a bent pushrod. Also take a close look at the pivot to make sure it wasn't damaged.

Jim,
I know this is an old thread but you seem to know about rockers. I'm finishing the rebuild of my 360 and was going to re-use the valvetrain. But my issue is that I dont really know if the pushrod ends or the cups in the rockers are worn. Its really difficult to know and I dont have a brand new one to compare. Is there any way to meausure one, or any telltale signs of excessive wear. I dont really want to throw $AMC 150 at parts that arent really necessary to replace if they arent worn.

None of the pushrods are bent.

thanks,
Brian

BTW: Dano, did your ticking problem return?