Valve Guide lubrication (rate) 5

[477stephen]

Hi there
Has anyone else noticed the decline of the "internet"?

Cant seem to find any information on it these days

I have an older engine Single cylinder British bike. I have a high rate of valve guide wear. Due to inadequate oil supply ( 25cc at 3000 rpm ON a good day ) so I needed to know what would be an acceptable oil flow the only reference I can find says about "Normal values lie in a range of from 0.007 to 0.1 cm 3 /10 h" ( 3 x 10^-6 cm~3/secomd?)
Does anyone have any information on Valve guide lubrication rates?

I really appreciate any help you can provide.

Stephen

 

[BrianPetersen]

"25cc at 3000 rpm" is not a flow rate. 25cc over what period of time? I'm not going to make the ASSumption that it's over the same period of time as the crank makes 3000 revolutions. So, there's that ...

What's the bike, and where are you located? Many of the older British bikes retain a decent enthusiast following, and surely someone in those enthusiast groups would know who the specialist is who deals with those engines and knows how to make them last. For example, here in Canada, two places to start are the Canadian Vintage Motorcycle Group

http://www.cvmg.ca

and the Vintage Roadracing Association

http://www.vrra.ca

N.B. Pushrod rocker-arm OHV valvetrains usually don't need much lubrication to the top end, just a tiny trickle to stop things running dry. Overhead-cam valvetrains need to be pretty near flooded to maintain hydrodynamic conditions at the cam followers and, probably, cam journals.

 

[477stephen]

Hi there
Thanks for the reply

Your ASSumption was correct. I thought it was obvious, but you know what thought , thought.

The bike is a Royal Enfield Bullet and I'm afraid I am one of those " specialists" Hence the original question How much flow?

I have the "bronze bearing Design manual 5th edition 1979" as well as the machineries handbook both give Q for full and mixed flow for a rotating sleeve bearing. Now I know these things ( Pushrod OVH flat tappet) don't need much ( and it isn't getting much ) What I need is either Q ( cc per min kg/s etc) for a "reciprocating plane bearing" ( boundary and mixed condition) i.e a min Q to ward off boundary condition ( or the best it can do )

hope that makes sense

Thank you for your input

Kind Regards

Stephen

 

[BrianPetersen]

OK. I have no specific knowledge of that particular engine. All my stuff (that's running) is Japanese DOHC 4-valve-per-cylinder liquid-cooled and with shim-under-bucket valve actuation that is geometrically impossible to side-load the valve stems. So, generalities ...

Bear in mind that in a normal (nowadays) application, the valve stem passes through the valve stem seal whose job it is to keep lubrication OUT of the valve guide, so that the engine isn't an oil-burner. Only the tiniest trace of lubrication remains on the portion of the valve stem that passes in and out of the valve stem seal, and that is enough to get the job done.

0.1 cm3 in 10 hours of running would be 1 cm3 in 100 hours which is in the vicinity of a normal oil change interval on a modern engine, and that is presumably per valve, so in one of my engines that would represent 16 cc per oil change interval ... negligible, and that's the upper limit of the consumption range that you found. I'd say that's plausible.

Stuff that can cause high valve guide wear ... doubt if this is a complete list.

#1 wrong material for the valve guides. "Bronze" covers a lot of ground. Did you buy these from a common supplier? A good, reputable supplier? What guides did you install?
#2 wrong clearances at original assembly. Either too tight or too loose will cause problems.
#3 misalignment. Are you replacing the guides together with installing new valve seats and machining the seats in-situ with Sunnen valve guide and seat machining equipment? Or some other equivalent good equipment? Or are you winging it, and if so, how are you ensuring proper alignment and tolerances? Valves new - or bent?
#4 excessive side loading of the valve stem due to improper rocker arm geometry. Is the rocker arm pushing down dead-nuts in the middle of the valve stem and is the travel of the tip of the valve covering the middle of the arc of the rocker arm? Is the tip of the valve properly machined flat?
#5 carburetion or ignition or oil consumption issues leading to either (A) carbon build-up or (B) overheating.

Are you running the engine without a good air filter? If it's ingesting dust, all bets are off.

Does this engine have valve stem seals? A lot of older stuff didn't and was designed not to. Whether retrofitting valve stem seals is a good thing to do or not in that application, is above my pay grade.

 

[mfgenggear]

Op
In general the lead might be to verify how healthy the engine is.
Compression test, leak test, excessive valve guides cause excessive oil usage.
And the main verification how is the oil pressure. If it is a 4 stroke,
A 2 stroke will be other issues. But 2 stroke don't have valves.
I do t know how one would measure oil flow except for visual and enough oil pressure.

 

[waross]

Valve guide wear is common on older engines designed for leaded gasoline that are now running on unleaded gasoline.
I understand that there are specific fuel additives available to remedy this.
Google away.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[waross]

ps: The older valve stems were lubricated by the Tetraethyllead in leaded gasoline, not by the lube oil.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[TugboatEng]

The material pairing between the valve guide and the valve stem is crucial. When buying aftermarket, very few manufacturers will tell you what the stem material is. The ones that do I believe are not even telling you the correct material. You'll hear the names Stellite and Inconel kicked around but I don't believe these were ever widely used in automotive or racing applications despite many manufacturers claiming to use them. Stainless steel is common but they're fairly unfamiliar alloys to most. Nitronic and Nimonic are used by OEMs for modern engines. These alloys can exhibit very low wear rates in low lube applications. They pair well with many alloys. Long lasting engines regularly use steel and iron valve guides with these valves combinations as they don't require a soft pairing due to high galling resistance.

 

[BrianPetersen]

waross - ... and this engine would have been designed before unleaded petrol. Seems hard to find much information on whether anything is needed on the older Royal Enfield engines to accommodate this. Any search of the internet seems to only turn up information on the new ones.

https://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=310784

(Not pertaining to Royal Enfield)

https://laverdaforum.com/threads/unleaded-fuel.88960/

(Not this one, either)

https://www.jandeengineering.co.uk/unleadedconversion.html

(general automotive)

 

[Lou Scannon]

The older valve stems were lubricated by the Tetraethyllead in leaded gasoline, not by the lube oil

Do you have a reference for that? I haven't heard it before, and I've been around a while

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

 

[mfgenggear]

I can or can not say that leaded gas was important valve guides but it was for all the other components. Especially the valves. Prevent them from warping.
But can say that lubrication was important to the valve guides. Infact
Ever heard a valve train when starved for oil. Noisy. It is very important
For lubrication.. it will flatan a cam in a hurry

 

[TugboatEng]

Let me answer your question in a different way. You're experiencing normal wear. You're not used to wear at these rates because you're also used to modern materials. You need to focus on upgrading to modern materials if you want familiar wear rates.

Remember, valves oscillate so they don't experience hydrodynamic lubrication. You aren't going to fix your problem with more oil.

 

[477stephen]

Thank you all for your input,
Sorry but Valve guides go from boundary to mixed film to at best full film mid-stroke So they need a Q ( quantity ) of oil.

2;
This is the problem Ive got, Even with "modern materials the valve guides are not getting enough oil so basically are running ( one could say ) dry

3 you are thinking of "valve Seats" Valve guides are different ( inlet under negative intake pressures , exhaust under positive pressure )

folks basically what I've got here is a "Linear sliding bearing " I need a formula, text or a number so that AT mid stroke a have some kind of oil film height. an example Sliding friction exists in the working process of sliding bearing. The advantages of sliding bearing include the stability, reliability, and noiseless. Requirement of the formation of lubrication film is to ensure the sufficient lubricant for the sliding bearing. Under the condition of liquid lubrication, the surfaces of the sliding bearing are separated by lubricating oil and there is direct contact, so the friction loss and the wear of the surface can be reduced greatly. Besides, the lubricating film also has a certain vibration absorbed performance. In this chapter, the basic theory of sliding bearing lubrication will be introduced, on bases of which the reasons of sliding bearing lubrication failure can be analyzed further, and finally, establish the foundation for seeking the effective way to solve the problem. One of the OLDEST bearings in the world

Hope I'm making sense here ( google is useless )

Stephen

 

[mfgenggear]

OP
I have a lot of small engine mechanical repair experience. And old school automotive engine repair.
If there is considerable wear on the engine components and the oil pump
It will have low oil pressure.
In the old days, an oil pressure gage would be added to monitor oil pressure.
We loved it at 40 PSI or higher, and frowned at 10 PSI or lower.
Engines with lower or worn components
Required old style oil lubrication.
And synthetic or lower viscosity
Would ruin your engine.
Synthetic is fine for new very close tolerance engines.
Here is a tip.
An engine oil flush will clog up the small oil holes and lube tube.
All the burnt oil and accumulation of sluge is the enemy.flush the engine
And evacuate the sluge.
These old engine like the old fashion type of oil at 30 weight USA.
It's not done any more .
If there are seals and o rings care must be taken not to damage them with
Chemical clean. So becareful.

 

[477stephen]

Hi
mfgenggear

yes I am aware of all that, Its a number, textbook, or formula I'm after, I mean a sliding bearing ( guide bearing) is just a rotating bearing with a "very big circumference " I mean Mid stroke there should be enough "oil! to cover all the sticky up bits with a "clearance sealing at both ends ( i can find the surface roughness and Eccentricity and guess from there )

The Enfield engine is a quantity lubed engine and basically is zero psi hot ( a handful of psi IF you are lucky )


I think my next step will be to email a valve guide supplier of a bearing manufacturer

Thanks for the input

Stephen

 

[3DDave]

Since valve guides are never force lubricated, what's the concern with oil volume?

Keep in mind it is a guide, not a bearing. Ideally there is no load on the guide from the valve stem, unlike typical bearing applications.

 

[waross]

The older engines that I am familiar with had seals to prevent oil from entering the valve guides.
Oil pressure or lack thereof did not affect valve stem lubrication.
Valve seats were an even greater issue without leaded gasoline.
Here is a conversion of an older engine.
Link
Google;
"old engines unleaded gas"


--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[3DDave]

The seals are there to prevent oil pouring down the open gap; they are designed to leak a very small amount of the oil that is splashed about.

 

[mfgenggear]

Yes they had seals to prevent excessive oil slipping through, but did require a small amount for lubrication.
And that was the nature of the 8, 6 and 4 cyl. Valve guides would wear after 100k miles.carbon build up would case issues. But the valve train requires plenty of lubrication.

 

[mfgenggear]

Those old style motor heads were a breeze to work on. As a matter the entire engine could disassembled and reassembled in a week end. Fun days