Kelvin exhaust valves

[richardf]

I have a Kelvin P4 of 1960 vintage which I have had for about 2 years. Last winter the heads came off and were decoked. The engine ran much better after this and the popping noise it had been making disappeared. Since then it has been run for only about 100 hours, but the exhaust valves are all coked up and sticking (a piston has been clattering one of them on a regular basis!).

I am at a bit of a loss to know why this should be; some more facts below.

I fitted a silencer soon after I got it, but this was one you can see daylight through and should not increase back pressure

The engine has been running a lot cooler since it's decoke.

It's always been smoky and blows out big lumps of soot- could it be that the exhaust is blocking up as it's not as hot as it was? I have a feeling that the lumps of soot have decreased, maybe they are building up somewhere and blocking up the exhaust, hence causing back pressure.

I can restrict the water flow around the engine to force it to get hotter, currently the water is only warm when it exits the head.

Does anyone have any other ideas or suggestions?

Thanks

[RLWP]

I wonder if your valve guides are shot and are allowing oil down to burn on the backs of your valves

 

Richard

[Timleech]

I wonder if your valve guides are shot and are allowing oil down to burn on the backs of your valves

 

Richard

 

That sounds likely.

 

Later versions of the Kelvin T valves have a circlip in a groove between top of guide and collet, my guess is that it's there to reduce the amount of oil running down the valve stem.

 

Tim

[David]

hi

This subject was covered over several issues of the Kelvin Register and Vintage Marine Engine members mag a couple or more years ago, I contributed to it also because after investigating a wheezing exhaust note from my engine when I first bought it, coupled with large lumps of hard soot blowing out of the exhaust and a occasional missed beat (maybe your popping noise) when a large puff of smoke appeared then then the engine would run clean.

To cut short when dismantled the exhaust ports were almost blocked with carbon, this had also been the case with other contributors to the dicussion. My engine had slightly oval valve stems allowing more oil to get down the guide, the wick drippers I also discovered were dripping to fast hence more oil collecting arround the valve stems (I assumed the dripping rate was OK when I first had the engine)also the engine mostly ran cold in fact the cylinder No3 head which ran the coldest had a small hole through the carbon smaller than my little finger, plus the injector nozzels were "drippy" and not the correct angle spray so incomplete combustion. All ideal for heavy build up of carbon, also back when the Kelvin was designed it was normal for engines to be de-coked annually, I certainly remember doing it on my first m/bikes and cars. Attending to all of the above we now have not de-coked for 4 years, I had the exhaust manifold of 2 years ago and had only a few mil's of carbon in the port.

david

[richardf]

Is it possible that the head decoke and general clean up may have removed some carbon in the valve guides that was absorbing oil seeping down from above.

If it is a guide problem, what are my options? Not even sure if there are guides that can be renewed or is it a case of getting it drilled out and new guides installed?

 

hi

This subject was covered over several issues of the Kelvin Register and Vintage Marine Engine members mag a couple or more years ago, I contributed to it also because after investigating a wheezing exhaust note from my engine when I first bought it, coupled with large lumps of hard soot blowing out of the exhaust and a occasional missed beat (maybe your popping noise) when a large puff of smoke appeared then then the engine would run clean.

To cut short when dismantled the exhaust ports were almost blocked with carbon, this had also been the case with other contributors to the dicussion. My engine had slightly oval valve stems allowing more oil to get down the guide, the wick drippers I also discovered were dripping to fast hence more oil collecting arround the valve stems (I assumed the dripping rate was OK when I first had the engine)also the engine mostly ran cold in fact the cylinder No3 head which ran the coldest had a small hole through the carbon smaller than my little finger, plus the injector nozzels were "drippy" and not the correct angle spray so incomplete combustion. All ideal for heavy build up of carbon, also back when the Kelvin was designed it was normal for engines to be de-coked annually, I certainly remember doing it on my first m/bikes and cars. Attending to all of the above we now have not de-coked for 4 years, I had the exhaust manifold of 2 years ago and had only a few mil's of carbon in the port.

david

 

Sorry, just missed your post, what model of Kelvin was this?

[David]

Is it possible that the head decoke and general clean up may have removed some carbon in the valve guides that was absorbing oil seeping down from above.

If it is a guide problem, what are my options? Not even sure if there are guides that can be renewed or is it a case of getting it drilled out and new guides installed?

 

 

 

Sorry, just missed your post, what model of Kelvin was this?

 

Sorry about delay in reply, I am refering to my J I don't know about the P but J guides are replacable, my guides were OK some of the valve stems had worn though.

david

[richardf]

I'm told that all 4 valves are coked and on reflection, the problem started after about 30 hours of running. I would have thought that worn valve guides were more likely to have shown uneven wear across the 4 cylinders. The head was professionally rebuilt and I assume that valve guides were checked as part of this process, but I will ask.

Could it be related to the injectors (the crack off pressure was set much lower than normal, but that was how they were set before reconditioning)

The engine is running much cooler and we were icebreaking for a lot of the 30 hours, could this be significant?

Has anyone tried any of that stuff you put into the fuel to clean injectors and valves? I did put Fuel Set in the tank a while ago?

The engine is very smoky ( most P4s are the same), perhaps I have soot building up somewhere that is building up a back pressure, certainly the spigot on the roof shows considerable soot build up.

Edited June 12, 2011 by richardf

[richardf]

I'm confused, my mechanic has got the engine running smoothly again without the need to remove heads and he reckons it was due to insufficient oil going down the valve guides and the valves coking up in their guides. This seems to contradict the wisdom that was offered earlier about too much oil burning onto the top of the valves through worn valve guides!

Can someone explain - is there supposed to be oil running down the valve stems, there seems to be no seals at the top or anything and the oil supply would be a pretty hit and miss operation.

Does my theory about running hotter in future offer any solution - they have coked up so quickly!

Any advice much appreciated

[cereal tiller]

i am not familiar with kelvin's and do not know whether valve guide seals are necessary or not.

if the engine has had new valves/guides then a suitable clearance would allow just enough oil to lubricate the valve stems,maybe your new guides/valves are running a bit tight.

 

rapid sooting is indicative of incomplete combustion.

 

what colour smoke does the engine emit when cold,does it change once the machine is up to temperature?

 

it may be that the combustion area is too cold?

 

what is your operating temperature?

 

i may be worth considering an additive to raise the cetane rating,i have used a diesel/parraffin mix on elderly engines successfully.

 

does the engine start easily?

 

are the injectors calibrated correctly?

which sump lubricant are you using?

 

lots of questions,but they may lead to a sensible solution.

[RLWP]

Trouble is, a Kelvin can take over half an hour to get up to running temperature

 

Rapid 'sooting' is also an indication of oil burning off on the back of the valves from stem/guide wear. However, I haven't taken the engine apart

 

Richard

[richardf]

i am not familiar with kelvin's and do not know whether valve guide seals are necessary or not.

if the engine has had new valves/guides then a suitable clearance would allow just enough oil to lubricate the valve stems,maybe your new guides/valves are running a bit tight.

 

rapid sooting is indicative of incomplete combustion.

 

what colour smoke does the engine emit when cold,does it change once the machine is up to temperature?

 

it may be that the combustion area is too cold?

 

what is your operating temperature?

 

i may be worth considering an additive to raise the cetane rating,i have used a diesel/parraffin mix on elderly engines successfully.

 

does the engine start easily?

 

are the injectors calibrated correctly?

which sump lubricant are you using?

 

lots of questions,but they may lead to a sensible solution.

 

Thanks for your interest,

P4s are notoriously smoky and mine is no different - it is a grey smoke (oil smoke probably)

 

Since being reconditioned, the temperature of the water that exits the heads is MUCH cooler than it was - I have a valve that manually adjusts the amount that runs through the engine / round the bypass - I can open this to put more down the bypass. Temperature measurement is a bit hit and miss - I have one of those copper tubes wired to the water pipe by the head - no idea how it actually works, but there is no power supply to it, simply reads off a gauge that is attached by a cable - unless the engine is running really hard on a long pound, or has just been switched off, the gauge hardly moves onto the scale. Before the heads were done, it would quite often be in the green zone on the gauge. Water pipes feel luke warm, so probably nowhere near hot enough.

 

I have added Fuel Set to the engine - don't know what that does to the cetane rating.

 

Engine starts first time, every time, without fail. Injectors were reconditioned when the heads were done. The crack off pressure was set substantially lower than the 180atms recommended as that is what they were set to before and the engine ran really rough at 180atms.

 

Lubricant is Morris Oil - thnk it is a straight 30 - whatever it is recommended to run on.

 

Hope there is a clue there somewhere!

[LEO]

Thanks for your interest,

 

Temperature measurement is a bit hit and miss - I have one of those copper tubes wired to the water pipe by the head - no idea how it actually works, but there is no power supply to it, simply reads off a gauge that is attached by a cable -

 

Hi,

 

A better method of checking the water temperature (assuming the pipe work is copper) wold be to fit a 'pipe thermometer (cheap ones are available from B&Q) and fit this to the pipe with the spring attached.

 

I use them on the 15mm flow and return pipes to tke Kabola boiler

 

Hope that helps.

 

Leo

[richardf]

Hi,

 

A better method of checking the water temperature (assuming the pipe work is copper) wold be to fit a 'pipe thermometer (cheap ones are available from B&Q) and fit this to the pipe with the spring attached.

 

I use them on the 15mm flow and return pipes to tke Kabola boiler

 

Hope that helps.

 

Leo

 

What a great idea! I'll do that - cheers

[Timleech]

It does sound to me likely that you have too much oil passing the guides. Too much will cause coking, but too little can also allow carbon to build up on the stem.

Some engines seem much more tolerant of guide wear than others.

Your thermometer sounds like an ordinary mechanical one with a capillary tube - a bulb of some fluid or other (used to be ether in at least some examples, I gather that they use nitrogen now) connected via a very fine tube to a Bourdon gauge. The tube is very easily damaged, but if it has been your gauge is likely not to work at all. They can be repaired, at substantial expense.

 

Tim

 

Edit to add - it certainly won't help things if it's running too cold.

Edited June 16, 2011 by Timleech

[richardf]

It does sound to me likely that you have too much oil passing the guides. Too much will cause coking, but too little can also allow carbon to build up on the stem.

Some engines seem much more tolerant of guide wear than others.

Your thermometer sounds like an ordinary mechanical one with a capillary tube - a bulb of some fluid or other (used to be ether in at least some examples, I gather that they use nitrogen now) connected via a very fine tube to a Bourdon gauge. The tube is very easily damaged, but if it has been your gauge is likely not to work at all. They can be repaired, at substantial expense.

 

Tim

 

Edit to add - it certainly won't help things if it's running too cold.

 

Thanks Tim,

 

The short term advice from my mechanic was to use an oil can to soak the top of the valve stems in the hope of dissolving some of the carbon (that is what he has done to 'fix' it) - any thoughts on that? What about engine additives that are supposed to clean injectors/valves etc. Snake oil? Just a lift in the cetane rating of the fuel presumably?

[RLWP]

When your mechanic measured the diameter of the valve stems and the bores of the guides, what did he find?

 

Richard

[cereal tiller]

sounds like the engine is,indeed, overcooling.you could always fit an inline thermostat to regulate the flow between engine and by-pass.

the mercedes O.M.636 marine engine has one as standard .

 

when the injector crack pressures were reduced,was the timing adjusted?

 

as i mentioned before,i have no knowledge of kelvins,but i did used to look after a deucshe

(cant remember how to spell german)

industries hot bulb 2 stroke engine installed in a dutch barge,and accurate temperature control was the key to making it run clean.

[paulcatchpole]

sounds like the engine is,indeed, overcooling.

 

Apologies in advance if this question is completely inane, 'cause this ain't my arena, as it were...

 

Is this what's known as wet-stacking then?

 

PC

[cereal tiller]

it is possibly best described as the opposite of "hot soak"

 

i would have assumed"wet stacking"is something that trawlermen do when returning to their home port.

 

apologies for my inane response

[paulcatchpole]

it is possibly best described as the opposite of "hot soak"

 

i would have assumed"wet stacking"is something that trawlermen do when returning to their home port.

 

apologies for my inane response

 

Hee hee...

 

I thought wet stacking came from under-loaded and under-temp diesels.

 

But now that I've looked up a definition, it appears to be the same as slobber, like Mr Fincher's BMC suffers from. Unburned fuel + a bit of oil ending up in the exhaust.

 

Sorry, complete distraction.

 

PC