JKE

Intake or Exhaust...does not matter. If so, do you know why?

Owner abuse or freak thing?

I am curious for some reason

Thanks,

John

DieselDaze

Ive got a piston sitting right here in front of me (that I now use as a pen holder) that came out of a Cummins N14.
One of the valves dropped in that engine leaving some real nice marks in the top of the piston.
This was a stock N14. I did not hear the reason for the dropped valve but the mechanics at the Cummins shop made it sound like it was just "one of those things" that happen.

Rich.

Mexstan

Never seen an intake valve drop but have seen the results of many exhaust valve heads breaking off on gassers. Makes a real mess quickly.
Here is story that is not on topic but is the result of a dropped valve.
Too many years ago to remember I was involved with general aviation in South Africa. One of our customers was a crop dusting company. We received a call one day that one of their aircraft had made an emergency landing due to severe mechanical problems with the engine. The decision was made for me and another guy to drive up (a few hundred miles) with a replacement engine. I have done this kind of thing many times. Only one small problem this time. He had landed in on of the big game reserves there.
We finally found the plane, did some checks and found that it had swallowed a valve. Easy to figure out because one of the spark plugs was beaten to pieces and that cylinder had zero compression.
Changing the engine was no big deal. Only thing different was that there were two huge rhinos grazing close by. We parked the truck with the aircraft between us, left the doors open and facing away from them. I have been chased by a rhino in the past and have first hand knowledge of how fast they can move. One guy always had on eye on the rhinos because they were so close. Talk about an incentive for a fast engine change. They took off once we fired up the engine to test it.
This valve became a common problem on that model of engine and the manufacture eventualy went to a larger diameter valve stem which ended the problem.
OK, end of story. Back to the thread.

Shovelhead

This was a TSB subject from Mother Cummins, that discussed the "Long Idle" times in cooler weather, and began the High Idle Controler discussions.

When idleing for long periods of time in cool temps, the engine can't get up to proper temperature causing unburt fuel to be deposited on the valve stems and create "varnish", causing the valves to hang, and the engine damage related to Piston smacking hung open valve.

TXBobcat

[quote author=Mexstan link=board=8;threadid=20133;start=0#msg189174 date=1064508293]
One of our customers was a crop dusting company. We received a call one day that one of their aircraft had made an emergency landing due to severe mechanical problems with the engine.
[/quote]

Mexstan,

Just curious, did the plane happen to be an Air Tractor, yellow and blue maybe? I was just wondering because both my in-laws work for Air Tractor, assembling crop dusters right here in Texas. Don't they have Pratt and Whitney engines in them?

Mexstan

This was a Piper Pawnee with a Lycoming engine. It was new at that time. The P&W engines did not have this kind of problems. Never was involved with Air Tractor but had a lot to do with Ag-Cats and used to go to the dealer in Haiti, Mo often. Been to the factory in NY to pick up a bunch of new ones also.

JKE

I have the valve prints in front of me, well for the 12 v and 24v 5.9 B's and figure there is about no way one will fail even under serious horsepower.

Heavy duty, just like the rods ;D

we supply cummins 100%...I think

We used to make sodium filled ultra lites for ford. 1 guy had several valve failures in an old mustang and he could not understand why since he only drove about 100 miles per year and never drove hard. We researched his habbits and found that he would let the car Idle in the garage for about 10 minutes then shut it down. Did this about once per month or so : ....Folks, this causes condensation in the engine and was causing corrosion on the valve stem. Well, sodium filled vavles have hollow stems with thin walls. This + a little corrosion = snap! This was way back....

We rebuilt his engine (lots of new parts) and discussed the proper way of treating the engine and it never happened again.

On the cummins, you do not have to worry about that! ;D

JKE

So, lesson is; proper temp is very important...not just for oil...also the "varnish" could and would cover the valve seat and cause improper sealing. this will then not allow enough heat dissipation in that area through the seat insert in the head. This is what we refer to as a burnt seat. The high temp and exhaust gasses will actually cut/burn a groove across the valve seat there...not good.

If you care, 76% of valve heat content is dissipated through the seat insert.

The N14 failure could have been excessive seating velocity (high RPM). This will cause the tip end of the valve to snap off at the keeper.

sulfidation failure from sulfur content in diesel fuel is not good either. This is why I posted the info when they were discussing using off-road fuel. : Live and learn.

John

Monty

One of the worst ones I can think of was in a schoolbus. 12v. #3 seized, valve kissed the piston, the driver kept driving, eventually broke the crank gear right around the shaft and quite a few bent valves. Block was toast, could only reuse the head with new valves etc.

DieselDaze

[quote author=JKE link=board=8;threadid=20133;start=0#msg189275 date=1064523037]

...
The N14 failure could have been excessive seating velocity (high RPM). This will cause the tip end of the valve to snap off at the keeper.
...
John
[/quote]

Could have been. I dont know, but it sure makes a nice pen holder now.

Rich

JKE

See, there is a positive side to everything ;D

School bus driver :. The loss of power (and increase in racket) should have been a clue to stop ASAP!

1 other thing I have is examples of valves from engines that use fuel additives, lubrication additives and fuel stability additives...not good again.

I would NEVER run any additive in my truck. I will just have to replace whatever it is that the additive is supposed to be helping......Sulfur and additive is long term though (for the men holding onto their trucks)....

Monty

Can you give us an idea of what kind of wear you have seen when running fuel additives?

JKE

not wear, build up and some corrosion. The valve fillet area will eventualy be completely covered in deposits. You will no longer be able to see (if removed) the fillet radius, drive diameter or fillet angles and possibly the 2nd &/or 3rd seat (intakes). Very ugly, very heavy, and very restrictive to air flow. Baked on Caked on.

Horsepowerrobbingfriction... a joke we have.....with the Shortround twist.

Tartarus

So we're doggoned if we do (valve fillets), and doggoned if we don't (VP44's). :

Don't suppose you know of any fuel -lubrication- additives that don't leave deposits over the long term? Would water injection clean them off?

2manydogs

How does an intake valve in a Diesel get deposits on it from a fuel additive? The only thing they do is let air in. The fuel never sees the inside of the air intake system. Now, maybe, bad guide seals letting a little oil down on them but I don't get the additive thing. Please explain. Jim ???