More Big Valves

[petert 586]

For some time I've been working on these new inlet valves. The development is almost complete and then I'll start selling them. In all development work there has to be compromises. Every effort was made to keep the weight down, maximise compression and yet retain acceptable flow. You'll notice the faces are flat, rather than dished, in order to maximise compression, which is so important in an Mi16 engine. Other key features are the 6mm wasted stem, 30 deg. back cut and the single collet groove, which enables the use of the more reliable Kawasaki Z900/1000 collet in the standard retainer. The valves shown are 120mm long stem versions, which weigh the same as the standard 105mm valve. The standard length valve weighs considerably less. Lighter, single groove exhaust valves will also be available.

Edited May 7, 2006 by petert

[B1ack_Mi16 67]

Looks nice

 

Are you using all the standard Mi16 valvetrain components then, and just changing the the collets/locks?

What will the price be, I have several Mi16 heads which have had the cambelt snap.

 

Btw.. It's nice to have them in a dished version also, for us making 2.3 litre conversions it's actually hard enough to get the compression down to acceptable levels

[PumaRacing 2]

I think you're developing things for which there isn't going to be a lot more long term interest. When I launched the 36.5mm valves for the Mi16 a couple of years ago they sold very fast. However I think most of the people who want a big valve head now have one and demand has more or less dried up, happily coinciding with the last of the original batch so it all worked out quite nicely. I can't see me investing just yet in another batch most of which might not sell.

 

Also yours need special guides and collets (and maybe even caps?). The standard guides rarely wear so that's adding £100 or more of unnecesssary cost to the job. People don't generally want products that require a lot of work to fit. I've never seen a failure with a triple groove valve if the material is right so I can't see many people wanting to spend a fortune fixing something which ain't broke.

[petert 586]

Sorry, my mistake earlier. They have the standard 7mm stem diameter, wasted, and thus take 7mm x 7 deg. collets, the same dimension as standard. Whilst the multigrooves don't fail on street engines, they do swell however, which can only lead to less than perfect locking. Most standard valves around now ream the guide on the way out anyway. Who'd put them back in? Given that the Z900/1000 collets are so cheap, and rated for 10,000+ RPM, I think they're a logical choice. Naturally, each set will come with a set of collets anyway, which enables them to be used with standard retainers. However, titanium retainers are also on the horizon. These are definitely aimed at a small segment of the market, being a serious competition valve. I'll put the prices on my new website when it goes online.

 

Most Mi16 heads I do seam to need guides. It must be the warmer climate!

[B1ack_Mi16 67]

About reaming the guides when dismantling the head that seem to be the case if the engine have done lotsa miles/kilometres. Most 200000km+ engines I've dismantled the head, the inlet valve will bring with it material from the guide on its way out.

 

What's the address of your webpage then?

[petert 586]

sorry, it's not up yet.

[PumaRacing 2]

It should never be necessary to harm the guides when removing a valve. All that's needed is to gently file any burrs off the collet grooves first if they've lipped up. It's a common problem on the triple groove type valve because of the way the collets seat in them but it doesn't ever lead to a valve failure and it doesn't occur on properly heat treated valves. The Ford CVH and Pinto valves have triple grooves but are heat treated to a very high hardness spec and don't lip up. The Peugeot ones are heat treated to a lower spec and sometimes do have burrs on them.

 

It's also why triple grooves should never be used on stainless steel valves because stainless can't be heat treated at all. I've seen some shocking groove wear on 'race' valves for the Pinto and CVH simply because people use the wrong material for them. I even know of one large Ford performance parts supplier who admit the problem on all of their stainless valves and say they intend to do nothing about it because it means they get to sell another set of valves every time a customer rebuilds their cylinder head.

[petert 586]

.......................... stainless can't be heat treated at all.

 

It depends whether they're martensitic or austenitic. Standard Mi16 inlets are martensitic, whilst the exhausts are austenitic. Try a magnet on them.

Edited May 8, 2006 by petert

[PumaRacing 2]

It depends whether they're martensitic or austenitic. Standard Mi16 inlets are martensitic, whilst the exhausts are austenitic. Try a magnet on them.

 

The EN52B martensitic material used for inlet valves isn't a stainless steel. It's got a high chromium content and is somewhat 'corrosion resistant' but it isn't stainless. Exhaust valves are two piece. A 21/4N austenitic stainless steel head and lower stem friction welded to a heat treatable EN52B upper stem to allow the collet grooves to be hardened. A magnet will let you find the split line between the martensitic magnetic upper stem and the non magnetic head and lower stem.

 

If you abrade the chrome off and put an inlet and exhaust valve in water for a couple of days you'll soon find out which bits are stainless or not. Only the head of the exhaust valve.

[petert 586]

and isn't nitriding a H/T process?

[PumaRacing 2]

and isn't nitriding a H/T process?

 

It's a treatment that involves heat if that's what you mean but it's not what I was referring to. Martensitic inlet valve steels, of which EN52B is the main one, can be heated and quenched to radically increase their hardness right through to the core. Austenitic stainless exhaust valve steels, of which 21/4N and 21/2N are the main ones, can't. Surface treatments like tuftriding and nitriding put a thin case of harder material on the surface of the steel but don't affect the core hardness. They are primarily used to increase sliding wear resistance between the valve and guide, especially if cast iron or sintered guides are used. However chrome plating is still the main coating for this purpose.

 

The reason triple grooves distort is threefold.

 

1) The very small groove and collet bump radius means the collet contacts the groove close to its outer edge.

 

2) The fact there is more than one groove means that manufacturing tolerances on the groove spacing of the valve and collet leads to only one groove taking the brunt of the load unless the valve distorts to allow all three grooves to make full contact.

 

3) The collets on triple groove valves are designed to abut each other before they lock onto the valve stem. This was meant to allow the valve to float and rotate inside the two collets and even out wear on the valve seat. IMO it's a redundant feature because valves rotate anyway complete with their collets. So the valve actually bounces around inside the two collets instead of being gripped tightly which leads to groove wear. On high rpm engines I linish the collets of triple groove valves until the collets grip the valve stem tightly instead of abutting and letting the valve stem float inside them.

 

If you take a triple groove valve and two collets and put the collets into position you'll find you can grip the collets and still rotate the valve inside them. It's a very bad design feature which some manufacturers still espouse and others have never gone for. Early A series Leyland engines had a single groove for decades but for some reason they went to triple groove on later Mini Metro engines. Ford have always used triple grooves on engines such as the Crossflow, Pinto, Essex V6, Cologne V6 and CVH. However the early Zetec engines from 1993 had single grooves which changed back to to triple grooves after 1998. Peugeot have used single grooves almost exclusively with no apparent problems but went to triple on the 2.0 8V engines, the Mi16 and the TU.

 

What determines these choices is something of a mystery. However it's undeniable that unless the collet is very accurately made and the valve hardened to very high Brinell levels the triple groove will cause problems in the long term. I always prefer a single groove and preferably of a large radius so that the contact area is well away from the o/d of the valve stem. When faced with triple grooves I make my valves of a material which can be hardened to the Ford specs rather than the Peugeot ones so the valve doesn't distort in use. That eliminates 21/4N and other austenitic materials other than for the valve head and that's why my valves last the life of the engine rather than failing after a season or so.

[petert 586]

I'm not sure how you'd do a Brinell test on a collet! Or which Brinell scale you meant, but probably the equivalent of 20-25 Rockwell C.

 

So what you're saying is that your valves have a homogenous martensitic structure?

 

Conversely, it might be more desireable to choose a mat'l with less mass hardenability, and end up with a martensitic skin and ferrite/cementite (pearlite) core. The equivalent mechanically of what's achieved with a nitrided austenite stainless?

 

Whether the hard skin (nitrided or martensite) is better than chrome is another lengthy debate. The surface of chrome retains oil making it ideal for valve stems, rather than the actual hardness of the chrome.

 

I developed the valve with the help of a local competition valve manufacturer. So their manufacturing processes have been well and truely tested in the local racing arena. An earlier version of the single Z900 collet valve has already successfully completed two seasons. My main involvement has been to develop the head/seat profile. A process which I know you mastered some time ago! I still need to do one more flow test to confirm I'm there.

 

Have you read "Introduction to Physical Metallurgy" by Avner? Compelling bedside reading, along with the "Machinery's Handbook"!

Edited May 9, 2006 by petert

[PumaRacing 2]

I'm not sure how you'd do a Brinell test on a collet! Or which Brinell scale you meant, but probably the equivalent of 20-25 Rockwell C.

 

Struth no. That's not even semi-hard. A properly made valve with triple collet grooves wants to be about 50 Rockwell C in the groove area and on the tip. So hard that a sharp file only just touches the material. Try getting a Pinto or CVH valve and filing the tip. You can't, or only just. The valve is almost the same hardness as the file.

 

 

So what you're saying is that your valves have a homogenous martensitic structure?

 

I use only EN52B for my inlet valves. The same material as most major OE manufacturers use even in turbo engines. This current nonsense that 21/4N stainless is a 'better' material or a necessary material is just plain wrong. What has happened though is that many 'performance' valve manufacturers get asked for 21/4N for everything so they no longer even stock EN52B so it actually becomes more expensive for them them to get some in and use the right material than use the wrong one. So if you go to them and aren't too specific about the material you want they just tell you you want what they keep in stock - 21/4N

 

For exhaust valves you really do need 21/4N for the head of the valve but I've never yet come across an application where bigger exhaust valves help the engine in any way so I've never had to make any. If I ever did I'd use one piece 21/4N for valves with single collet grooves and two piece with hardenable EN52B upper stems for triple groove valves. In both cases they'd be chromed or nitrided as per my inlet valves.

[petert 586]

The inlet valves above are tufftrided 21/4N. You can't nitride 21/4N successfully.

[Rippthrough 98]

Peugeot have used single grooves almost exclusively with no apparent problems but went to triple on the 2.0 8V engines, the Mi16 and the TU.

 

 

Single's on my TU

[PumaRacing 2]

The inlet valves above are tufftrided 21/4N. You can't nitride 21/4N successfully.

 

I hope it wasn't your valve manufacturer who told who that but it's nonsense.

 

http://www.supertechperformance.com/technology.htm

 

http://www.gsvalves.co.uk/Download_Files/VALVE_SPEC.PDF

[petert 586]

A good read. I was always under the impression that you needed a high iron content to nitride successfully. 21/4N is mostly nickel.

[PumaRacing 2]

A good read. I was always under the impression that you needed a high iron content to nitride successfully. 21/4N is mostly nickel.

 

I think you're getting mixed up with Nimonic. 21/4N is an austenitic stainless iron alloy with about 20% chromium and 10% Manganese. Nimonic is the family of alloys that are based on Nickel.

 

here's a post of mine from back in 1999 that covers the basics of what valve steels are made from.

 

http://yarchive.net/car/valve_steels.html

[petert 586]

I was aware of Nimo. We used a lot of it when I worked at BHP. Found this usefull info. Obviously there's plenty of iron in 21/4N.

 

http://www.kalyanicarpenter.com/21-4-nvs.htm

Edited May 9, 2006 by petert

[Guest Nuno205Rallye]

I read your opinions with great pleasure

 

 

What are your thoughts about nickel based materials such as Nimonic and Inconel for valve materials?

[petert 586]

Inconel is used for exhaust valves. I'm unsure about Nimonic however. I was confusing it with nimo, a nickel-molybdenium iron based alloy we used to use with a high resistance to chemicals.