Well, I had been chasing down exhaust manifold leaks, and there were some, but that wasn't my real problem. That periodic pinging under load was a stuck valve...I think.

I was driving her home and the sound got really loud and she was running rough, like one of the cylinders died. I got her home, but no power to speak of, very weak. I don't think it's timing jump, it starts easily and idles but with some roughness. Any load and I get a loud noise, sounds like detonation, valve is sticking or sluggish or something. Seems like its running on five cylinders, or rather one cylinder is detonating with exhaust valve opening prematurely or stuck or something.

Checked the oil, clean as a whistle, didn't get hot when driving it home. No extraneous noises at idle like bearings, rods or bent push rods. I'll pull the head and check it out.

The symptoms have been when it was cold it ran fine, no pinging or whatever that noise was, but as it warmed up I would get that noise under load, uphills, slightly noticeable at highway speeds, but very subtle or not at all for some periods. I had dialed the timing back a few weeks back, no difference. I checked the AFR, it was good, not lean. Last night suddenly I was getting the noise even when I just started out from a stoplight. Nothing at idle when stopped, but any kind of load, even slight, I'd get a detonation noise, sounds like a bad exhaust leak but there were no carbon tracks last time I pulled the manifolds, they weren't leaking. It was detonation inside the pipes.

Anyone had these symptoms? Valve? Something worse? Seems like it's in the top half, in the head. Ahhhh! I've been having bad luck with slants. Time to switch to a small block v8? Somebody say something to make me feel better like, "a head swap and you'll be back in business...."

Brian

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Have you verified valve lash on all the cylinders? Could be a worn out adjuster loosening to the point of getting noisy and not opening the valve.

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Casually looking for a Clifford hyperpak intake for cheap.

If the air fuel mixture detonates in the pipe , maybe the timing is to late.
Is this the same engine with the distributer gear and cam gear malfunction
last year?

I had something eerily similar about 20 years ago. Started right up, even when buried in snow. Idled rough but never stalled, even turning the steering wheel lock to lock at a dead stop and taxing the power steering. But it felt like it was running on 3 cylinders, except at wide open throttle. Had a light "tick" at idle but nothing too loud (had to be listening for it) but when it warmed up it ran all right. Sucked fuel like the Concorde though no matter what. Surged on the interstate and couldn't maintain a steady speed even on flat land.

Turned out to be a cracked exhaust valve. Not cracked to the point of pieces falling off, more like the Liberty Bell kind of crack. Unfortunately something like that requires the head being removed to find it.

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If it was easy, everybody would be doing it.

This engine was recently rebuilt, about 5k miles on it. I'm thinking stuck open exhaust valve but yes I'll pull the head and report back. Sure hope it's not the cam. If an exhaust valve was getting stuck open, detonation in the cylinder would go straight to the pipes and make a tick. Under load, more gas/air, bigger detonation so more noise. Does that sound reasonable?

I hadn't thought of adjuster issue, seems like if the exhaust valve wasn't opening the detonations would be back firing into the intake.

I'll check the plugs first, pull the valve cover, maybe do a compression check before pulling the head.

B

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Another reason I'm thinking stuck exhaust valve is that when it was cold it didn't happen but when warmed up then it started happening. Seems intuitive to me that it was sticky, more so when hot. Engine had lots of power ran smoothly, then when hot and under load this issue arose, when going downhill no issue and on flats only slight ping/tick was noticeable. Of course now it's permanent, so whatever the cause, it's not periodic any longer.

Actually, I recall a few weeks back, I was driving on the highway and slowed for some traffic. As I decelerated I noticed it was running rough, but then perked up and nothing more for a week or so until now. Might have been stuck temporarily then. These symptoms suggest to me, and I pray, this is not a cam issue.

B

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While on the subject can somebody point me to the best head install, valve lash cold set conversation/tutorial on the boards?

thanks if anyone has it handy.

brian

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Valve lash settings can be different, for different cams.

For a performance Clifford cam, do an initial check to see where the lash is set now and then adjust from there... to even the settings out and do any fine tuning.
A good "ballpark" starting point is .016 intake & .022 exhaust but again, see where it is set now.

In your case of a loud ticking sound, you will likely find a valve that is way too loose. (.100 or more)
Make note of that valve, then trouble shoot for the problem.
(loose adjuster screw, broken valve spring, bent push rod, valve recession, loose seat insert, worn lifter, sticking valve, etc.)
DD

I have the lash settings for the cam. I'm hoping it's on the top half, not the lifter or cam...let us all have a moment of silence so the SL6 spirits can hear my plea...




b

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It was a blown head gasket. It ate through the gasket in two places at #4 cylinder, you can see it made "cross talk" between #3 and #4 (hence the rough running). I essentially drove it home on 4 cylinders.

http://s785.photobucket.com/user/67dart ... g.jpg.html

http://s785.photobucket.com/user/67dart ... w.jpg.html

http://s785.photobucket.com/user/67dart ... m.jpg.html

No bent pushrods, lifter surfaces look great, valve adjusters tight, no broken springs, valves don't look sunk or anything, oil is clean as a whistle. I may have gotten lucky. Can't say why it would burn through the head gasket like that, but there's no pitting in the pistons, just carbon tracks from the cross talk.

brian

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this is what all the lifters looked like...

http://s785.photobucket.com/user/67dart ... o.jpg.html

they were all turning during breakin, and they look like glass, cam lobes look great.

b

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Wow, that is an odd failure. I have never seen a head gasket fail like that. Maybe tiny debris left on a mating surface during assembly? Lifters look good!

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Casually looking for a Clifford hyperpak intake for cheap.

I'd be sure and check for flatness of everything while it's out. Did it seem like all the head bolts were tight? What type of head gasket were you running?

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

While it's a bummer that it failed it is always nice to get something apart and find an obvious source of the problem.

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