10 Meter 454 knocking... Ugh!!

[Lumpy]

OK, I replaced the points on my 1986 454/350 Crusaders Friday night. Some history: The engines run great but I haven't really tested them over 3200 RPM which I won't get into now. On several occasions the port engine would start to lose power and the rpms would start to drop down to 2500 rpms. I'd back down to 1500 and she would run fine. I figured it was the points. (I already changed the plugs/wires/rotor cap distributor cap) So, I ordered the electronic ignition conversion kit but to shorten the story found out that they don't make a kit for the metal case distributor, only the aluminum. This is what the distributor told me. So back to Friday night, finished changing the points and timed both port & starboard. They started up quickly an sounded great. I then needed to do a sea trial so I took her out. I put her on plain and took her up to 3500 rpms and she was purring. Bumped up to 3800 rpms and she sounded great with those 4 barrels wide open just humming along. I must say she was moving out very nicely. I went back to the dock and shut her down sounding great. Now today, got the whole family on board, I fire up the port engine and immediately I hear a loud knocking. Took the value cover off and it's not the rocker arms. I'm thinking it could be three things. Cam lifter compressed/failed, journal on a piston or the main bearing. Can't see any metallic pieces in the engine oil. I'm hoping that it's the lifter but thinking it might be the piston journal. My one thought is since she shut down sounding fine and as soon as she started it was there I'm hoping it's the cam lifter. So if anyone has some insight, thoughts or tests to try and figure out what it might be I'm all ears. I'm thinking that I'll take the manifold off and look at the lifters but I'm not sure I can definitely tell it that's it. Thoughts...

Chris

[prowlersfish]

Without hearing it its hard to say what it is . Since its was not knocking when shut off I doubt its a bearing . Check for play in the rocker arms , rotate the engine and recheck . if its a stuck lifter or valve you should find some play.

Good luck

[BobCT]

Is it a knocking or more of a rattle? Flex plate on transmission will make a heavy rattling sound when they go bad. Does it make a difference whether it's in or out of gear? I had the exact same issue when my boat was surveyed and it was running on 7 cylinders because of a bad cap. Where is timing set? I'd be surprised if its anything on the lower end, those 454's are pretty bulletproof.

Cooling system good? Meaning you're not partially hydro locked. This would be high on my list because it doesn't sound like you've pushed the engine in a while and it started the "next day".

Bob

[bigrgh]

try taking the belts off one at a time.....i thought i had a rod or crank bearing knock when i unwinterized,even knocked louder when letting off the gas, but ended up being a bearing in my raw water pump. took belts off , ran with no knock.

[Lumpy]

I took the plugs out so I could rotate the engine looking for any play in the rocker arms. When rotating I saw water come out of back starboard spark plug hole. There is not water showing in the oil. My thinking is that a head gasket has blown and the knock I'm hearing is the water going into the cylinder causing pressure, causing the knock. I removed the manifold and all looks ok?? Removing the heads tonight to see. Now on the port valve cover it has what appears to be a milky reseadue at the end of the valve cover above the last cylinder. So could a blown head gasket cause the knocking?

[BobCT]

I was afraid it was some sort of hydrolock

Connecting rods, on the otherwise bulletproof lower end could be the noise you're hearing. Why do you suspect a head gasket? It's usually the cooling system that causes a water intrusion. While you're figuring it out, crank it over with plugs removed to get the water out. You don't want it sitting in there causing more damage. If you're capable of pulling a head, I'm sure you know that already.

Bob

[LandVF36]

I would pressure test the exhaust manifolds before going any further. Since you have them removed, just plug the raw water outlet and then pump in water from a garden house into the inlet. Take a light and look into the exhaust port around the cylinder with the milky valves. You might just see a fine mist water. If not, take a propane torch ans slowly heat the area to see if a crack opens up.
I've had a few fresh water cooled boats over the years about to bring me to tears and then I found it was just an exhaust log.... good luck.

[RWS]

I took the plugs out so I could rotate the engine looking for any play in the rocker arms. When rotating I saw water come out of back starboard spark plug hole. There is not water showing in the oil. My thinking is that a head gasket has blown and the knock I'm hearing is the water going into the cylinder causing pressure, causing the knock. I removed the manifold and all looks ok?? Removing the heads tonight to see. Now on the port valve cover it has what appears to be a milky reseadue at the end of the valve cover above the last cylinder. So could a blown head gasket cause the knocking?

------------------------------------------------------------------------

If you rotated the engine by hand and did it ....

backwards

you could have sucked water into the engine.


Do a compression test with the STARTER MOTOR.

RWS


P.S. Yanmar makes a new 8 cylinder Diesel.....

[prowlersfish]

Stay with the 4 or 6 cly yanmar