455 Olds, started clattering up top and had a loss in power.
Finally got around to pulling the valve cover and found that cyl #2 has a very loose rocker arm, on the intake valve, with lots of lash at the pushrod/ rocker arm.
while running, the push rod does move up and down but just rattles around and barely moves the valve.
Very little to no oil coming from pushrod.
compression test on all cylinders were consistent, not outstanding, but consistent on all cylinders except the #2, that was down to 95psi.
Just looking for thought on what could be going on?
Collapsed lifter?
flat cam lobe?
it would have to be very very flat to have that much lash in it, wouldn't it?
valve not closing for compression loss?
I will pull the rocker and push rod off tomorrow and the intake off in the next day or so to have a gander at the Lifter and possibly the cam lobe.
Have not done a leak down or air test to see is valve is leaking, yet, but I'm almost sure it has to be.
i have a video of it but not sure if can post vdeo?

 

Rockers and bridges do wear, replace that set 1st and see then what you have.

 

After you do the disassembly you will likely learn what the problem is. Please let us know.

 

Inspect the push rod to see if its bent. You can swap the rocker/s and perches as an assy with each other to see if the problem moves, if the problem does not move then you need to remove the intake manifold and inspect the lifter/s and cam lobes. Chances are the lifter is worn on the base where it contacts the cam, possibly worn through to the point of leakage and will not build pressure. If thats the case, the cam lobe may also be wiped out.

 

Check closely for a broken valve spring.

 

When you get the intake off, pull that lifter. If the bottom of the lifter isn't baby butt smooth, the cam has wiped a lobe.

 

Well pulled the rocker off today and found that the pushrod is bent!

It is bent so bad, that i cant even get it out of the hole!

 

You need to pull the intake and inspect the lifter and cam lobe and also determine what cause the bent pushrod, while there you might as well look at all of them.

 

Yes Sir, that is on the agenda for tomorrow.
Keeping my fingers crossed.
Something is telling me there might be a problem with that intake valve, since the compression is so low in that cylinder.

 

Low compression because the valve won't open?

 

Ahhhh, Right!

 

Ok so i pulled the intake, and low and behold the pushrod was curled like a cheese puff!
No chunks of metal, no glitter! Pulled the lifter and its not collapsed, its not worn out, the plunger is not loose, the foot looks normal, not worn, still nice and smooth.
the camshaft lobe does not appear to be flattened out.
The valve spring does not appear to be broken, the valve moves up and down freely, with a tool.
i just don't see any apparent reason for the bent pushrod! Confusing!

i got all the parts to go back together with it.
intake gaskets, new pushrod, new rocker, new lifter.
I'm guessing, i will put it back together, with the new parts, except for the new lifter, as the existing one has no damage and is already broke in to the cam, unless any one has any other ideas?

 

Whats the spark plug look like from that hole?
Do you have a bore scope?

 

i guess a little oil fouled, but not much unlike all the rest of the plugs.
i do not know when the last time plugs were changed.
This is a recent engine to me, so i dont know the maintenance history.
for all i know the pushrod could have been been bent a little and bent more when we ran the engine.

i know the engine was said to be getting tired.
i checked the compression and all cylinders have 125 psi except that particular cylinder was at 95psi, all after the bent push rod.

unfortunately, no i don't have a bore scope.
i have thought of taking a look inside.

 

A little back story.
this engine is in a 1974 jet boat.
purchase recently. The engine was advertised as starting to get tired as it has lost some compression.
Ran the engine, then took it out on the water.
seemed to run ok.
Took it home, and had to rewire entire boat.
finally took it out for a weekend.
Saturday it ran decent all day long, with no issues.
Sunday we launched, and got out of lagoon and onto river, and up on plane, after a few minutes, the engine started not sounding to good, top end valve train clattering, and then loss of power, prolly when pushrod bent.
got to where we were going, that was not to far and shut it down.
towed it back and had not ran it until the other day to see what it sounded like and then tore it apat to where i am now.

 

How old was the gas in the tank? Varnished fuel is like glue that cause things to bind up. The other issue could be the timing chain set, but you said the engine ran until you turned it off.

 

Any water in that cylinder?

95 psi cranking compression is pretty horrible. Even so, the cylinder should run. I tested a '75 Ford 400 that had 50 psi in one cylinder, it was dead at idle, but ran at higher throttle openings. I had a boat 454 with 80 psi cranking compression, and that cylinder ran even at idle. The engine was gutless, though.

OTOH, once the valve can open, compression may return to normal.

Yeah, stuff a fresh pushrod in it, dump some Techron in the fuel tank, run it and see what happens.

 

fuel was at least a season old, as it had sat for at least a season, so more than likely at least a year. Could have been more.
tanks weren't full and i did mix fresh gas with it at least a half tank in each.
yes the engine never did die. It ran untill shut down and even had fired up and idled fine, later after that.
even started and idled fine, for a couple minutes, the other day before i tore into it.

 

No water in cylinder no milky oil.

Yea I'm hoping compression will come up with new pushrod, too!

All the other cylinders have a consistent 125 psi compression. I know thats not outstanding but a lot better than 95, lol!

 

None the less, its going back together, as we speak!
We will see how it runs tomorrow!

 

Alrighty then! The Olds is back together and sounds and is running pretty good!
The compression in that hole even came back op to 135 psi.
it ki da bugs me that i dont know what caused the pushrod to bend, but i could not see any reason for it.
who knows, it could have already been slightly bent before i got it, and bent more after running it.
i guess we will see if it happens again

 

Lol, i have no idea why all that was underlined😬!

 

I was wondering that too?

some guesses high rpm, loose rocker? Wrong size, weak rod?

hopefully someone will chime in as to some possible causes.