Rebuild or Replace

[bjcsc]

Re: Rebuild or Replace

Hey Tony, check this out:

Guess what number cylinder it was?
This happened in my second season with my boat. The explanation given to me was that my intake had a slight leak (but of course I also had the rust you see) and tempered my valve. The piece you see was actually sucked back in and found in #5. I never saw any rust or water on the plugs and I had no indication this was going on. But I also don't know what the PO did either so who knows. I bought a new GM base engine and intake...

 

[FreeBeeTony]

Re: Rebuild or Replace

The plug was not melted........just bent.

Ignition is a thunderbolt 4.

There wasn't any pinging............and the vacum was ~19 and idled fine so I don't think I had a vacum leak.........

This was the same clyinder that was giving me problems from day 1.........then I replaced the heads and intake with the vortecs.

Right now my plan is to give the heads to a machine shop to see if they can be fixed and look for a short block..........

What are the specific causes of detonation? Too much advance a lean condition? The rest of the plugs looked fine...........I will post a few pics of the other plugs.

 

[FreeBeeTony]

Re: Rebuild or Replace

More pics...........now I see the signs of detonation on the pistons.......

The plugs look much cleaner than the plugs from last year..........another sign of detonation?

Now how do I find out why this happened?

 

[wire2]

Re: Rebuild or Replace

I expect this is a carb and not EFI?

Lean condition means you're well under the ideal 14:1 air/fuel ratio for gasoline engines.

I'd verify proper fuel pressure to carb at all rpm's, then take carb to a competent shop for rebuild. Could be low float level, plugged jet, varnish deposit, etc.

There are very small air/fuel LED displays available for under dash but they require an oxygen sensor in the manifold.
Not easy.

 

[Bondo]

Re: Rebuild or Replace

Ayuh,.........

Or it could be as Simple as a Dirty Fuel Filter............

The Fuel System might show Cause,......

I'd start the Hunting at the Fuel Filter,+ move on from There.............

 

[FreeBeeTony]

Re: Rebuild or Replace

All filters are replaced anually and the fuel pump and carb were new.

Is there a way to test for a lean condition?

 

[ziggy]

Re: Rebuild or Replace

hey fbt. do ya have service manual #2? look on page 1A-14. some real good info on detonation........and it's causes.......i know yers is much newer. but..........

 

[JustJason]

Re: Rebuild or Replace

don't bother with detonation... that's water damage right there.

Lean won't tear the carbon off the top of a cylinder but a steam bath sure will.

What happened in your motor is that a slight amount of water was entering the cylinder, and because of the temperatures involved during the compression and power stroke it is almost instantly turned into steam. In turn this tempered the intake valve causing it to shatter.

Steam will strip the carbon off of everything in that cylinder... the piston, the heads, and the spark plug.
Lean will not strip the carbon off a piston, it just won't add as much if any to it. Lean will also not turn a spark plug white, but steam sure will.

Plugs are harder to read than ever. And on top of that, to truely read a plug the right way you need to start with new plugs, run the motor hard, and do what they call a "plug chop"... (killing the ignition system at or near WOT under a load) that's the easy part, the hard part is you have to get the plugs out fast before the heat of the engine cooks off any suspect evidence on the plugs you may be looking for. Its easy on outboards... but can be a bugger on sterndrives.
If water is suspect... you really need to do a plug chop and then look at the plugs the next day to see if rust is starting to set.

 

[FreeBeeTony]

Re: Rebuild or Replace

Don't think it was water intrusion as there was/is no sign of rust on the plugs........

 

[John_S]

Re: Rebuild or Replace

Well, the "Lean" thread is getting very confusing, not knowing if the discussion is on Tony's motor or Quiz of the week. Thought I'd bring this one to the top with some more questions, and for further analysis of this problem by others.

I'm not in the water intrusion or detenation camp. I still can't see how that valve broke without hitting something.


Tony,

Did the broken valves lifter, pushrod, and valve spring appear to be OK?

Did you get a picture with valve cover removed, but before rocker arms loosened? If the adjustment was significantly off (much farther down in lifter) should be able to tell from picture.

Anyway, as you continue teardown, I would be interested in as many pictures as you care to post.

 

[JustJason]

Re: Rebuild or Replace

valve broke because it became "tempered"...
it went hot/cold/hot/cold and became very brittle.....
a combustion chamber running at 800-1000 degrees+ injesting 85 degree water will make anything brittle...
valves are fairly malleable... they have to be because of the extreme heat range (from room temperature to again... 800+ degrees)

 

[John_S]

Re: Rebuild or Replace

I am wondering if some initial damage happened here: http://forums.iboats.com/showthread.php?t=179305

Jason,

As others have said, the combustion chambers do not reflect the results of having water intrusion. I have seen numerous pictures of nice clean heads from water intrusion, but the valves are perfectly fine. Misting water into carbs has been a de-carb solution, used by auto mechanics for many years.

Also, it would have to be extremely brittle to break from just contact with the cyl head. I am not sure if you could get it that brittle by taking it to "red" hot and dropping it in a pail of water. Let alone, with combustion temps much lower than that, and nowheres near the water to do a complete quench, otherwise it would hydrolock.

 

[Windykid]

Re: Rebuild or Replace

I agree with Bondo. Fuelfilter, Tank vents, fuel lines, carb.

 

[JustJason]

Re: Rebuild or Replace

ok john...
then what is the "reason" for that piston and that cylinder head having minimal carbon???
There has to be 1 right???... carbon does not magically dissapear???
I mean... would you at least agree that carbon does not magically dissapear???
or do you think that i can???

would you aslo agree that a "lean" running condition does not remove carbon as well??

 

[Bondo]

Re: Rebuild or Replace

then what is the "reason" for that piston and that cylinder head having minimal carbon???

The only places that Don't have Carbon,.....
Is where there was mechanical Contact with Hard Parts.........

Ayuh,...... This is getting to be a Pain,.....

Running 1 conversation in 2 threads...............

 

[John_S]

Re: Rebuild or Replace

As Bondo states, it was hammered clean from the pieces of the valves. Kinda like very chunky sand blasting If it was water/steam, it would be much more uniform, and you wouldn't have all those dents

 

[Bondo]

Re: Rebuild or Replace

and you wouldn't have all those dents

Ayuh,.....................

 

[mkpj1]

Re: Rebuild or Replace

Totally agree import J.

I used misting water to clean carbed up engines but have switched to ATF. Don't see detonation or water intrusion but thats not to say it didn't happen. both are plausable but based on Free Tony's prior issues I think either he got a set of heads with a poorly seated valve or the guide was off. Could have leaked?? I always set my new heads on the bench and put some gas on the valves. Leave em there for awhile and see if they leak any. They shouldn't!

Anyway that is what wasted the lifter last year. I see it was suggested that he do a leak down which would have shown the poorly seating valve but I don't see that he did. The valve would stick at 3600 RPM, or whatever it was, and it finally broke wasting his engine. That's just my humble opinion?

I would break it down and look at the valve train real close but I really think you got a bad valve job Tony. You really need to take it to someone and have them look it over because I can't tell sh%t for sure from your pics.

In any event, good luck, and get and new one!.

 

[Buttanic]

Re: Rebuild or Replace

I am wondering if some initial damage happened here: http://forums.iboats.com/showthread.php?t=179305

Jason,

As others have said, the combustion chambers do not reflect the results of having water intrusion. I have seen numerous pictures of nice clean heads from water intrusion, but the valves are perfectly fine. Misting water into carbs has been a de-carb solution, used by auto mechanics for many years.

Also, it would have to be extremely brittle to break from just contact with the cyl head. I am not sure if you could get it that brittle by taking it to "red" hot and dropping it in a pail of water. Let alone, with combustion temps much lower than that, and nowheres near the water to do a complete quench, otherwise it would hydrolock.

Reread the other thread and likely enough damage was done to cause a failure over time.

 

[FreeBeeTony]

Re: Rebuild or Replace

I thought I had fixed the original problem when I finally found that bad lifter.

Maybe it wasn't in time and I damaged the valve?

I am replacing with a long block from Rapido............

Thanks for all the intrest............don't really know what else to say at this point...........

Still don't think it's water related though...........

PS......the lack of carbon on that cylinder is defintely from the valve pcs beating the piston to death.