Sucked a Valve!
 

Ok, there I was running a smoth 3900 rpm on my freshly (35 hours now) totally rebuilt Gen IV 500 hp 454's when all the sudden the strabroad engine quites, just that quick. Opened the hatch, nothing apparent. Tried to bump it over, locked up tied. Pulled a valve cover, rocker arm (intake) on the #7 cylinder is pushed toward the intake manifold off the valve stem, keeper for the valve is laying on top of the head & valve stem comes way up.

Long story made short (2 hours back to the dock an a couple of hours of disassembly) I find the head of teh valve lodged side ways in the head, broke right at the base of the stem & the engine was full of water. Drained the oil & water, lift rod bend to hell. The valves were beginning to make some noise but didn't really seem like that much to me, solid lifters, never again. First, how'd teh water get in all the cylinders? Second, what usually cases that kind of failure or is just simply part of the game? I plan to have the engine pulled Tuesday. Anything (other than the obvious, fix what's broke) I should have them do? Thanks.

Al

Re: Sucked a Valve!
 

Look at your cam lobe separation, it sounds like reversion.

Re: Sucked a Valve!
 

Thanks for the response. While I'm a reasonably go wrench turner, I don't have alot of tech experience. Could you give me the Readers Digest version of "reversion"? Al

Re: Sucked a Valve!
 

Reversion is when a (usually) larger than stock camshaft is used, and the valve overlap causes a momentary suction pulse on the exhaust side. This momentary suction pulse can suck in exhaust cooling water if the water entry point is not far enough away from the point where it joins the exhaust gas in the pipe or hose. The most likley case is when one uses stock exhaust manifolds, or if you pull the throttle back quickly where the boat comes off plane and the water wave could push itself into the exhaust pipes. This is likley what happened, as the cold water hit your hot exhaust valve, cracking it like glass. I'd go with 8 new exhaust valves and move the water entry point further downstream by using different exhaust elbows. If your piston in #7 is OK, this should take care of you.

Clint

Re: Sucked a Valve!
 

Poor quality, necked down valves will cause this. Use manley severe duty exhaust valves at a minimum, extreme duty prefered. Water in the engine during valve failure on a marine engine is automatic (wet exhaust). This is because during failure the exhaust valve so longer seals and the piston begins taking big gulps of water on the downward strokes. That should explain your water intrusion.

If the valve was shattered into little pieces I would be concerned with leaky risers or reversion. They get brittle from the constant quenching of the water on the hot valve. That doesn't sound like the case so I would assume no problems there.

BT :cool:

Re: Sucked a Valve!
 

Thanks guys. The valve that failed was an intake. Does the same principal apply with an intake valve failure. The exhaust system is SS Bandit series 4" silent choice marine exhaust, B/B stainless steel risers with B/B Exhaust Manifold, black with hard coat for saltwater. While they appear to have a pretty good rise, I can see the "coming off planes scenario" happening.

There was water inside the exhaust manifolds and in the intake manifold itself. Here's a photo of the valve lodged in the head, ouch. While I've gotten most of the water out with a shop vac, unable to turn the engine over (manually of course) so I am unable to get the remaining cylinders to push that water out, I presume it will be ok till I get it to the shop Tuesday. Thanks again for the response, that's what I love about this site, everyone seems to be willing to share there experiences which makes at least let's you know, your not the only one and it really is just part of owning fast toys.

Re: Sucked a Valve!
 

Is the valve stem bent? If not, then the head just snapped off. If the head is bent, maybe the valve guide is worn and the valve stuck open for a second. In my experience, the intake runs much much cooler so it could not fracture like the exhaust. If you have an aftermarket cam, they close the valves much harder than stock. There is a lot of science into valve closing for engine longetivity and to prevent the valve from bouncing off the seat when closing fast. Sounds like the stem is straight and the head snapped off.

Re: Sucked a Valve!
 

Not sure if the stem is bent or not yet. It slides up and down ok, unable to pull it out through the top, will pull heads Monday once I'm at the shop. I'm also not sure what kind or how old they are; maybe the result of metal fatigue.?. I'll see what the shop says but I thinking I replace them all with a heavier duty quality valve, at least I know what I'm starting with.

That was the problem with this boat when I first bought it. While someone spent a lot of money rebuilding it in 1998, it wasn't taken very good care of after that. While unknown at the time, it became quickly apparent that the engines were run out. This particular engine had all kind of problems including crack heads, intake manifold & piston rod. It was a newer engine (or at least the block) than the other, like 6 years newer based on the serial numbers. Now that I think about it, the heads and manifold where one shade of purple (matched the other engine) and the block was a lighter shade of purple. Back then, I figured they changed the block for some reason, but since the heads and manifold matched the other engine, they must have used the ones off the old engine. The bell-housing had some surface rust at the engine the port engine was perfect, no rust. Thinking of all that and this somewhat unusual failure, maybe the original engine overheated for some reason, they trashed the block using the same intake manifold, heads (valves and all) and what I have here are valves that have seen some extreme heat somewhere in their life time that simply lead to this failure. I'm changing all of them and moving on. After untold hours of tender love and care (and the wife wondering if I had moved into the boat), the boats in top condition stem to stern, well except this minor set back. THANKS GUYS!

Al

Re: Sucked a Valve!
 

I had a problem like that with a set of Merlen heads. The water jacket around the exhaust port had a pin hole hence water cooled valve. Drove me absolutely crazy for an entire season trying to figure how water was getting into the cylinder. At the end of a season, it let loose and destroyed the engine.
On another note, check the exhaust ports of #5 & #7. They have a tendancy to corrode and wear thin. I had this problem recently with a stock pair of GM heads #990 castings. The 990's are no longer available through GM and may need to go aftermarket. Merlins are very available but would choose Dart with the marine coating. The Darts may be on backorder as of now due to popular demand. The nickel content in Darts are much more than Merlin resulting in longer life.

Re: Sucked a Valve!
 

You won't get the water sucking when an intake valve goes. You can tell by looking at the breakage if it was a fatigue failure or a impact failure. There will be a "shear ledge" across the breakage with an impact failure. The breakage on fatigue failure will appear rather uniform.

Take a close look at the valve stem in the keeper area. See if there are scuff marks on the valve stem. There should be no scuff marks as the entire valve assembly should be locked together. If there are scuff marks the valve was floating and you have either a harmonics problem or the valve spring was tired.

BT :cool:

Re: Sucked a Valve!
 

My guess is that your cam has to much overlap for the silent choice exhaust. The SC exhaust dumps the water into the exhaust very close to the engine to accomodate the "Y" diverter. If your cam has much more overlap than the stock engine, your choices will be to either eliminate the silent choice with straight pipes to dump the water further downstream into the exhaust or change the cam to one closer to stock with very little overlap. The water that's getting into your engine is probaly not coming from outside the boat but from inside the engine as your cooling water dumps into your exhaust stream.

Your choice is probably going to be between a louder boat that doesn't have silent choice or a boat with slightly less performance by swapping out the cam for something abit tamer. I would be concerned that you might fix the engine only to pull water back (potentially breaking another valve or worse) into the engine because of the silent choice/cam combo you're running. Just my $.02.

Re: Sucked a Valve!
 

The water is probably from a split cyl wall of damage to the head from the valve pieces.

I have repaired the same engines for the same problem for other people.

Re: Sucked a Valve!
 

I hate it when I cannot edit posts to correct brain faster than the fingers.

Split cyl wall or damage to the head is what I intended to type.

Re: Sucked a Valve!
 

Well, pulled the engine today, removed heads and oil pan, what a mess. Valve head went through the head rupturing water jacket which is why the engine filled with water. Apparently it ran long enough to pump water to all cylinder and hydro-locked bending piston rods. Parts of head from #7 cylinder found in cylinders 1 & 6. steel shavings found in pan, believed to be from pistons. All from an intake failure (appears to be fatigue failure) in a matter of seconds. The shop will finish their assessment tomorrow, looks like it's back to the drawing board.

They were running so good and only 35 hours, oh well. You can bet we're going back with serious quality valves this time! Shop is recommending stainless, any thoughts?

Al

Re: Sucked a Valve!
 

You are lucky that you are not sleeving the block. Not cost wise but durability wise.

Severe duty intake valves and Inconel exhaust valves.

Good quality springs like Isky 8205 Plus.

Re: Sucked a Valve!
 

Well, not so fast, #7 was cracked and will need to be sleeved. Basically they are telling me:

2 - rods
2 - TRW pistons (.030 over)
Set - Rod bearing
1 - 990 GM head
2 - new valve (told them no way all new serve or extreme duty SS valves)
Sleeve #7 cylinder
Of course the usual stuff that goes with taking one down and putting back together, i.e. cleaning, mag-flux for cracks, gaskets, etc.

I removed all accessory leaving a couple of motor mount bolts hand tight, took the boat to their shop, they lifted out of the boat. They will drop it back in the boat and I strap on all accessories.

Does that sound like a nice round $3,000.00 job to them? Maybe it is I simply don't know. What do you guys thing?

Al

Re: Sucked a Valve!
 

Sounds like a fair price to me.