454 died, now it sounds like it's eating itself!

The kit boatbum linked is the type for this job. It concerns me that the description in the link says #6 fits 14mm and doesn't mention 9/16", which is what those manifold bolts are (or at least started out as). I pounded a 13mm six-point onto wasted 9/16" manifold bolt heads and being able to get them out. Naturally I had to have a socket that would grip, but I think the pounding went a long way toward getting them loosened.
 
That welding trick is something I always wanted to try but I've never run into a case that I couldn't remove the bolt, though I have all the welding stuff.

Trying to think of a cause and I came up with broken connecting rod(s)...sorry!
 
Thanks again for all the replies! I didn't mention it, but we did try some easy-out deep-well sockets. Basically like the Craftsman ones that Sandy and others linked too... They have sharp, curved ridges (left hand threads) inside and are designed to be hammered onto the bolt heads and then they bite in as you try to loosen the nut. Very cool idea, but they didn't work. Couldn't get them to bite in at all, no matter how much we hammered.

The Dremel tool idea didn't work either. Not enough clearance to get the tool in there! (UGH...) Fortunately, my son's Father-in-law runs a large repair shop for trucks and buses, so we pulled the boat over there and one of their mechanics went at the engine with a fire wrench (oxy-acetylene torch)! In just under 10 minutes we had both exhaust manifolds removed. Yay! With the manifolds removed it was easy to get at the remaining bolts holding the heads in place. So we removed the rockers and the push rods and then pulled both heads. Unfortunately, this is what we found on the port side:

http://imgur.com/AtoBrAA

That is what is left of the # 5 piston. And yes, you can also see where the head gasket failed between cylinders 3 and 5. But that missing chunk of piston in the upper right corner is a real problem. (Look closely and you can see the compression ring showing!)

So, yeah... the engine has to come out of the boat. (crap) Originally we said if we had to pull the engine we would replace it with a reman. However, after speaking with his father-in-law, we're starting to come around to the idea of pulling the engine and rebuilding it ourselves. There's no signs of cylinder scoring, and all the other pistons look good, so it should be a fairly simple rebuild. He's got all the tools and equipment we need, plus a handy 15 ft lifting frame with a pair of chain fall hoists to yank the engine with. Of course, we have to pull the outdrive first.

General plan right now is to do a set of rings and rod bearings plus replacing the one bad piston, then refurbish the heads and put new exhaust manifolds on when we bolt it all back together. No plans at this time to mess with the crank, the cam, or the timing set. Oh yeah, and we'll need to replace the exhaust flappers in the Y pipe too - they were completely burned away.

I've been down this road before with the 4.3L in my old Bayliner, but this will be our first time rebuilding a big block. Fortunately, my son's Father-in-law has a pretty nice shop, and lots of mechanics to help out when we get stuck. It's just going to take a lot more time this way...

Adam

PS: I gotta say - using the torch was genius. It took him longer to get set up in the bilge than it did to blow the bolt heads off. Heat them up, hit the cutting oxygen for a few seconds, and done! Very cool... I'm going to keep that in the back of my mind for future reference.
 
Sorry to hear it was not the easy fix we were all hoping for but at least you have a game plan. Best of luck keep us posted.
 
I'm curious what put that hole in the piston. There's no other obvious damage to the head of the piston. Did you find the piece that broke off? Try turning the engine over as you observe the movements of the pistons.
 
I was going to wager hydro lock since the valve train seemed to operate based on their viewing it. But not having any water in the oil pan disputes this. Sticky valve? But they still worked so maybe it wasn't bent.
Hopefully the block gets stripped down and cleaned up for a complete rebuild. There is sure to be debris floating around.
 
Adam - That's a big shame the piston turned out to be holed , but your pic is confusing me. It looks like there is a big chunk out of the cylinder wall too. Is that just a mirage caused by a reflection off shiny walls I hope I hope.

I was very reluctant to suggest what you call the "fire Wrench" (love that) which a lot of pros use for that to save a LOT of time. The idea of having that hot flame and melting steel in the engine compartment kind of gives me the willies. But it's terrific you got the manifolds and head off and finally confirmed where the Bad Noise was coming from.

May things go more smoothly as you work back to the plus side !
 
Charlie: We are unsure what caused the demise of the # 5 piston. We have a few competing theories. The first one is basically the catastrophic failure scenario: the engine cross-fired due to a corroded distributor cap which blew the head gasket and damaged the piston due to extreme pre-ignition. The second one is that it happened in stages... First the gasket blew, and then sometime later "something" happened to the # 5 piston. And the third one is that the piston was damaged when we bought the boat and we just never noticed, at least until the head gasket blew...

Currently I'm starting to wonder if water ingestion might be involved after all, as Boatbum suggested. I mentioned above that the Exhaust flappers in the Y pipe were totally gone. So it's possible that water could have come back up and into the engine. (It sits very low in the bilge!) Also, if you look at the picture I linked to above, you'll see the # 5 piston is very clean. All the other pistons (and all the valves) have the normal dusting of carbon residue on them, but # 5 is very clean, and so are the valves on that cylinder. That strongly suggests water to me.

The crazy thing is that there isn't any sign of water anywhere else in the engine though. So if it did swallow some water, it was a tiny amount. But maybe that was enough to do the damage.?. I honestly don't know for sure.

Sandy: I actually took a class in oxy-acetylene cutting and brazing when I was in the Navy, but that was nearly 30 years ago and I haven't had a torch in my hand since. Plus given how cramped it was in the bilge, there's no way I would have trusted my skills to get the bolt heads off without causing a serious fire. (I share your concern for having fire anywhere near a boat!) Fortunately for us, the mechanic who assisted us knew exactly what he was doing, and the welding blanket we used managed to contain all the slag and sparks.

Regarding the appearance of a chunk of the cylinder wall missing - that is indeed an illusion caused by the mirror glaze finish on the cylinder wall. It's actually very smooth. (No apparent scoring, which is nice.) And we did find some tiny bits of piston material... (There are a few visible in the picture if you click on it to get to full size. Look at about 7 oclock and you'll find some.) Interestingly, I found a few pieces on the other side of the engine as well, which seems to suggest that the piston crown may have failed a while ago.

It appears that despite the damage to the piston, the compression ring is still seated and holding. At the very least, that cylinder still holds oil on top of the piston... So it's possible that these things are not related. That piston could have failed at some other time. We probably will never know for certain. But I do know that the entire valve train looks great, and all the push rods were straight and undamaged. If the engine swallowed water, you'd think the valve train would be bashed all to hell.

Eh - I guess we don't really know what all happened. But for sure we know what has to happen now: that beast needs to come out. It will probably be late next week before we have time to attempt that though. :(

I'll be sure to keep you all posted on our progress.

Adam
 
It looks like it is a reflection on the cylinder wall. But, the question is - where did the chunk go? It looks like the top of the piston took a beating, so maybe the chunk broke up into small pieces and exited via the exhaust. On top of the rings and bearings, you need to thoroughly clean the oil passages of the block because of all of the metal that went somewhere. Also, replace the oil pump and the timing chain/gear while you are at it.
 
Not unusual for a big block to do this. Third one I have seen. At some point the engine sat too long and the cylinder wall lost lube coating. It broke at the tightest point. It is why it important to "pickle" if you lay up an engine for a prolonged time. See it a lot on a/c engines with tapered cylinders.
 
Damage is close to that valve relief pocket in the top of the head. Makes me wonder if a valve stuck Open and the piston smacked it. You're going to be doing a lot of work. Please be sure the timing set, chain and sprockets, are good before you button it up. Or just install a new set.
 
That clean piston is a sign of running with water ingestion. The valve could indeed have hit the piston and caused the damage but usually there will be a lot of dings in the piston and head from smashing the chunk.

The head gasket is pushed out of place on the right side. none of that accounts for the low compression elsewhere.

still wonder about valve timing.
 
Water or AF will clean a piston. This is an indicator of a leaking injector tube in 2 stroke detroit diesels.
 
"Where did the chunk go?" Yeah, we wondered that as well. We did find tiny pieces in other cylinders, but not enough to make up all of the missing material from the crown of the # 5 piston. Evidently it is common for pieces to travel through the intake into other cylinders, but it is very *uncommon* for those pieces to get into the lower half of the engine. I guess we will see soon enough though, because on Thursday we plan to pull the engine and have a look for ourselves.

First order of business will be to drop the oil pan and see what's in there. Will probably pull a sample to send out for analysis too. Then we'll flip it over and start looking for other problems.

Interesting concept about the piston breaking from a lack of lube following a long period of non-use. If that is what happened here, then the piston likely failed quite a while ago - possibly a few years. (The guy my son bought the boat from actually used it rather often, while the original owner basically just left it sitting at the dock all the time.)

We did hose it down with seafoam and shot oil into the cylinders before we called it a day when we pulled the heads, and we will keep it lubed throughout the rebuild process to prevent any rusting.

Regarding damage to the valves on that cylinder - here is a picture of the head on the port side:

http://i.imgur.com/vkXVZBt.jpg?1 (Click the image to zoom in)

You can clearly see where the head gasket blew between cylinders 3 and 5. And yeah, the valves on # 5 do show very slight scratches on the bottom of the tulip, but nothing really severe. They are blasted clean, however, which none of the other valves are. So, like so many others here, we are strongly concerned about water ingestion being an issue.

Here's the puzzler though: The gasket on the port head appears to be completely intact between the water passages. So if water got in, it just about had to come from the exhaust system, and if that were the case it should have affected more than one cylinder, right? So how come only cylinder # 5 is completely carbon-free?

Here is the album of all the pictures of the engine for comparison:

http://imgur.com/a/4dZQP

We did notice that the port side head gasket was "shifted" aft, and we don't really have a good explanation for that. It could have happened when the gasket failed, or it could have been a lousy installation job a long time ago. No idea if it's related to the failure or not.

Valve timing appears to be correct, even after everything that happened to the engine, but I guess to be thorough we really should pull the timing cover and check the timing set. (That's the part I'm afraid of... No good marks on the engine now, at least not that I can see, and thus re-setting the valve timing might be tricky if we start replacing things in there.)

I should know more by the end of the day on Thursday, and I'll update things here once we're done for the day. Thanks again for everyone's input!

Adam
 
OK, so the engine is out of the boat and on a stand, and we've pulled the rod caps and removed all the pistons.

The good news: the cylinders are in great shape. No scoring, and no ridge either. (Pistons came right out!) The rings looked really good on all but two cylinders. The top ring on the bad piston was seized, and there was another cylinder that had one partially seized compression ring as well. But the bottom rings were still OK. Also the rod bearings were in great shape, as were the journals and caps. No metal bits in the oil, although there were some very fine ferrous bits on the magnet for the oil pan plug. Not much, and they were super tiny, but they were present.

Right now the plan is unchanged: Replace the bad piston, install new rings, replace the rod bearings and oil pump and put the engine back together. The heads have already been dropped off at the machine shop, and we have new exhaust manifolds and exhaust flappers on order. Full gasket set is already here.

Now the bad news: it seems that buying a single piston for this engine is going to be prohibitively expensive. It's a flat-top, cast piston with "12555417" stamped on top, and it has two valve reliefs. Evidently that part number was discontinued ages ago and has been supplanted twice. The best quote we've gotten so far was $220 for the new version. (Ouch!) And then we need the rings. And there is some question as to whether the rings for the old pistons will fit the new ones.

Since we still need a full set of rings for all cylinders plus new rod bearings, we're starting to think about replacing all 8 pistons vs trying to buy just one. It seems that the "all in one" rebuild kits are quite a bit cheaper vs buying things individually.

My main concern is weight. I don't know if the new pistons weigh the same as the old ones. Although having one different piston would be bad enough, having all 8 either heaver or lighter might be a disaster. I think we need to do some more research before we buy anything.

What do you guys think? Most of what I've looked at on-line so far has been from Summit Racing, Falcon Performance, and Mabbco. Should I be looking elsewhere? (Sure wish George was still around...)

Adam
 
eBay might surprise you. My quick search was disappointing, though.

A friend tinkers with 454's. I'll ask.

What about your machine shop? Surely they do rebuilds and need one or two pistons.
 
When my 1994, 454XL Crusader was rebuilt, all 8 Pistons were replaced despite only one having a hole in it. Same # as yours. Apparently this is pretty common with this engine. The rebuilder knew which piston even before he was told.
 
Reading Gregory, I wonder it those pistons have a design compromise that sets them up for failure. It's a racer's trick to place the top compression ring closer (than stock) to the top edge of the piston. This tweaks the compression ratio just a tad. OMC tried that in the 1970's and top edges came off lots of pistons. OMC blamed the gasoline changes in those years but provide at least a set of new pistons. Sometimes a full overhaul. I'm guessing the "new" pistons were the former style, with more piston margin above the top ring...
 
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