Turned the key and..KAPLOYEE, KABOOM...

[Mark Maulden]

This also happened last spring. Volvo MD17c that I rebuilt 5yrs ago.. Smoke out the middle air intake. Removed the middle rocker cover and found a bent pushrod..Removed the middle head and machinist stated it could have been a valve hanging up. Reinstalled and ran all last summer up to the Broughtons and back for two months. Got back first week of last August and parked the boat to do other things. Started it up in Jan and ran fine. Started it up a week ago and KAPLOYEE/KABOOM...Ok, based on previous experience, removed the middle rocker cover and bent pushrod...Replacd the pushrod and turned engine over by hand to adjust and bent another one...Another pushrod and everything adjusted and engine ran fine...OK, so off came the head today and going to a head shop tomorrow. I put a mirror over the jacket and shined a flashlight to the tappet. Broken!! Appears that the upper rim is broken and some metallic "stuff" off to the side...I did have two known straight pushrods and rotated engine by hand to verify they both moved "same amount" which did....tomorrow is machine shop and try to extract the tappet with a magnet...i may have to move the jacket up to see if the tappet guide is scored....Hmm..so did a slow moving valve cause the tappet issue? Or did the tappet issue cause the pushrod problem? We'll start by seeing what the machinist says..Fortunately, I have a lot of spare parts from an engine given to me..one pushrod is $92...only two left. I'm pretty good with engines but this is baffling....

 

[Charles Erwin]

Rockers too?

 

[Mark Maulden]

Rockers are well. They move on the arm under their own weight. Stem caps look good also

 

[AWalker]

My guess is sticky valves, causes bent push rods and broken tappets.

 

[Charles Erwin]

Rocker stud backing out can cause this. Spring bind is possible too. No marks on the piston top surface probably rules out interference. Anyway since you intend to remove the head all will be clear soon.

Lifter damage means debris in the crankcase and new lifter w/ old cam presents additional risk. So ask questions of your machinist

Charles

 

[Bill Roosa]

I'd say an under oiling problem on the valve guides. Once it gets going and oil is flowing there is enough to keep the valve stem from sticking. Leave it for a good long while or run it for only a short time and don't get it good and hot (and oiled) then turn it off and the valve stem sticks in the guide.
Check the oil passages ways for obstruction and the guide/stem for galling.
if everything checks out I'm thinking that some sort of shutdown procedure like letting it idle till it cools down some or advanced oil treatment (STP oil treatment?) is in order

 

[Mark Maulden]

Update: got the head back and the valve was firmly stuck due to heavy carbon buildup. This is the second time (year) with the same cylinder. Tomorrow, I'll look at the manifold/other heads and see if there are any differences to the other two cylinders. Machinist said carbon is either fuel or oil. Injectors did come out pretty loaded with carbon and they always have. Only ~100 hrs on injector rebuild. So, he is thinking rings. Said to think about adding Lucas oil stabilizer as the older engines are not doing well with newer oils. This engine is 60s technology and rated for CD oil that can no longer be bought..Come to think about it, I started using Delo 400 two yrs ago. Previously, I was using Delo 100...

 

[Mark Maulden]

Injector for that cylinder is scored. After a complete rebuild last spring! I always seem to have injector issues. Rebuild it and replacing oil with Delo 100 40wt..Admiral and were discussing all this along with past history and we've decided we're gonna repower this fall.

 

[Terry Cox]

Hi Mark, bummer. Interfers with sailing big time. Sounds as though she is running fine at the moment. Do you have a new engine brand in mind?

 

[Mark Maulden]

Probly a Beta 38 with their saildrive..was considering a 35 but I would have to use my current volvo saildrive. And when the saildrive craps out, it would have to be another volvo. So, I'm electing to just replace the whole pkg. The 35 maxes out at 2500 rpm and the 38 maxes out at 3600. These issues stem from the fact that the gear ratios are different between the two saildrives. Emerald Marine in Anacortes would do it and they will let me do all the volvo teardown, battery removal etc in prep for removal. He said I could help in the whole process which save a couple boat bucks in labor..There some things to work out also suchas the oilchange pump is on top and with a pull stroke, it might hit the cockpit sole. Dipstick is on top also..so I'm still in the middle of figuring it out.

 

[Dennis Kitchen]

Mark,
Take a look at your cam lobes, particularly on the cylinder that keeps failing. If your exhaust valve lobe is excessively worn it will choke the cyl. and cause excessive heat and back pressure which will cause valve coking.
Dennis

 

[Mark Maulden]

The only view of the cam lobes would be through the tappet hole with (head and cylinder removed) or removal of the cam. View through the hole isn't going to tell ya much and cam removal says engine removal and I'm not going to go that deep into a 37 yr old engine. The valves adjust out fine and they all adjust the same looking at the adjustment screws. Observing the rocker actions, there does not appear to be any flat spots.

 

[Mark Maulden]

So, things are back together and engine runs great! Have not sea trialed though but have pulled the dock. next few weeks are rafting through the Grand Canyon and afterwards, will change oil back to Delo 100 40 wt since 30 wt is no longer available. I'm still going to repower as this could be a multi year experiment and I have other and things to do than deal with engine issues every spring or wondering "if and or when"..