Penta 2002 reduction valve function?

[Contest1]

Still burning oil after my rebuild last year.
Engine starts on the button and runs smoothly.
Just the oil, usein about a pint ever couple of hours.
It was much better before the rebuild as I do not rember an abnormal usage.
Anyway I have bought new valve stem seals, not yet fitted, even though there were definatly none removed during the strip down.
I have been searching for likely culprits to explain this issue and a few web sites mention the reduction valve. I did not open it during the rebuild so am wondering if this could be part of the problem.
Other issues that came up were the valve stem seals and the pressure equalising vent that can be blocked if the head gasket is misaligned on assembly.
One odd thing is that if the engine has not run for a week or longer the smoke takes a good few minutes to appear. This leads me to think it could be a build of oil under the rocker cover. Another sympton is I feel it takes an unusualy long time for the oil levle to stabalise on the dip stick. I,m no mechanic so maybe I,m grasping at straws.
Running at 1700 revs the smoke is minimal but really goes to cloud formation if I have to put on a spurt for any reason.
All advise welcome.

 

[Vegable]

Don't know anything about reduction valves I'm afraid. From your description it seems that oil is getting into the combustion chamber. So it either comes down from the top - valve guides/seals, along from the middle - wrong or incorrectly fitted head gasket, or up from below - are the piston rings correctly fitted? ie the gaps in the piston rings aren't in alignment but deliberately offset? And for that matter the correct size of piston rings.
How stiff is the compression when you try to turn the engine over by hand?
This is about the limit of my expertise now! Good luck.
Mike

 

[Seamechanic]

Hi,

the simple question for the beginning ;-)
Did you check the correct orientation of the valve cover gasket ? If it's turned (front end to the rear) the crankcase ventilation into the air inlet is blocked. Pressure builds up and may force oil to bypass the (maybe already weak) valve stem seals....

Frank

 

[VicS]

The reduction valve controls the lubricating oil pressure.

There are some figures relating to the spring length in the Tech data section of the w'shop manual

 

[Contest1]

Thanks guys.
Going to make a start later so fingers crossed its one of the simpler solutions.
Presumably if the reduction valve controls oil pressure it likely ok but will check it now I understand its function.
Rocker cover gasket is coming off anyway so can start there and work from there.
According to the web the valves can drop on to the piston even at TDC and make getting the collets back on impossible unless I pressurise the cylinder void with oil or air. Anyone managed this without the oil or air.

 

[Contest1]

Tried a few of the suggestions today. Changed the oil filter just in case!!
Rocker cover gasket ok. Managed to push a fairly stiff electric wire into the vent far enough to have passed throught the head and probably into the sump so no blockage or head gasket misaligned.
just in case it was over pressure under the rocker cover I pulled the compression leaver out beyond the seal. No difference to the smoke at the exhaust and no apparent escape of pressure or oil.
By the description of the reduction valve function I can,t imagine it could cause the oil burning.
Looks like its the stem seals next!
Anyone know of a handy way to prevent the problem of the valve dropping so far as to make it impossible to compress the spring enough to get the collets in place.

 

[earlybird]

If you're thinking of removing the valve collets without removing the head,I don't see it as a good idea.
BTW, I'm not sold on the theory that your oil is going down the valve stems. Diesels don't challenge the seals in the same way as petrol engines.

 

[Contest1]

Interesting thought! If the compression is good enough to start on the button and there is no oil under the engine or in the exhaust cooling water were could I be losing it.
Could it enter the cylinders via the piston rings somehow?
I did check the new ring gaps as per the specifications but did replace the oil sweeper ring I broke with a OEM.

 

[<152587>]

What did you do ref the cylinder bores? If you just replaced the rings I would expect the symptoms you are experiencing. Although the cylinder bores were to spec with little or no wear, a hard surface is created on the walls during use. You should have glaze busted the cylinders to relieve this hard surface providing a softer surface for the rings to bed to.

 

[Contest1]

Spent a few hours deglazing with a close fitting cylinder and very fine emery. Circular only no lateral. No glazing symptons or noticable oil loss before rebuild!

 

[MonniotC]

You say the rocker cover gasket is on the right way round, but is there a right way and a wrong way to put the cover itself on - the wrong way blocking the vent?

 

[<152587>]

Spent a few hours deglazing with a close fitting cylinder and very fine emery. Circular only no lateral. No glazing symptons or noticable oil loss before rebuild!

Then there is your problem. Consider when an engine is running at say, 1500 rpm the piston is traversing the cylinder 3000 times, so in an hour that equates to 180,000. This has the effect of polishing the rings and the bore to a "glass" finish and because of the particular sharpness of the ring edges ( Cut your finger with an edge of cast iron you will find out how sharp) will effectively hone themselves to fit on a new or rebored engine.

This "glass" finish is also extremely hard, speak to anyone who has machined cast iron, the only way is slow speed and razor sharp tools.

It is doubtful, in my opinion, that 1. The hard surface may not have been sufficiently broached. 2. By using a cylinder wrapped in emery you cannot guarantee the consistent pressure around the circumference of the cylinder, don't forget that the first rebore is 0.010" so you could have now a cylinder bore looking like a bi-hexagon by a few thousands of an inch.

Your best bet is to run it fairly hard in the hope of rings bedding although this may take several hours, if problem still persists then a further strip and rebore.

 

[Contest1]

Then there is your problem. Consider when an engine is running at say, 1500 rpm the piston is traversing the cylinder 3000 times, so in an hour that equates to 180,000. This has the effect of polishing the rings and the bore to a "glass" finish and because of the particular sharpness of the ring edges ( Cut your finger with an edge of cast iron you will find out how sharp) will effectively hone themselves to fit on a new or rebored engine.

This "glass" finish is also extremely hard, speak to anyone who has machined cast iron, the only way is slow speed and razor sharp tools.

It is doubtful, in my opinion, that 1. The hard surface may not have been sufficiently broached. 2. By using a cylinder wrapped in emery you cannot guarantee the consistent pressure around the circumference of the cylinder, don't forget that the first rebore is 0.010" so you could have now a cylinder bore looking like a bi-hexagon by a few thousands of an inch.

Your best bet is to run it fairly hard in the hope of rings bedding although this may take several hours, if problem still persists then a further strip and rebore.

Just replacing the valve stem seals next. Looks like I can get enough spring compression with the cylinder at TDC holding the valves from droping more than about 2mm.
Rocker cover only goes one way so I have eliminated that and over pressure from my list of possible culprits.
Ill certainly try you tip on a prolonged Italian tuneup next trip out but if it presists I will just top up the oil as necessary! After all it is a sail boat&#55357;&#56832;

 

[Contest1]

Just back on board after summer break in Ireland.
Engine still Smokey and burning oil but it appears to be improving following some extended running last June.
I was turning her over by hand and forgot to put the release lever back to compression.
Engine started and ran smothly but the smoke was embarrasing. Reset the lever and smoke levle back to what passes for normal. Could this be a clue to the excesive oil consumption. Maybe something not quite right in the compression release department?
Going to check out the reduction valve when it gets a into the dark short days. Enjoying the shorts and tea shirt sailing too much just now.&#55357;&#56842;