2002-2003 4.3 Vortec rocker issue

Need some help here guys. I have a 2003 Tritoon with a Vortec 4.3 I/O. Bought it used last fall and have had it out about a dozen times running about 200 gallon thru it. Last weekend, on Saturday, it ran like a top as usual. On Sunday, unloaded it off the trailer and was idling in the marina waiting on my wife to return from parking truck. And all of a sudden I could hear lifter noise that got increasingly louder. I thought first off that it might have a stuck lifter, but giving it a bit of gas made it worse. Then it quit. Luckily I wasn't out in the middle of no-where and got it back on the trailer easily.

Long story as short as I can! I took the engine out on Monday. Tore into it last night. Found the middle exhaust rocker (opposite starter) just laying on top of the tower. Bolt still in rocker but backed all the way out. I took the pushrod out and checked straightness. It was ok.

To back up a bit. After getting the engine out, I discovered it was a remaufactured unit. Nicely done, couldn't tell from looking at back of engine. Hard to see in the hull anyway. But ran fine the times we had it out.

Now for the problem at hand. I rotated the crank to get that cylinder to TDC compression and torqued the bolt (Yes mine has a bolt, not a stud and nut - roller cam) down to the recommended 22ft pds. What I noticed was the rocker pushed the valve down ever so slightly, about .125. Rotating the crank didn't help relax the lifter. SO I broke loose the intake rocker on the same cylinder. Keep in mind I checked the pushrod and it spun like it should. No pressure. The valve did not move when rocker was released. BUT when I tightened the rocker back up, same issue. It pushed the valve down about .125" . So I moved to another exhaust valve same thing...What gives. Why are the lifters not relaxing. What am I doing wrong?

I plan on taking the heads off tonight and checking the cylinders to make sure there is no other damage. It doesn't appear that there is anything else wrong other than the backed off rocker. Maybe it wasn't tightened correctly when remanufactured. The gas filter said 08-2008, so I'm assuming it was probably changed the same time the engine was installed. SO it has ran fine for about 2 years.

Sorry for such a long post, but I've searched these threads and there is not much info on the newer Vortec 4.3 heads.... Is there anything that would make the rocker bolt back out other than it wasn't tight to start with? The threads are perfect, not stripped in any way. At least 1" thread engagement. I'm stumped Any thoughts? Maybe the rest of the teardown will show something. Hopefully not, though. Hoping this repair is only gonna cost me a gasket set!

Re: 2002-2003 4.3 Vortec rocker issue

Can you post a pic of the rocker area ?

I just looked at 0L012009 THRU 0L618999 and it shows studs and nuts, not bolts.

Re: 2002-2003 4.3 Vortec rocker issue

Will do. When I get home from work. My Title says the engine model is
OM633076. Although the engine is a remanufactured one. The block casting number 14099090M dictates it was made somewhere between 2000-2005.

Re: 2002-2003 4.3 Vortec rocker issue

OK...Here are the pics, but I think I've solved my problem. Last night, before calling it quits for the evening, I torqued the three rockers down that I had loosened. All three compressed the valve by about .125". Today when I got home the valves were seated like they should be.

SO given that, it must take awhile for the hydraulic lifter to relax once the rocker is tightened. I believe I read somewhere online that there is a sequence to go thru where you put cyl # 1 at TDC and torque a certain amount of rockers. Then rotate crank 180? and torque the rest. This makes sense now to allow all the lifters to relax before turning the engine thru to keep from bottoming out the springs. Just my theory. Maybe someone can confirm.

I'm off to the garage now and do a compression check. If its good, I'll put the intake back on and forgo taking the heads off. Just call it a fluke on the backed off rocker and see how it runs. Still baffles me how it could run so long and all of a sudden have a rocker loosen up to the point of falling off the tower?

Re: 2002-2003 4.3 Vortec rocker issue

Were any more of the rocker arm bolts loose? Somehow I would bet they were improperly torqued from the beginning.
Here is from a Volvo manual that covers that style rocker arms.

Re: 2002-2003 4.3 Vortec rocker issue

and here again, loctite 571 or the permanent red can be your friend even though ts not called for.

Re: 2002-2003 4.3 Vortec rocker issue

No other rocker arm bolts were loose. Although, after checking the torque of all the bolts on both heads, the ones on the port side were not as tight as the ones on the starboard side by a few pounds. Interesting. Since I just acquired this boat last fall and one of the PO's had to put a new engine in it, I'll never know the exact history of it.

All is good. I checked the compression and all cylinders are OK. No backlash in the gears and chain. So I'm going to put the intake and manifolds back on and see if I can get it back on the water by this weekend. Anybody ever work on an Inboard on a Pontoon? Not as easy as it should be. Took longer to get the seats and engine enclosure out than to pull the engine. Maybe the newer ones are engineered a little better!

Thanks for the help!

Re: 2002-2003 4.3 Vortec rocker issue

yes, I do a few.
wish they would sink.
every time they question the labor.
have to remove the dang hull to access anything.
and NOTHING lines up properly for reassembly.