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

 

[XR250]

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.

There is a side load on the valve from the rocker unless it uses a bucket arrangement.

Also, I think lead was for valve seats, not guides.

 

[3DDave]

If there is a side load from the rocker, there is a side load on the place the rocker contacts the valve stem. Won't that cause the end of the valve stem to wear the rocker?

It is a good point that a poorly located rocker will do damage to the guides.

 

[MintJulep]

I don't have any directly useful contribution for you, but I am curious.

If you do find the magic number, what will you do with it?

What will you change in the engine to achieve the magic number?

 

[477stephen]

Please excuse the reply Im not sure how to "quote peoples reply so Im cut and paste

" 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. "
Reply; I gave the amount in the original post " 0.007 to 0.1 cm^3 / 10 hours"

2: " There is a side load on the valve from the r•
Qote"
Friction action at the end of the valve (Fq)
The lateral forces exerted by the valve spring (Ff)
The standardized eccentric force on the end of the
valve (Fn)
When running dry, the loading at the ends of the valve
guides causes metal-to-metal contact with the valve stem.
Oil inside the valve guide forms a hydrodynamic lubricat-
ing film as a result of the valve's reciprocating motion;
pressure is developed at the ends of the valve guide. This
lubricating film separates the mating surfaces through to
the point that the motion is reversed. Then there is a brief
period of direct contact between the surfaces' solid bod-
ies, which then reverts again from adhesive sliding to slid-
ing action. In principle, the contact between the valve
stem and the guide cycles continuously through the fric-
tion situations described in the so-called Stribeck curve,
depending on the sliding velocity. The following items
influence loading inside the valve guide:
Valve guide clearance: The valve guide is responsible
for exact positioning of the valve in the seat at the
valve seat insert. To ensure that this task is fulfilled,
the valve guide bore and the outside diameter of the
valve stem have to be sized to match one another,
always striving to achieve the smallest possible
amount of play at the valve guide. In addition to im-
proved heat transfer, the hazard of the valve's tipping
is reduced. Moreover, this geometric matching of the
mating components supports the establishment of
the hydrodynamic lubricating film. The lower limits
for the difference between the diameters are deter-
mined by the divergent coefficients of thermal expan-
sion for the guide and the valve stem.

The forces exerted by gases on the valve disk (Fgas)ocker unless it uses a bucket arrangement." Reply; there is also a small side load from the spring and gas pressure as well as you pointed out Rocker geometry which strangely mine ain't terminal !)

3; "If there is a side load from the rocker, there is a side load on the place the rocker contacts the valve stem. Won't that cause the end of the valve stem to wear the rocker?

It is a good point that a poorly located rocker will do damage to the guides. "
Reply: Which is why we have a carrier oil to minimise the friction\wear in the boundary zones( top and bottom )

Which is my ORIGINAL question Who much oil !

I have a surface roughnes Ra of about 0.05 micrometres ( from memory don't quote) I have a clearance of 2 thou, fo U could possibly work out a film height required ( roughly) and go from there or use thrust bearings as a "guide " pun intended

I would have thought valve guide lubrication info would be readily available appears not

Finally, Yes these old bikes

I have this old Enfield as a daily driver, as it ain't worth a lot ,,,I can change it without destroying "history" It starts basically 1st kick , will nun on the tiniest of spark and if it does go wring 15 min later the entire top end of the engine is apart

When I left Honda back in the mid 90s it took half a day just get AT the engine ( well an hour or more ) you should see some of the bill people are being presented with for a simple job that on an Enfield is a hand full of min

 

[477stephen]

Hi there
Quote "I don't have any directly useful contribution for you, but I am curious.

If you do find the magic number, what will you do with it?

What will you change in the engine to achieve the magic number?

I need a idea of flow required, as I will quite literally give the guide what it needs. I Have designed and am testing needle roller rocker arms this allowed more oil to flow through the rocker block and be used for the valve guides, but even with that the oil isn't reaching areas as well as it should so Im looking at either a direct feed or "cup" ( machining of a new spring holder )
Now these old bikes don't use a stem seal So IF i over oil it I will have to add a seal ( so I need an amount.an Idea OF the amount ... its called prior planning )

I cant really increase the feed to the rockers without a ton of work ( all the passages need to be opened up accordingly to keep pressures down or the same ) as the oil pump drive is weak and just adding a bigger pump without opening up all the feed passages, stresses the teeth of the drive and they fail ( ask me how I know hahaha)

Right now the Modern valve guides are not getting enough oil and have a high wear rate it's a design fault on these machines and lead to the typical noise you hear from these engines

 

[TugboatEng]

I strongly suggest reading this article:

https://nickelinstitute.org/media/1...lingcharacteristicsofstainlesssteel_9006_.pdf

 

[MintJulep]

Perhaps you'll find something of use in one of these books or papers:

Good luck.

 

[477stephen]

Thank you
One thing ive discovered fro this question is

BUY / SAVE books the information ( I think ) is disappearing Im actually a little "shocked" at what I thought would be a simple question ,,,

Buy old books and keep them ! Thats my xmas and birthdays done for the foreseeable future!

Stephen
Ps, I have a love hate relationship with stainless ever since as a YOOF i tried to drill a hole in a stainless rod with 118 deg bit and an electric drill oh the joys !

pps
Yup this is where I'm at

lube as Materials are set ( unless anyone knows a good sintere4d guide maker !)
Design Considerations
1. Lubricate where possible.
2. Keep load, temperature, and speed as low as possible. cant change
3. Start with mated surfaces having a finish between 10 and
70 microinches. (Below 10 increases susceptibility to
galling; above 70 increases susceptibility to wear.) ( reaming Ra = about 2 about 70 microinches , So can surface finish a bit better here
Seizing of Threaded
Couplings
Design Considerations for
Reducing Galling
and Wear
16
4. Increase contact area: (Make a guide longer to lower the tipping angle of valve )
a. to lower stress below threshold galling stress. not a concern
b. to produce less depth of wear (by spreading the
wear volume over a greater area).
5. In unlubricated systems or where the lubricant may not
always be present, alloy selection is critical. Therefore,
it is desirable to:
a. select alloys with high threshold galling stresses
as one mating surface for significant
improvement in galling resistance.
b. use dissimilar alloys and/or those with differential
hardnesses on the sliding surfaces to achieve
somewhat lesser improvements in galling
resistance.
c. select high work-hardening austenitic stainless
steels for improved wear resistance (but not
galling resistance) at temperatures below 350ºF
(175ºC).
6. Consider the use of wear coatings. considered ,,,Im using Kibblewhite valves which are already coated

 

[3DDave]

If it was simple then engine designers would not have test stands for durability testing.

 

[TugboatEng]

What do you think your valves are made from right now if it's not a stainless material?

Drilling stainless is fine. The mistake most make is not using sufficient feed pressure.

 

[477stephen]

Hi there

Quote"If it was simple then engine designers would not have test stands for durability testing." Its not difficult ( to get a good estimate) its just we cant access the required " reading"

https://www.youtube.com/watch?v=72qsY0g6B8I

and chapter 3 of this book as suggested earlier ( $100 dollars though ! ) Hence I tried to turn to the internet as per the original post ...I "thought it would have been easy to find the info ,,,"

TugboatEng (Marine/Ocean)
6 Sep 24 03:45
What do you think your valves are made from right now if it's not a stainless material? ( Have a valve in front of me now , Non magnetic so most likely Stainless , I can check later , The valve shows wear , through a coating 30mm from seat to 45mm from valve seat seat and light wear at top showing the base of the guide taking the most load/ )
""
Drilling stainless is fine. The mistake most make is not using sufficient feed pressure. (electric drill, and a " Yoof" and a bar of stainless a surefire method of straightening out a twist drill! )

Kind regards
Stephen

 

[TugboatEng]

If you can straighten your twist drill without breaking it, then it was not properly heat treated. I have seen this happen.

Only the 300 series of stainless steels are non-magnetic and even some of them are magnetic, especially after cold-working.

 

[477stephen]

TugboatEng (Marine/Ocean)
6 Sep 24 04:53
If you can straighten your twist drill without breaking it, then it was not properly heat treated. I have seen this happen. ( teenager, electric drill , fathers drill bit and making a back rest for chopper , yes them were the days,,, there was glowing metal smoke and very little forward motion by the drill .....)

Only the 300 series of stainless steels are non-magnetic and even some of them are magnetic, especially after cold-working.

Yup......

https://shop.kpmi.us/products/valve-black-diamond-stainless-std-in-polaris-various-1000s-2015-2023

but "are impregnated by a special German process" ooo err one wonders ...

Stephen

 

[mfgenggear]

As we can view there is no 100% answer.
It appears it's Avery simple design.
Opening up orifices is not advisable.
Might even make it worse. It depends on
The pump, capability and built in pressure.
I would say just replace thr valve guides, and rework the valve seats, and or replace the valve. I am sure after market have the latest materials.
Simple to rework and may be the answer.

 

[BrianPetersen]

Agree: Modernize both the valve guide and the valve itself in terms of material selection and tolerances. I would seek out the advice of a good valve manufacturer and, if possible, buy both the guides and the valves from the same supplier. Make sure the valve seat and guide machining is dead-nuts.

The oil supply is not an issue as long as it is not zero.

 

[mfgenggear]

Yes also R & R the oil pump. I don't know the design but it does wear out.
Causing decrease efficiency and oil flow. Check for leaks make sure all mating surfaces are flat, and are mating properly. A complete dis assembly and very all components are to spec and replace all gaskets. If the cylinder
Is not to worn a rering while doing a valve job is advisable. I like doing a rering or reborn over and replace piston and rod. Regring the crank, with o/s
Bearings makes big changes and better
Oil pressure, and she will purr like a kitten.

 

[477stephen]

[highlight #3465A4]Quote;" As we can view there is no 100% answer.[/highlight] ( there is , its just its not readily available ,,the texts given earlier were good and provided the answers ,,but 100 dollars yikes ,,,

[highlight #3465A4]It appears it's Avery simple design.[/highlight] Simple but clever a double acting piston pump

[highlight #3465A4]Opening up orifices is not advisable.[/highlight] Sorry may not have made myself clear, You open up the passages IF fitting a larger feed pump piston ( offered as an "upgrade") The larger pump stresses the oil pump gear teeth which then fails and things become expensive ,, The bike is a QUANTITY fed system not a PRESSURE system So while a larger feed is good the whole supply train after that piston needs to be addressed ( ask me how I know hahahaha)

[highlight #3465A4]Might even make it worse. It depends on The pump, capability and built in pressure.[/highlight] see above
[highlight #3465A4]
I would say just replace thr valve guides, and rework the valve seats, and or replace the valve. I am sure after market have the latest materials.[/highlight] Which is what I have done and as I type I have a very modern valve sitting in front of me with unacceptable wear ( as I have previously said )
So, again it isnt getting what it requires
OIL
As I said I will address the oil feed and direct it to where its needed THE trouble being IF its too much for this older Non valve guide seal engine I will have to fit an seal ( which I have on my race bike ) I was or AM doing the old Prior planning thing Which is WHY i was asking for texts or a number, ( which now I have a lead on ,,,much appreciated )

I will Email Kibblewhite the manufacturers of the valve and guide and see what they say The guides wont need much but they certainly go need more that they are receiving at the moment

thanks for all the input

Stephen


Simple to rework and may be the answer.

 

[477stephen]

Brian
you might want to reword this "
The oil supply is not an issue as long as it is not zero."

Stephen

 

[XR250]

In high school power mechanics class, we used to do a thing called "knurlizing" the valve guides in old V8's. It was a process where grooves where cut into the guide along its length to help hold oil.

https://www.yesterdaystractors.com/cgi-bin/viewit.cgi?bd=farmall&th=511579

Maybe that would help.

 

[477stephen]

Hi Xr250 ( Cr250r are better though )

As was noted in that thread;
Replacing is much better than knurling because a knurled surface wears 70% faster because of the missing surface area.

Knurling is a stopgap repair at best; kinda like putting new rings against an old worn cylinder wall. (I've never understood the logic behind that one either).

Its not the guide itself that is the problem both are of modern materials finish, its the lubrication feed I wont say its running dry ,,,but a dash more wouldnt go amiss the point of this thread is how much more

Thank yo for your input

Kind regards Steph