Volvo Penta D6-350 Performance Issue and Black Smoke

[Lax207]

Good day Folks!

Greetings from sunny Indo!
UPDATE: First of al thank you for all the inputs. It has helped so much and one of you was right- a cracked Valve Seat and an Exhaust Valve that gave it the thick black smoke during planning. We have changed all the valve seats, guides and 2 exhaust valves.

Engine runs smoke less, even during planning, however during the first start after the overhaul, the engine was on idle for 15 minutes with this ticking sound. It seems to have skipped a tooth on the timing( we checked the 2 pins on top of the valve cover and flywheel, and one of the alignment holes on the shaft was not precise). Adjusted correctly the timing, and engine purred afterwards, however still a slight ticking sound.

Sadly, after all this positive outcome so far, came the sea trial. Everything performed well, despite still the PORT engine does not accelerate quick enough as STBD (has been the main issue), but reach their top rpm’s without a hint of smoke with all parameters performing very very well. Suddenly the PORT engine creates a thump sound, decelerates, and sounding like something popped loose and giving out a leaked compression sound or like it is running only on 3 cylinders (if only I got it on video, was shooting literally 5 seconds before this happened), So, we shut engine off right away. Up to now we have not opened it up but will do so tomorrow when our mechanic is back.

My question is, during that 15 minutes idle time with the timing gear skipped a tooth, would it be enough to really damage a valve and cause it to break/fall off? Does anyone have similar experiences or any idea what it could be?

NB: We had 3 injectors replaced too and port engine really sounded ‘strong’ after the overhaul, but just the ticking sound that was still there.

Look forward for your thoughts!
Cheers,
Christopher

 

[[2068]]

Unfortunately, this sounds as if you have dropped a valve somewhere along the way.
This could be expensive.
I'm not sure if "one tooth out" would be enough for a piston to hit the valves - more likely something else wasn't put together correctly when the cylinder head went back together.

 

[kashurst]

If the cam was out by one tooth I think you would have to be very unlucky to get the valves hitting the pistons especially at idle speed.
Were you able to turn the engine over by hand before the first start up to make sure there was no physical contacts through several revolutions?
The ticking noise - does the other engine make a similar sound ? - on some engines you can hear the electric fuel injectors operating. Or it could be one of the hydraulic cam followers sticking a bit after the head rebuild (they are hydraulic on a D6 ????)
However the loud thump does not sound good at all.
Fingers crossed its something external like a turbo air pipe blown off or something similar.

 

[Lax207]

If the cam was out by one tooth I think you would have to be very unlucky to get the valves hitting the pistons especially at idle speed.
Were you able to turn the engine over by hand before the first start up to make sure there was no physical contacts through several revolutions?
The ticking noise - does the other engine make a similar sound ? - on some engines you can hear the electric fuel injectors operating. Or it could be one of the hydraulic cam followers sticking a bit after the head rebuild (they are hydraulic on a D6 ????)
However the loud thump does not sound good at all.
Fingers crossed its something external like a turbo air pipe blown off or something similar.

Hi folks!
Found the culprit!
See images below: Seems like the Rocker Arm for Cylinder 5 just broke to pieces. Gave a small wound to the camshaft however not on the spinning side, so hopefully it should not be a problem to use it again, Cylinder 6 rocker arm just dismantled itself to pieces. And so are some of the other rocker arms they don't seem to fit or are mounted a 100%. It is unbelievable how they are simply just mounted on -no locking mechanisms or such, and you can just lift them off with your finger easily. Compression still good, and valves are all still OK.

 

[[2068]]

It's the valve cover that holds the rockers in the right place.
It looks as if not enough care was taken to make sure that everything was in the correct place as the cover went back on.

What does the inner surface of the cover look like?

.

 

[Lax207]

It's the valve cover that holds the rockers in the right place.
It looks as if not enough care was taken to make sure that everything was in the correct place as the cover went back on.

What does the inner surface of the cover look like?

.

That could be it, don't know what else could have caused this. Also, the tiny pins from the cam bearings (15 on each bearing) seems to have fell down the return oil line.

We have 30 pieces missing from the two cam bearings that were destroyed. Any advice on how to get them out? We are hoping that they are down in the oil carter pan as that would be a slight relief. If it is stuck in the oil lines on the block, that can be catastrophic. Thinking of getting a flexible magnet and unscrew the oil dipstick to get access to the pan from there.

 

[volvopaul]

Hi folks!
Found the culprit!
See images below: Seems like the Rocker Arm for Cylinder 5 just broke to pieces. Gave a small wound to the camshaft however not on the spinning side, so hopefully it should not be a problem to use it again, Cylinder 6 rocker arm just dismantled itself to pieces. And so are some of the other rocker arms they don't seem to fit or are mounted a 100%. It is unbelievable how they are simply just mounted on -no locking mechanisms or such, and you can just lift them off with your finger easily. Compression still good, and valves are all still OK.
View attachment 66680View attachment 66681View attachment 66682View attachment 66683

I'd be binning the whole lot , how do you know the valves are still ok, have you taken the head off?

That's serious damage looking at how it's all fell apart, I take it you didn't take the engine out the boat to do the previous repairs? Is this boat in the U.K.

 

[Lax207]

I'd be binning the whole lot , how do you know the valves are still ok, have you taken the head off?

That's serious damage looking at how it's all fell apart, I take it you didn't take the engine out the boat to do the previous repairs? Is this boat in the U.K.

The head was just assembled before this incident happen, and we did check the valves from the top if there was any resistance in play to indicate it being bent or broken. All was attached and worked fine, fingers crossed. We rotated the flywheel to check compression and all 6 cylinder seemed to be okay. We have ordered 12 new rockers and arms for the exhaust side and will begin with that.

Now as for the bearing pins a total of 60 must have dropped down to the pan/and or reinforcement plate under the crankshaft (see picture). Using a flexible magnet we unscrew the oil dipstik bolt on the bottom and managed to retrieve 21 of the bearing pins below. However no more success, even when we have gone around the pan and also going rom the top return oil channels, no more success. Our biggest suspicion is that they are stuck/gathered on the bottom of the reinforcement plate as its U shaped structure makes the pins easily collect on the lowest point of the part.

We have flushed with diesel a few times to try and make them 'slip' down to the oil pan and will also try to flush with engine oil as a last attempt. To lift up the engine and opening the oil pan is a huge job here and it also means having to move the starboard engine.

Have anyone had any similar experiences? In my understanding is that once the bearing pins fall down to the oil pan, it should stay there, or at least hopefully...

 

[aquatom]

If you really can’t get the sump off then attach a few large magnets to the bottom of the sump to hopefully collect them then after running it’s been run remove the dipstick tube again and the magnets and try to get them out.
Good luck.....

 

[Lax207]

Good day Gents!
Our Cranchi 41 is finally up and running with fire on all cylinders. Port engine is much stronger than before. We changed the rockers and the cam and the ticking noise has disappeared. She purrs very quiet and accelerates like a horse kick on the back...Very very happy with the results so far, and lets just hope it keeps that way. Next issue is on our D3, but I will make a separate post for that.
In the mean time, please enjoy a Before and After vid on our sea trial of her and you can hear and see the difference. Thank you again very much for all your supports and exchange of ideas. Highly appreciated!

Before Video:
https://youtu.be/GyPnGtsqrEk

After Video:
https://youtu.be/wUWEdsiQkeg