possibly lifter/ cylinder out

[Four86Winns]

After cruising, and a little WOT, I slowed down to go through a shallow section. Suddenly, my engine (3.0 liter GM) started making a rapping sound. I shifted in to neutral to check it out, and it stalled. I started back up, after much difficulty, and now I find that one cylinder is down, and the rapping sound is somewhat prominent, but nothing like a rod. A very experienced mechanic towed me in, after listening to the motor he said it sounded like it might be a lifter. Is that possible? I have yet to check for spark, although everything in the ignition system is very much intact, and the spark plugs look fine. Checking spark is on tomorrows list of to do's. Any other ideas?

 

[sea wolf]

Re: possibly lifter/ cylinder out

Open your wallet. Did you have it redlined? You have an engine over 20 yrs. old & you ran it wot. For how long?

 

[180shabah]

Re: possibly lifter/ cylinder out

Time for a compression test.

 

[Silvertip]

Re: possibly lifter/ cylinder out

Let's do some checks before you sulk off thinking the world has come to an end. Push rods have been known to wear through the rocker arm. rocker arm sockets have been known to wear through, and lifters have been known to collapse. Since you apparently know what a connecting rod or main bearing rap sounds like, did you happen to notice what the oil pressure reading was when the noise appeared? If its low (say less than 10 PSI) you have a bottom end problem. However, the quick check would be to pull the valve cover and simply look at and feel each of the rocker arms. Try to raise and lower each push rod. If you find one or more that's sloppy, you identified the problem. Lifter (change through the side cover), push rods, and rocker arms are inexpensive (in relation to everything else marine). Be sure to properly adjust the valves when any repair is done. Don't just tighten the nuts down.

 

[Bt Doctur]

Re: possibly lifter/ cylinder out

Pull the valve cover and check for all the valves. Just had the same motor break a spring and drop a valve into the cylinder.Luckily, It just took the valve, no head or piston damage.

 

[Four86Winns]

Re: possibly lifter/ cylinder out

Everything was actually fine, a small rivet, looked like from a snap got stuck in the valve, and wedged it open. Just need to put in some new gaskets and put it back together. Is there a difference between marine gaskets and auto gaskets? Also should I put new head bolts in? They're black so they're hardened steel so can I put them back in? Thanks. Should be back on the water by the weekend knock on wood

 

[Silvertip]

Re: possibly lifter/ cylinder out

Make sure you use sealer on the head bolt threads as some of them pass into the water jacket and will leak unless sealed.

 

[FreeBeeTony]

Re: possibly lifter/ cylinder out

I would be more worried about as to where this rivet came from and why didn't it fall into the cylinder?

 

[Coors]

Re: possibly lifter/ cylinder out

Are you now missing a part from the throat of the carb?

 

[Four86Winns]

Re: possibly lifter/ cylinder out

Have not been able to figure out where the rivet came from, but it didn't solve the problem anyway. After getting it back together there was still no compression. So I took out the push rod on the "bad" valve and it shut enough to give normal compression. Took apart the lifter, and although it didn't have the ball bearing, as described in the book, in it, everything else was in place. Repacked it with oil, put it in, still clacking, changed lifter to another valve, the sound didn't move, so its not the lifter. Had a mechanic give another listen and he said the knock sounded like a bad spring, Although EVERYTHING is in place and looks fine. Maybe the internal spring broke, or the tension is off. So next step is a new spring. Thought about the cam, but everything else is moving properly, and through the lifter hole the lobe looks fine. At least there's compression so its not a cylinder or piston.

 

[Coors]

Re: possibly lifter/ cylinder out

I hope you put the lifters back to original places.

 

[Four86Winns]

Re: possibly lifter/ cylinder out

yeah I did, it was just a test, to see if the sound moved to a different valve.

 

[Four86Winns]

Re: possibly lifter/ cylinder out

I'm assuming due to lack of posts, I'm not the only one baffled. I've gotten 4 proffessional mechanics opinions and no one can figure it out.

And here is the latest digger...

Put new spring in, and new push rod in, sound went away, sounds perfect. Set valves back to where they were before (just temporary)

Reassemble everything, valve cover linkage, etc. Put on exhaust manifold, just for ****s, check compression. CLANK CLANK CLANK, the sound's back, only cylinder 2 exhaust valve, sound emanates from just under the rocker arm, although the rocker arm is PERFECT because as previously posted it was switched out with the neighboring one and no difference, same sound, same place. But still have compression.

Fire it up anyway, runs well for about a minute, then the cylinder went out again. Back where we started.

WHAT IS WRONG???

so talked to another mechanic, suggested to check the oil ports in for the lifter, maybe they're clogged once lifter runs out of oil they collapse. Makes sense but last time when we opened up the lifter it was hard and full of oil Whatever I'll check it anyway, cause when we were cranking it without the lifter to catch a glimpse of the cam, I don't remember seeing oil squirting.

Sorry for the length, just trying to be thorough, any other ideas. PLEASE???

 

[FreeBeeTony]

Re: possibly lifter/ cylinder out

What about the "washer" under the acorn nut holding the rocker arm in place?
Could that be damaged somehow?

 

[Four86Winns]

Re: possibly lifter/ cylinder out

Checked that, when I switched the valve spring (and everything else with it, rocker arm, washers, lifter, push rod) to the next valve over. The clacking remained in the same valve (exhaust) and same cylinder (#2)

Thanks for the suggestion though, I'm open to anything

 

[FreeBeeTony]

Re: possibly lifter/ cylinder out

What about the stud? Is it pulling out of the head?

 

[Four86Winns]

Re: possibly lifter/ cylinder out

Finally figured it out. The valve was slightly bent (not able to be seen by eye) and the head was warped slightly. Sent them to the machine shop, the head came back completely new all the valves checked and reseated. He only charged me 125.00 and offered to come up to adjust the valves, as he knows a trick to do it without starting the motor. Put it all back together, and it still didn't cure the problem. He comes down anyway, and finds that its the cam. The exhaust valve (the problematic one) opens twice as fast as it should and opens twice per stroke hence no compression. The cam walks back so it must either be broken or the retainer that holds it in with the gear in front is broken.

Either way still need a new cam because it is worn now. How much do marina's normally charge to install a new cam, assuming nothing else goes wrong. If its over a grand I'll probably end up attempting the job, doesn't look TOO bad.

Also how are the timing gears on the shafts? Pressed? I looked in the book but couldn't find it. Anything else I should know?

Thanks so much, 8 mechanics later, and however, many of you on here, at least we know whats wrong now.

 

[180shabah]

Re: possibly lifter/ cylinder out

If its over a grand I'll probably end up attempting the job, doesn't look TOO bad.

If it is over a grand replace the engine.

 

[Daddy O]

Re: possibly lifter/ cylinder out

The gear on the cam is pressed on. The machine shop that did the head work should be able to change it out for you. If I remember right the crank gear is steel so it shouldn't have to be changed, because the cam gear is some sort of composite.

 

[Coors]

Re: possibly lifter/ cylinder out

Why a marina? Let the machine shop do it.