Valves

[chris_seven]

I am sure that there are many strong views on the parts used in 911 Valve Trains and I would like to try to canvass some opinions into how to make some reasonable improvements. I am particularly interested in increasing engine revs to 9000+ on early 2.0 engines.

VALVES

Early Inlet Valves seem relatively straightforward and are just a bit heavy due to the 9mm stem.

I understand that quite a number of modified engines now use 7 or 9mm valve stems to save weight .

This may be an issue with FIA engines as strictly changing valve stem diameter isn’t quite within the regs.

Has anyone tried Hollow Stem Valves of even Titanium as a means of saving weight.

Early Exhaust valves were Sodium Filled and are supposed to conduct heat more successfully and they are substantially lighter.

I am not sure when they stopped using Sodium Filled valves .

Again using Hollow or Ti valves could means weights will match the stock valves.

Using either Ti or a hollow valve will reduce heat transfer from the valve, particularly when compared to a sodium filled valve.

Does anyone have experience with hollow or Ti valves to see if this is an issue.

VALVE LOCKS

3 groove keepers seem to work well but they do not clamp the valve.

When fully installed the valve is still free to rotate and this now seems to be non-preffered and many competition engines use single groove locks which fully clamp the stem of the valve and prevent rotation.

Any practical experience would be useful.

Hollow Valves

These seem more likely to fail due to increase stresses but the manufacturing route is similar to Sodium filled valves which don’t seem to have problems.

Titanium Valves look positive but Ti is not great in environment where it can fret.

It looks as if TI are valves are commonly coated in either DLC, Titanium Nitride or Chrome Nitride.

Does anyone have experience of the different coatings? I would be tempted by either TiN or Titanium carbide as DLC is just too costly.

Valve Springs

Has anyone tried Beehive Valve Springs as a way for eliminating valve bounce with a lightweight spring ? They seem like a good idea but may not be practical.

Any data/comments welcomed.

[chris_seven]

I can agree that standard valves are OK in standard engines but the range available for high rpm
engines seems limited.

As I said my interest is in tying to achieve 9000 rpm on a 2.0 litre as there it seems difficult t increase torque so the only way to get more horsepower is to rev it more and the inertia of the valves is an issue.

I also need to comply with FIA Appendix K and they wouldn't like 7mm dia stems.

[safe]

What about the shape of the valve, how important is that?

[Flieger]

So basically you are saying the inlet valve is the bottleneck and that the early exhaust valve is the best design for heat transfer and weight due to the sodium fill?

[chris_seven]

I think that the inlet valve, which is not, as far as I know, Sodium filled is heavy and in the limit will be the valve most likely to have problems following the cam.

If we increase the engine speed this potential problem could get worse and means that we need to increase the spring loads and this will them potentially wear cams and increase valve wear.

The Eibach High Lift spring set gives a significant increase in force as does the Shrick valve spring.

Andial springs also seem quite heavily rated hence my interest in lightweight valves.

It would also seem that a post has been deleted which makes my second post look a bit out of place as this was just a response to the deleted post.


If we can lighten the valve then the situation must get better.

I have seen an engine with a set of 7mm valves revving safely to 8700rpm but one day there will be a protest and it is not a path I want to follow.

I don't know how much heat transfer due sodium improves behaviour not its importance but the weight reduction is interesting.

I am not really trying to make statements just trying to learn what is being done.

[Henry Schmidt]

Over the years we have used titanium valves in both large and small engines.
We prefer Del West 3 groove valve for both intake and exhaust.
We had some issues with 3 groove retainers but by fitting each retainer by hand (lapping to tighten the fit) we cured all issues.
We easily see 200 hours without issue.
We run the valve against custom made seats using Amco 45 nickel-aluminum bronze.

These Valves are 39mm ex and 45 mm in for 69 S and 906

[chris_seven]

Henry,

Very interesting, one of my concerns about Ti valves has been the locks and the lack of clamping which I thought could result in galling.

Do you know the nature of the coating on the stems?

Also did your receive my e-mail about the MFI pump I need to source?

Thanks

[Henry Schmidt]

Originally Posted by chris_seven

Henry,

Very interesting, one of my concerns about Ti valves has been the locks and the lack of clamping which I thought could result in galling.

Do you know the nature of the coating on the stems?

Also did your receive my e-mail about the MFI pump I need to source?

Thanks

The valve stem coating is a dry-film moly similar to the CT1 coating we use on all of our bearings and rocker pads.
When we originally ordered the valves from Del West, they voiced a concern about the 3 groove approach as well but history has proven that hand fitting the retainers was a viable and reliable approach. We wanted a direct Porsche replacement and although custom valve seats proved to be desirable, our valves followed Porsche's design.
I believe my refusal to use excessively stiff valve springs (240 lb over the nose is my target number) has also contributed to our reduction in parasitic loss and improved longevity.

Chris
No email but I can search my spam filter. I get 200+ email a day and sometimes one or two will fall through the cracks.
We have almost every Bosch MFI pump in stock (sans 019 RS) and have some cool mods that improve functionality and form.

This is an 015 (2.4 T) pump sealed, with our RSR cover and hand enrichment device.