3/5/7 angle valve jobs?
Discussion
David Vizard said:
Right know I am trying to get him back to doing something that he is actually proving remarkably talented at (other than heads that is) - namely the writing of a scifi book. Read a few advance chapters so far and if I can get him to focus on it then I have a likely race car sponsor from all the money he will make when he sells the movie rights.
David Vizard
Next post, Mr. Pumaracing permitting, I will get onto something a little more technical!!
I think DV might be being rather too charitable about my penmanship skills, however without revealing too much about where the story goes from then on I've posted the first few chapters of what DV has already read on my website.David Vizard
Next post, Mr. Pumaracing permitting, I will get onto something a little more technical!!
http://www.pumaracing.co.uk/darol.docx
Hopefully next year I'll get on with finishing it.
Comments welcome.
Edited by Pumaracing on Wednesday 21st December 09:30
Edited by Pumaracing on Wednesday 21st December 09:38
Pumaracing said:
DaveL485 said:
The man who said "the standard valves melted in my 12v turbo-converted head after it was mapped".
Well, he didnt actually say that as he's French, but the valves melted and it was remapped (on an OE ECU with an EPROM).
I'm using standalone, but after spending several thousand quid on 1-off forged pistons, nitride coated rings and steel liners, plus billet cam to come and hopefully uprated springs when I get the valves done, its not a risk I want to take.
Well I only use OE valve steels in my own big valves and the highest power turbo engine they've run in without problem was 430 bhp at 2 bar boost in a 2 litre 8v ZVH engine. What I suspect you don't realise is that all stock exhaust valves have 21/4N stainless steel heads anyway and that's all anyone is likely to offer you as a "race" valve and inlet valves can't possibly get hot enough to fail unless there's something seriously wrong with the engine.Well, he didnt actually say that as he's French, but the valves melted and it was remapped (on an OE ECU with an EPROM).
I'm using standalone, but after spending several thousand quid on 1-off forged pistons, nitride coated rings and steel liners, plus billet cam to come and hopefully uprated springs when I get the valves done, its not a risk I want to take.
Whatever happened when your engine failed it wasn't the valves - more likely the person mapping it - or the seats had been badly cut and weren't concentric with the guides or maybe just a one in a million manufacturing fault with a valve.
I'm just not confident that going from a 2.0NA, 140bhp engine to a (planned) 350bhp, forced induction engine with an extra 1500rpm on the top end will retain its reliability. The 2.0 8v Turbo valves are sodium filled to assist with heat dissipation, for example.
For info the engine is a 2.0 8v Turbo J-Series Renault 21 bottom end, with a 2.0NA 12v head bolted on.
(Cue chastisement for using something French
)
Pumaracing said:
I think DV might be being rather too charitable about my penmanship skills, however without revealing too much about where the story goes from then on I've posted the first few chapters of what DV has already read on my website.
http://www.pumaracing.co.uk/darol.docx
Hopefully next year I'll get on with finishing it.
Comments welcome.
Not had a chance to read your stuff but you could do worse than putting it on authonomy.comhttp://www.pumaracing.co.uk/darol.docx
Hopefully next year I'll get on with finishing it.
Comments welcome.
Edited by Pumaracing on Wednesday 21st December 09:30
Edited by Pumaracing on Wednesday 21st December 09:38
Eta Fecking autocorrect
Edited by DrTre on Wednesday 21st December 13:21
Pumaracing said:
I think DV might be being rather too charitable about my penmanship skills, however without revealing too much about where the story goes from then on I've posted the first few chapters of what DV has already read on my website.
http://www.pumaracing.co.uk/darol.docx
Hopefully next year I'll get on with finishing it.
Comments welcome.
I had a read ... http://www.pumaracing.co.uk/darol.docx
Hopefully next year I'll get on with finishing it.
Comments welcome.
Edited by Pumaracing on Wednesday 21st December 09:30
Edited by Pumaracing on Wednesday 21st December 09:38
I'm not a great expert on written English but did notice 'Make mental note to self" .. as it you are writing as Darol ..
stevieturbo said:
As with most forums, this is a question and answer setup.
As for an article, and in keeping with this thread and recent experiences.
What about valve construction and design, and valve seats ?
There's info on that in the article on my website on unleaded petrol. I could easily expand it to cover more materials and design issues.As for an article, and in keeping with this thread and recent experiences.
What about valve construction and design, and valve seats ?
I do however have an interesting tech topic which cropped up while I was proof reading DV's new book on cylinder heads and on which I've had to email him some differing opinions but haven't heard back yet.
When a valve is say 50 thou or 100 thou or any other number of thou open how far is it actually open? That might sound daft but like all things engine related you really have to think about it hard. In other words what is the gap between valve and seat at a given nominal lift and what is the flow area that gap represents and which determines the amount of air flow that can take place? What aspects of the design of the valve and seat affect this relationship and what do they tell us about how we might get more flow out of a given valve size?
Conventional "wisdom" says that when a valve is open to 1/4 of its diameter the Curtain Area (Valve Lift x Valve Circumference) equals the area of the valve head and so in theory no more flow should take place. In practice flow continues to increase to lifts of 0.3 x valve diameter and beyond if the ports are correctly shaped. Understanding why this happens is key to understanding how to modify heads properly.
If anyone can actually derive from first principles the equations that determine valve gap and flow area versus valve lift then even more kudos but perhaps that's getting a bit too technical for a forum like this. However it's pretty straightforward if you have say decent A level maths or entry level university maths, understand the cosine rule and general aspects of trigonometry. Hopefully someone can have a crack at it.
stevieturbo said:
As with most forums, this is a question and answer setup.
As for an article, and in keeping with this thread and recent experiences.
What about valve construction and design, and valve seats ?
My response.
Hey - stevieturbo - how about not one article but, over a 12 month period, maybe 40 -50 or so all in color and some with video??? Lets hear it from all Pistonhead posters on that because it is a big commitment on my part.
On second thoughts it might not be that difficult to fill a magazine with truly hi-tech stuff written in great style. Here's my plan - all I have to do is start up a seemingly controversial subject and let Dave Baker respond. I just read his last post - so elegantly written. all I did was give him a nudge and 'presto' we get a page and a half of super tech well thought out and well written. What more could an editor ask for. Seriously though - thanks Dave for taking the time to respond with a bang up posting.
Also - and this is for all of you out there that are not Dave Baker. During the production of my cylinder head book I had some seriously serious health issues. Dave was not only a great moral support in some difficult times but he also helped do some of the math work when I was in the process of recovering from surgery. What with helping me forget my aches and pains and carrying some of the tech burden for me that book got finished at least 8 weeks sooner. Hopefully when it comes out in early 2012 you guys will buy it as a lot of effort went into it.
Now lets hear it about articles - and I mean I want some serious response here across all the forums headings here not just in this engine section - is it yes or no!
DV
As with most forums, this is a question and answer setup.
As for an article, and in keeping with this thread and recent experiences.
What about valve construction and design, and valve seats ?
My response.
Hey - stevieturbo - how about not one article but, over a 12 month period, maybe 40 -50 or so all in color and some with video??? Lets hear it from all Pistonhead posters on that because it is a big commitment on my part.
On second thoughts it might not be that difficult to fill a magazine with truly hi-tech stuff written in great style. Here's my plan - all I have to do is start up a seemingly controversial subject and let Dave Baker respond. I just read his last post - so elegantly written. all I did was give him a nudge and 'presto' we get a page and a half of super tech well thought out and well written. What more could an editor ask for. Seriously though - thanks Dave for taking the time to respond with a bang up posting.
Also - and this is for all of you out there that are not Dave Baker. During the production of my cylinder head book I had some seriously serious health issues. Dave was not only a great moral support in some difficult times but he also helped do some of the math work when I was in the process of recovering from surgery. What with helping me forget my aches and pains and carrying some of the tech burden for me that book got finished at least 8 weeks sooner. Hopefully when it comes out in early 2012 you guys will buy it as a lot of effort went into it.
Now lets hear it about articles - and I mean I want some serious response here across all the forums headings here not just in this engine section - is it yes or no!
DV
David Vizard said:
Now lets hear it about articles - and I mean I want some serious response here across all the forums headings here not just in this engine section - is it yes or no!
DV
You may be better posting a new thread with your request in the title to get the max feedback. DV
However, duplicate posts across other sections of this same forum, ie Pistonheads is frowned upon by the moderators. In otherwords they like deleting them.
In some cases it makes sense, in others it's just plain stupid.
David Vizard said:
Now lets hear it about articles - and I mean I want some serious response here across all the forums headings here not just in this engine section - is it yes or no!
DV
Dave, I think you have to recognise this is not the sort of forum for engine articles, especially technical ones as you can see by the staggering lack of response to the question I posed above. People mainly come on here to find out why their car won't start. They don't want to know how the rest of the engine works, they just want to know how to fix it.DV
If every now and then someone has a problem with a Mini or a Chevy engine or a Pinto or anything else you are reknowned for then it would be a kick for them to have their question answered by the one and only David Vizard instead of Joe Blogs or his dog. That's why I asked you on here. Just think of it as your couple of hours a week of charity work. As time goes by and more people find out you post on here then maybe the situation will change.
Personally I'd like a subsection under Technical in here for Engine Theory but I suspect the number of people who would read it could be counted on the fingers of the hands of a double amputee and the number who could actually contribute anything worthwhile to it would be fewer than that. Perhaps if you hang around in here until the word gets out that will change too.
Let's face it, even on GofastNews we barely had a dozen different people contributing to most of the technical threads. It was just the same few names cropping up over and over again. Most of the people who are interested in engines to the level of detail that you and I are either teach at a university or build top end engines for a living and in neither case do they have much time for yacking about it online to people whose heads it'll just go straight over.
Tell you what though. I've been biting my tongue like crazy to stop myself posting anything on the thread where the guy wonders if he can turn his 1.8 Golf engine into a 2 litre if he fits enough extra head gaskets
How about you have a crack at that one for us?
I'd better do this while I'm pished because I'll sure as hell regret it when I'm sober again.
To those of you who haven't had the privilege of knowing DV and being able to chat to him whenever you want I'll tell you a bit about him. I can honestly say with hand on heart I've never had a conversation with Dave I haven't come away from having learned something totally new or found a topic I suddenly realise I've not thought deeply enough about and have to get into it all over again.
Lord knows how we ever achieve anything sensible though. We might start off with good intentions of talking about a specific engine issue but 10 minutes later we're into particle physics or quantum theory or cosmology or whether you can make a mass driver to launch heavy items into space by drilling a hole right through a planet (that was one of Dave's mates Dusty's ideas and no it doesn't work). Then Dave will start yacking on endlessly about his race car driving exploits from time gone by and I'll have to sit there pretending I'm interested until I can steer him back to the engine topic again.
One of Dave's strengths is thinking outside the box and coming up with new ideas that no one else would ever think of. Google "polyquad" for example. A 4v head with one big and one small inlet valve and ditto for the exhausts. It gives the flow of a conventional 4v head but lots more swirl. Who the hell would ever have come up with that? Not me for sure. I tend to plod along with basic theory just optimising whatever I can but I doubt if I'll ever invent anything new nevermind patent it like Polyquad is.
It was Dave who immediately spotted the problem with my first flowbench design 20 years ago when I couldn't get the damn thing to measure accurately. I had a pressure tapping in the wrong place - stupid rookie mistake but easily solved. If it hadn't been for Dave I'd probably still be measuring flow inaccurately.
We disagree on lots of stuff though - which is probably healthy but often somewhat fraught. I think valve seats should have a width proportionate to the valve size so the geometry stays constant. Dave thinks they should always be 1.5mm wide whether the valve is 30mm or 60mm. I get where he's coming from in flow terms but then I also know what I've proved on customer's engines by cutting wider seats than most other people use. We'll probably go to our graves arguing about that one.
However, when I'm really stuck on some deeply technical and arcane engine issue and can't see the light at the end of the tunnel and no one else understands what the hell I'm banging on about I can phone Dave. He might not always have the immediate answer (although he usually does) but he'll always have something to say that'll get me thinking again and make me re-examine my ideas. It's hard to express just how valuable that's been to me over the years and how much I appreciate it.
The more I learn about engines the more I realise I still don't know. It's an infinite subject. All we ever do is scratch the surface and constantly reinvent the wheel that someone else has already done long ago but we didn't know about it. If most people knew just the stuff that Annand and Roe wrote about 50 years ago on cylinder heads they'd be much better engine builders.
Now I'm really off on one. I'm thinking about Crocodile Dundee II when the bad guys are looking for Mick and one of them comes across Nugget sitting on a box on a beach drinking a can of beer. "You should have brought a gun instead of a beer mate" says the bad guy.
"Nah" says Nugget, "I don't need a gun. I've got a Donk."
"A what?"
"A Donk" says Donk from behind him before putting his lights out.
I don't have a Donk but I don't need one. I've got a Dave. I think that summarises everything I could ever wish to say about DV.
To those of you who haven't had the privilege of knowing DV and being able to chat to him whenever you want I'll tell you a bit about him. I can honestly say with hand on heart I've never had a conversation with Dave I haven't come away from having learned something totally new or found a topic I suddenly realise I've not thought deeply enough about and have to get into it all over again.
Lord knows how we ever achieve anything sensible though. We might start off with good intentions of talking about a specific engine issue but 10 minutes later we're into particle physics or quantum theory or cosmology or whether you can make a mass driver to launch heavy items into space by drilling a hole right through a planet (that was one of Dave's mates Dusty's ideas and no it doesn't work). Then Dave will start yacking on endlessly about his race car driving exploits from time gone by and I'll have to sit there pretending I'm interested until I can steer him back to the engine topic again.
One of Dave's strengths is thinking outside the box and coming up with new ideas that no one else would ever think of. Google "polyquad" for example. A 4v head with one big and one small inlet valve and ditto for the exhausts. It gives the flow of a conventional 4v head but lots more swirl. Who the hell would ever have come up with that? Not me for sure. I tend to plod along with basic theory just optimising whatever I can but I doubt if I'll ever invent anything new nevermind patent it like Polyquad is.
It was Dave who immediately spotted the problem with my first flowbench design 20 years ago when I couldn't get the damn thing to measure accurately. I had a pressure tapping in the wrong place - stupid rookie mistake but easily solved. If it hadn't been for Dave I'd probably still be measuring flow inaccurately.
We disagree on lots of stuff though - which is probably healthy but often somewhat fraught. I think valve seats should have a width proportionate to the valve size so the geometry stays constant. Dave thinks they should always be 1.5mm wide whether the valve is 30mm or 60mm. I get where he's coming from in flow terms but then I also know what I've proved on customer's engines by cutting wider seats than most other people use. We'll probably go to our graves arguing about that one.
However, when I'm really stuck on some deeply technical and arcane engine issue and can't see the light at the end of the tunnel and no one else understands what the hell I'm banging on about I can phone Dave. He might not always have the immediate answer (although he usually does) but he'll always have something to say that'll get me thinking again and make me re-examine my ideas. It's hard to express just how valuable that's been to me over the years and how much I appreciate it.
The more I learn about engines the more I realise I still don't know. It's an infinite subject. All we ever do is scratch the surface and constantly reinvent the wheel that someone else has already done long ago but we didn't know about it. If most people knew just the stuff that Annand and Roe wrote about 50 years ago on cylinder heads they'd be much better engine builders.
Now I'm really off on one. I'm thinking about Crocodile Dundee II when the bad guys are looking for Mick and one of them comes across Nugget sitting on a box on a beach drinking a can of beer. "You should have brought a gun instead of a beer mate" says the bad guy.
"Nah" says Nugget, "I don't need a gun. I've got a Donk."
"A what?"
"A Donk" says Donk from behind him before putting his lights out.
I don't have a Donk but I don't need one. I've got a Dave. I think that summarises everything I could ever wish to say about DV.
There is no Doubt the two Daves are on a technical level far above most users here. And infinitely more than others ( ie the Golf )
The majority of people on this forum are simple DIY types. We dont have xx years of in depth experience building and tuning to a very precise level. We dont have years of flowbench or dyno experience. We have normal day jobs, often which dont involve engines or cars at all.
Of course some are involved at a more technical level, but most arent
I certainly couldnt even begin to answer your valve lift/flow question via mathematics. I did do A Level maths, and failed miserably. But it saved me from getting a job for a couple of years lol.
Mathematics at that level just bored the tits off me. Who the hell wants to prove 1=1, or 1=2 ??? It all just seemed ridiculous, and so far in life Ive never needed to know that.
In answer to the question, and it may go down better if you are drunk, I can only guess that flow increases simply because the shape of the entire flow path is always changing. It isnt a fixed hole or shape for the air to flow past.
But I'd hope it is apparent from most that having people like yourselves on the forums to help the simple diy people is appreciated.
This thread also highlights other issues though. Yes it's great in theory valve seats this shape, size, using these tools etc. But as you are all too well aware, if there is nobody local or even hundreds of miles away who can do the job to those precise specs...what are we to do ? We just have to make the best of the resources available to us. Often they are far from ideal, sometimes even crap. But that's life, we dont have our own machine shops so just have to get on with it.
The majority of people on this forum are simple DIY types. We dont have xx years of in depth experience building and tuning to a very precise level. We dont have years of flowbench or dyno experience. We have normal day jobs, often which dont involve engines or cars at all.
Of course some are involved at a more technical level, but most arent
I certainly couldnt even begin to answer your valve lift/flow question via mathematics. I did do A Level maths, and failed miserably. But it saved me from getting a job for a couple of years lol.
Mathematics at that level just bored the tits off me. Who the hell wants to prove 1=1, or 1=2 ??? It all just seemed ridiculous, and so far in life Ive never needed to know that.
In answer to the question, and it may go down better if you are drunk, I can only guess that flow increases simply because the shape of the entire flow path is always changing. It isnt a fixed hole or shape for the air to flow past.
But I'd hope it is apparent from most that having people like yourselves on the forums to help the simple diy people is appreciated.
This thread also highlights other issues though. Yes it's great in theory valve seats this shape, size, using these tools etc. But as you are all too well aware, if there is nobody local or even hundreds of miles away who can do the job to those precise specs...what are we to do ? We just have to make the best of the resources available to us. Often they are far from ideal, sometimes even crap. But that's life, we dont have our own machine shops so just have to get on with it.
It's getting silly now.Looks like I'm going to have to answer my own question. Imagine the diagram below is a valve and seat that are both horizontal and open by a small amount. Clearly no real engine has horizontal valve seats of course.
_
_
The vertical (perpendicular) gap between the valve and seat is exactly the same as the valve lift. Now look at an angled seat like in a real engine.
\
\
You can see that the perpendicular distance (the gap) between the valve and seat is much less than the valve lift. In fact at low lift it's the Lift x Cosine of the seat angle. For a 45 degree seat that's only 0.707 x the valve lift so a valve that's 1mm open will have a seat gap of only 0.707 mm. For a 30 degree seat the gap is much bigger. Cosine 30 = 0.866 so the 1 mm open valve will have a seat gap of 0.866 mm. That's 22% more than the 45 degree seat which is why 30 degree seats flow so much more air at low lifts.
At higher valve lifts the situation changes.
\
\
Now the seat gap is the distance from the inner edge of the seat on the valve above to the outer edge of the seat in the head below it. If you imagine drawing that line in it forms one side of a triangle where the bottom side is the seat in the head and the right hand side is the valve lift. Because we know the length of two sides of that triangle plus one of the angles we can solve the equation using the cosine rule. I won't go into details.
However we can already see that the valve gap depends on both the seat width and seat angle as well as the valve lift. The shallower the seat angle and the narrower the seat width the bigger the gap will be. Imagine a seat of zero width.
.
.
The seat gap must always be the same as the valve lift. There is no angle with a seat of zero width of course. What sort of numbers do real world seats generate though? I've already given the numbers at low lift. At higher lift, let's say the 1/2" lift of a race cam in the sort of engines most of us deal with a 2mm wide 45 degree seat will still only have a seat gap of 90% of the valve lift i.e 450 thou. A 30 degree seat will do a bit better at 93% but it's lost most of the huge advantage it had over the 45 degree seat at low lifts.
What if we narrow the seat width? A 1.5 mm wide 45 degree seat at 500 thou lift will have a gap of 92% of the lift or 460 thou. That's just over 2% better than the 2mm seat so we ought to pick up just a smidgeon more high lift flow.
However we'll probably lose some low lift flow and also the valve head will run hotter because it can't dissipate its heat so effectively. When the valve heads run hot they heat up the incoming charge and reduce cylinder filling as well as increasing the tendency to detonation.
So where does the best compromise lie? Well that depends on how often you want to rebuild your engine. I use seat widths of 4.5% of the inlet valve diameter on most road and mild competition engines because that will give you OE road engine seat life (100,000 miles plus) and still be within a percent or two (or three) of optimum flow and power. For very high power race engines with high lift cams that are rebuilt more often I might come down a tad to 4% of the valve diameter but no lower. If you go narrower than that then my opinion is that poor heat dissipation and loss of low lift flow mean any gain in high lift flow cancels out. DV might disagree with his 1.5mm wide seats on big block Chevies but we'll only ever find out if we do a dyno shootout on otherwise identical engines where of course I'll kick his arse.
Be aware though we're only talking tiny changes in bhp here. If you have a well ported head with nice 3 angled (or more angles) seats then fretting about the seat width or making them too narrow is only involving the last possible 1 or 2 percent of what it's possible to achieve. For most people a long service life will far outweigh the possible extra couple of bhp they can't even feel with narrow valve seats that wear out in no time flat and of course then lose you more than the power gain they had when they were brand new.
_
_
The vertical (perpendicular) gap between the valve and seat is exactly the same as the valve lift. Now look at an angled seat like in a real engine.
\
\
You can see that the perpendicular distance (the gap) between the valve and seat is much less than the valve lift. In fact at low lift it's the Lift x Cosine of the seat angle. For a 45 degree seat that's only 0.707 x the valve lift so a valve that's 1mm open will have a seat gap of only 0.707 mm. For a 30 degree seat the gap is much bigger. Cosine 30 = 0.866 so the 1 mm open valve will have a seat gap of 0.866 mm. That's 22% more than the 45 degree seat which is why 30 degree seats flow so much more air at low lifts.
At higher valve lifts the situation changes.
\
\
Now the seat gap is the distance from the inner edge of the seat on the valve above to the outer edge of the seat in the head below it. If you imagine drawing that line in it forms one side of a triangle where the bottom side is the seat in the head and the right hand side is the valve lift. Because we know the length of two sides of that triangle plus one of the angles we can solve the equation using the cosine rule. I won't go into details.
However we can already see that the valve gap depends on both the seat width and seat angle as well as the valve lift. The shallower the seat angle and the narrower the seat width the bigger the gap will be. Imagine a seat of zero width.
.
.
The seat gap must always be the same as the valve lift. There is no angle with a seat of zero width of course. What sort of numbers do real world seats generate though? I've already given the numbers at low lift. At higher lift, let's say the 1/2" lift of a race cam in the sort of engines most of us deal with a 2mm wide 45 degree seat will still only have a seat gap of 90% of the valve lift i.e 450 thou. A 30 degree seat will do a bit better at 93% but it's lost most of the huge advantage it had over the 45 degree seat at low lifts.
What if we narrow the seat width? A 1.5 mm wide 45 degree seat at 500 thou lift will have a gap of 92% of the lift or 460 thou. That's just over 2% better than the 2mm seat so we ought to pick up just a smidgeon more high lift flow.
However we'll probably lose some low lift flow and also the valve head will run hotter because it can't dissipate its heat so effectively. When the valve heads run hot they heat up the incoming charge and reduce cylinder filling as well as increasing the tendency to detonation.
So where does the best compromise lie? Well that depends on how often you want to rebuild your engine. I use seat widths of 4.5% of the inlet valve diameter on most road and mild competition engines because that will give you OE road engine seat life (100,000 miles plus) and still be within a percent or two (or three) of optimum flow and power. For very high power race engines with high lift cams that are rebuilt more often I might come down a tad to 4% of the valve diameter but no lower. If you go narrower than that then my opinion is that poor heat dissipation and loss of low lift flow mean any gain in high lift flow cancels out. DV might disagree with his 1.5mm wide seats on big block Chevies but we'll only ever find out if we do a dyno shootout on otherwise identical engines where of course I'll kick his arse.
Be aware though we're only talking tiny changes in bhp here. If you have a well ported head with nice 3 angled (or more angles) seats then fretting about the seat width or making them too narrow is only involving the last possible 1 or 2 percent of what it's possible to achieve. For most people a long service life will far outweigh the possible extra couple of bhp they can't even feel with narrow valve seats that wear out in no time flat and of course then lose you more than the power gain they had when they were brand new.
What effect does valve and seat materials have on how narrow you can go on the seat?
With materials such as inconel and sodium filled exhaust valves and CuBe valve seats being used in motorsport, is there way of gauging how much you can reduce the seat.
Sodium filled exhaust valves have been fitted in production engines of 100bhp/lt (BMW M3/M5 and Sierra Cosworths) since the mid 80's.
Steve
With materials such as inconel and sodium filled exhaust valves and CuBe valve seats being used in motorsport, is there way of gauging how much you can reduce the seat.
Sodium filled exhaust valves have been fitted in production engines of 100bhp/lt (BMW M3/M5 and Sierra Cosworths) since the mid 80's.
Steve
Stevieturbo does raise a fair point about having the knowledge is different to having the means to apply it. Us amateurs are at the mercy of the folks who provide the services.
I was lucky enough (if you can call it that) to not be tripped up by some valves I purchased recently. They were from a respected German manufacturer and came at a premium price (although less than the stock items, which are a silly price!!).
Working for a large engineering company, I have some useful equipment at my disposal so I decided to check the dimensions of the "high quality" valves on a shadowgraph (google it!). Suffice to say, the variation in seat thickness ranged from 0.988 to 1.252mm on the exhaust side. The edge thickness' was of a similar tolerance and even head diameter (In 38mm, Ex 32mm) had a significant tolerance. When I looked at the figures I did some sums (cosine ;-) to see if I could have the narrower seats reground and still retain the edge thickness. Nope! I felt that the edge thickness would have been too thin, thinner in fact than the thinnest "as supplied" valve. So basically they were unusable for me.
I was astounded that a company of such a slick (Rhymes with...) reputation would turn out such trash.
I turned back to new original equipment valves (BMW sodium filled mucho ££) and when they arrived I did the same checks. Don't remember the numbers, but they were very much in the ball park. In fact IIRC, I gave up after 5 or 6 because I was seeing no where near the tolerances as the after market valves.
Anyway, what sort of edge thickness on the valves should we be looking at? The BMW valves were quite chunky in this department.
Steve
I was lucky enough (if you can call it that) to not be tripped up by some valves I purchased recently. They were from a respected German manufacturer and came at a premium price (although less than the stock items, which are a silly price!!).
Working for a large engineering company, I have some useful equipment at my disposal so I decided to check the dimensions of the "high quality" valves on a shadowgraph (google it!). Suffice to say, the variation in seat thickness ranged from 0.988 to 1.252mm on the exhaust side. The edge thickness' was of a similar tolerance and even head diameter (In 38mm, Ex 32mm) had a significant tolerance. When I looked at the figures I did some sums (cosine ;-) to see if I could have the narrower seats reground and still retain the edge thickness. Nope! I felt that the edge thickness would have been too thin, thinner in fact than the thinnest "as supplied" valve. So basically they were unusable for me.
I was astounded that a company of such a slick (Rhymes with...) reputation would turn out such trash.
I turned back to new original equipment valves (BMW sodium filled mucho ££) and when they arrived I did the same checks. Don't remember the numbers, but they were very much in the ball park. In fact IIRC, I gave up after 5 or 6 because I was seeing no where near the tolerances as the after market valves.
Anyway, what sort of edge thickness on the valves should we be looking at? The BMW valves were quite chunky in this department.
Steve
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