Valve Guides
 

We have been concerned about the type of valve guides used in 911 engines for a while now and the wear we commonly see on exhaust guides is often greater than we would expect.

The material commonly used is specified as 'Manganese Bronze' and very little other detail is provided.

The family of Manganese Bronzes covers a wide range of characteristics.

In terms of coefficient of friction, strength, wear resistance and thermal conductivity the most suitable of the Manganse Bronzes clearly work and they are quite easy to machine but the last few years has seem some very good advances being made in terms of performance and what seem to be better materials have become available.

Modern CNC machining and the use of tipped carbide tools has allowed different alloys to be used and some of these have much better properties and should allow a 'better' guide to be manufactured.

Columbia Metals make a wide range of Bronzes and the material that they recommend for valve guides is sold under the Colsibro brand name.

This material is a precipitation hardening Copper/Nickel/Silicon ally that has excellent strength, resistance to galling, low coefficient of friction and a Thermal Conductivity that is much higher than any of the Manganese Bronzes.

It is a material of choice for many F1 and LeMans engines and is used by companies such as GS Valves for all of the guides they sell in their Race Engine Components catalogue.

We have now made 911 guides using Colsibro to a industry leading standard. All basic dimensions are within the tolerances shown in the Porsche Technical Specifications with the concentricity of the bore of the guide being within 0.025mm TIR.

We have achieved this level of accuracy by honing the bore and then cylindrically grinding the OD using a precision mandrel.

http://i197.photobucket.com/albums/a...psuwsi03fe.jpg

Very Purty :D

Is the Valve Guide SEAL in the picture made by you as well?

I would love to see a knock off on Fulljames' rocker shaft sealer.

What interference fit are you using? How do they measure after installed?

And wondering if there's a reason you've gone with the shoulderless type?
I'm lazy and hate having to measure the height on install.

Will they be made in several oversize OD s, or am I wrong that the guides bore in the head gets larger with each guide replacement?

Where to start.

1. We don't make the seal we buy them.

We are planning a re-design using a new seal system developed by a UK company which reduces the size of the seal and allows a slightly longer guide on the outer side and still clears a high lift cam.

2. Interference is on the high end of the Porsche Spec as we are grinding to very precise limits.

The modulus of the material is within 1-2% of a Manganese Bronze so installation should result in a similar ID to a standard guide.

I discussed sizes with a company that has made Colsibro guides for a few years and they always manufacture to standard sizes and fits.

3. As a first step we have just tried to make a standard style of guide which we hope to develop further as we progress.

4. We make them standard, 1st and 2nd Oversize.

We always machine out old guides rather then press them out so we use more standard size than any other.

I have seen Autofarm Shaft Seals but not the Redtek parts.

I have some concerns about the Autofarm Seals and the way in which the O ring is applied.

If you carefully model the Autofarm Bushes/Nuts and O rings you will see that the wedge shaped trapped volume is smaller than the volume of the O Ring that is used as a seal.

I would accept that the O ring will change shape BUT rubber is incompressible and so it will constrain the nut and load will transfer through the rubber and into the cam carrier.

The load will not 'spread' the end of the rocker shaft as the tapered nut will not engage with the shaft.

http://i197.photobucket.com/albums/a...psv0zn3od1.jpg

I am sure that the seal will work but I believe that the shaft will be held in place by the force applied to the seal and the resulting friction.

If the rubber then takes a set and the stress relaxes the shaft may not be well secured.

This design is also said to be patented ;)

To overcome this problem is more difficult than it initially appears.

To re-design the bush and the nut so that they will work with an O Ring that complies with the requirements of the Parker Hannefin Design Manual is quite tricky.

We would need to make a slightly shorter shaft so that the Bush/Nuts don't stick out past the ends of the cam carrier.

This means that the reduced cross section would be shorter and the load for a given clamping force would increase.

If we make the shaft from a Grade 5 Titanium this would solve the problem and mean clamping would improve even with a shorter reduced section.

A grade 5 titanium would have more than sufficient strength and by adding a PVD coating of Titanium carbide would have excellent wear resistance.

We could them design an O ring that doesn't infringe a patent and works correctly, allowing the shaft end to expand and clamp.

http://i197.photobucket.com/albums/a...psebbbvg67.jpg


We have already manufactured the custom Sized O Ring in a Green Viton A and the shafts, Bushes/Nuts and a custom are being manufactured as we speak.

We have made prototypes which we have used for static 'push out' tests which have been successful.

What lubricant are you using with your guides?

Is the Patent Porsche Specific? I am sure it cant be associated with Porsche in any way? A text search did show only publications close to the description but nothing resembling what we are doing..

We normally install with Sunnen B200-L Press fit assembly lube.

This is the statement Autofarm make about the patent.

'Autofarm has now designed (and patented) a solution that will keep your engine oil-tight however leaky your rocker shafts are.'

I have searched the European Patent Register, which includes all UK patents, fairly well using all of the conventional techniques and not found anything.

The cost of a patent and its maintenance is quite significant and by changing to a design as shown in the Parker Manual must mean that there can be no conflict.

I don't really want to copy Autofarm's design as this doesn't seem a good way to proceed.

Oh my, I would be willing to Beta test and provide reports via opening the covers for a full picture documentation when needed.

In any case, I will keep a close eye on your progress and look forward to hopefully seeing it in production soon.

One thing for sure this will save many from having to purchase a new/old Cam Housing due to a too wide of a rocker shaft opening/s.

Porsche says "tallow based lubricant"? when pressing in guides.

Does that mean I should use lard? Butter?

Apparently?

tal·low
ˈtalō/
noun
noun: tallow

1.
a hard fatty substance made from rendered animal fat, used in making candles and soap.

verbarchaic
verb: tallow; 3rd person present: tallows; past tense: tallowed; past participle: tallowed; gerund or present participle: tallowing

1.
smear (something, especially the bottom of a boat) with tallow.

Hey, what ever works best for our little princesses :D

That was in 1965 - I hope that the Sunnen Press fit lubricant has moved on a little.

If you want to stick to older ways this may help :)

http://www.theprairiehomestead.com/2014/01/tallow-emergency-candles.html

Lol :d

Actually tallow is what is recommended by Porsche the 84-89 Carrera Workshop manual as well.

So, without buying the Sunnen stuff what would you recommend be used? I have heard some use WD-40.

I am not really sure as we have used Sunnen oil for a long time

Many of the other products use a Moly Disulphide base which is generally black and looks messy on guides and I worry that they may affect the grip, which is why tallow was commonly used on Railway wheels and the like.

I can believe WD40 is used but it isn't a great lubricant and I am not sure I would adopt this.

Joking apart I am sure tallow will work but where do you buy it now?

This is great Chris. Thank you for continually pushing the envelope.

Craig... I have some heads for you to try these out on. :)

This should be over the top, but I couldn't resist. I searched for the Sunnen B-200l data sheet. Guess what, it is made from lard.:cool: http://www.sunnen.com/graphics/assets/documents/901e219280f2.pdf

Tallow in a bottle and tallow in a rattle can - and I thought we were buying something more modern :rolleyes:

I will in future deliver a bar of a suitable lubricant with every set of guides - or for cooking chips.

http://i197.photobucket.com/albums/a...pse0eusegb.jpg

Old thread and sadly Chris is no longer with us.

What's the latest tech on valve guides, is Colisbro an actual improvement over the old phosphor bronze material, which I believe Porsche still when you order their replacement parts?