Valve seat cutting??? 46 degree seats?

spook · Post by **spook** » Mon Sep 21, 2009 7:31 pm

I would like to get members thoughts on cutting valve seats to 46 degrees as explained on page 4 of this PDF. Cheers

http://lib.store.yahoo.net/lib/yhst-580 ... manual.pdf

sickle44 · Post by **sickle44** » Tue Sep 22, 2009 10:42 am

I didn't read the PDF spook, but here's my

on valve cutting. I've always been told that the five angle cut is the most desirable. It will quickly become a nice rounded edge because there are so many different edges on the cut. Eventually it will seat to an excellent seal faster and tighter than any of the other cutting styles? Hope that helps.

Yoniboi · Post by **Yoniboi** » Tue Sep 22, 2009 1:26 pm

The only problem with a five angle cut is that there are very very few people in the world with a machine that's capable of doing 5 angle on valves as small as the EXUPs.

As far as I know the only machine capable of doing 5 angle cuts on valves like ours is the SERDI 5.0, and these are the only guys who've got one:

* VANCE & HINES
* CARL'S SPEED SHOP
* RENAULT SPORT
* ALPINA TUNING
* AMG MOTORENBAU
* BMW MOTORSPORT
* ALFA ROMEO CORSE
* CAGIVA
* DUCATI
* FERRARI F1
* FIAT ALFA ROME0
* LAMBORGHINI FI
* MOTO GUZZI MOTORS
* MOTO LAVERDA

SOME 0.E.M. AND PRODUCTION MANUFACTURERS

* BMW AG
* CATERPILLAR
* CUMMINS
* DAF
* FORD
* MERCEDES BENZ
* PORSCHE AG

SERDI s5.0 USERS

* FORD
* CUMMINS
* UNIBORING
* PRICE ENGINEERING
* JOSEPH BROTHERS
* GEM ENGINES
* HM ENGINES
* MUSTE
* AUSMA
* ALLUMAARSE MOTORENREVISLE
* SCHMITZ & KRIEGER
* CYLINDER HEAD SHOP

I went with the last guy on the list, who charged me 700 pounds sterling, did a sterling job on cutting the valve seats, re-lining 8 valve guides (exhaust), and then went and scratched a bloody great big scratch on the gasket seat and claimed I'd done it unpacking.... so I wouldn't recommend him. Christ, it only cost 20 pounds to put 'right' locally (took 0.5mm off the cylinder head to sort it) and he refused to sort it out, so no goodwill there then.

Anyway, yeah, the arguments for 5 angle are good, and I've got to admit that the pulls as well as the Spondon which has a TTS gas flowed head.

John

hotcam · Post by **hotcam** » Wed Sep 23, 2009 11:47 pm

I understand the idea, and can see no problems with the idea of
an interference fit. But the conical shape of the seating area
means that it's an interference fit anyhow.

I am concerned that on valves as small as ours, the valve head, and
valve seat, may not flex enough to cause normal contact across
the whole seating area if a 46-45 cut were used.

If the valve only contacts the seat on that narrow line, then heat
is restricted from flowing away from the valve head to the valve
seat, leaving the valve insufficiently cooled. This is a very important
part of cooling the valve (says Phil Irving's "Tuning for Speed" and
Yamaha's "OW01 Race Tuning Manual"). In fact, Yamaha recommended
setting the valve lash loose on the racing motors, to allow the valves
a few more microseconds on the seat for cooling purposes.

I can see that on larger valves, particularly cooler-running engines where
heat is not such a factor, it could be beneficial...

With a large flexible valve a 45-45 cut could allow the valve
to flex in such a way that
the seat and valve face is actually exposed to the combustion,
causing accelerated seat and valve face wear, and depositing of
combustion byproducts.

Here's a little picture to show what I mean:

If we want to use the interference/offset-angles cut on valves this
size, it might be necessary to use a 45.5degree or similar. I'd need
some pretty hefty FEM software and detailed engineering specs on engine
stresses and material specifications to figure it out for sure.

This is all just based on thinking processes, I am not an experienced valve
designer even though I have a little training in related areas.

hotcam · Post by **hotcam** » Wed Sep 23, 2009 11:51 pm

As for 5-angle cuts, they're good to smooth the gas flow in and out
over the sharp corners of the cuts, although they don't affect the seating
mechanics of the valve at all.

Do y'all think that a very careful precise owner could spend the time
to do a decent 5-angle cut with a hand cutter, rather than using
a machine? I'd like to try it one day (perhaps NOT on something
that has 20 valves though!!!)

spook · Post by **spook** » Thu Sep 24, 2009 12:11 am

Just to save anyone actually reading the pdf relevant to the topic, here is a screen shot of what I'm talking about. I think you may have it backwards in your drawing Cam, the seat would be 46 degrees while the valve remains at 45. The narrower the sealing point the better?

hotcam · Post by **hotcam** » Thu Sep 24, 2009 12:32 am

Just to save anyone actually reading the pdf relevant to the topic, here is a screen shot of what I'm talking about. I think you may have it backwards in your drawing Cam, the seat would be 46 degrees while the valve remains at 45. The narrower the sealing point the better?

I read the thing and am quite interested in an armchair sort of way.

What I am trying to say is, if the valve flexes, a 45-45 cut might degrade
to a 44-45 seal (shown in my picture). They are trying to
anticipate and counteract the potential flex and poor seating that
I have drawn in the picture.

If the valve has a 46-45 cut(as in your PDF), and then it flexes,
it might degrade to a 45-45 seal which is a good seal. Do you know
what I am trying to say?

I think our problem with doing this on a FZ/FZR is that we don't know
how much (if any) our valve will flex. I think it won't flex much as it
is a very small diameter and quite deep for its diameter...
Unlike these which are more likely to flex as the shape of the head is
flat and shallow:

So do we cut 46degrees? 47degrees? 45.5degrees? 45.1degrees?
Do we hope that any imprecision by us is fixed when the seats
compress due to the impacts of running-in the motor?
Or do we cut them matching 45-45, and hope they don't flex appreciably?

spook · Post by **spook** » Thu Sep 24, 2009 1:37 am

Just say for example they don't flex?

sickle44 · Post by **sickle44** » Thu Sep 24, 2009 2:01 am

Hey Cam,

To answer all your questions, I think you might have too much time on your hands?? Sorry dude, just kidding, somewhat, if I had the time, skill, and tools I would definitely try the interference angle cut on something like my scooter or an a/c two valve twin. If you screw something up, it won't cost you too much, 4*35, however, bugger up an exup or other high zute stuff and, well, do the math right; 16*35, or 20*35. What's that, you say?
You'd like Titanium valves, LOl,
oh well...... 20*???........

My very first bike was a seca 750, two valve a-o/c motor that was bullet proof. If only Yamaha could have put some real fuel mixers on it and a chain. Anyways my point is this, and you even eluded to it yourself, rather than tackle a higher-performance 20-valve machine, why not try hot rodding something much easier and then get adventurous.

Lastly,

You had made a comparison to racing machines which IMO, unless you are racing the machine you are discussing, don't bother comparing with what a racing machine does. I'm sure you know why I'm suggesting this, so I won't even bother saying, but I will say, apples to apples and oranges to oranges.

sickle44 · Post by **sickle44** » Thu Sep 24, 2009 2:05 am

Ooops,

Sorry,

One more thing, I've also heard that the 5 angle cut can be undesirable as having so many angles, the valve may have the tendency to round out sooner, and you end up with a much larger contact surface which I just learned, or remembered, from earlier comments is undesirable. That being said, I've heard there is possilby more merrit to a 3-angle grind opposed to the 5-angle, not to play with your head or anything.

Cheers, man, Nite!

spook · Post by **spook** » Thu Sep 24, 2009 2:22 am

Lol...

I'm not going to bother with 5 cuts either, it is desirable however, to keep the valve contact area in a narrow band, hence at least a three cut seat. Three cuts are about combustion gas seal, 5 are about gas flow.

The reason I raised the question is because I think it is interesting and hadn't heard of this concept before. Sort of makes sense in regards to a good seal that would only potentially get better as the valve recedes?

Where's Dr Ozzy when you need him? Probably hiding under a McLaren?

hotcam · Post by **hotcam** » Thu Sep 24, 2009 6:42 am

Just say for example they don't flex?

Then I'd be tempted to go with the 45-45 cut, or as close as you can
get, erring on the side of 46-45 that they recommend. On valves this
small I don't even know if you could measure the difference between
a 45 and a 46 cut anyhow. It's probably all microscopic and makes
no difference... ... anyone?

too much time on your hands

Sometimes...

If you screw something up, it won't cost you too much,...hot rodding something much easier

Exactly, I was thinking (daydreaming?) of how simple it would be to
work on a single- cylinder supermotard.

unless you are racing the machine you are discussing, ...I'm sure you know why I'm suggesting this

Spook is racing his FZ, which is the bike I thought we were
talking about.
Besides,

if you keep making
dangerous suggestions like that I'm gonna have to find out what it
will take to put my 1000exup into the post-modern or
whatever the category is...

Now back to your regular programming :cool

One more thing, I've also heard that the 5 angle cut can be undesirable as having so many angles, the valve may have the tendency to round out sooner, and you end up with a much larger contact surface which I just learned, or remembered, from earlier comments is undesirable.

Yes I think you are right (according to Phil Irving again), an overly
large contact area is less desirable due to something-or-other
about the gas flow at small valve openings.

spook · Post by **spook** » Thu Sep 24, 2009 8:00 am

Cam, I have a good sized bin... I will have your fzr looking like a whippet in no time. All cutting such as we have been talking about you would think is done by hand... Hmmm but i do have an angle grinder.... and yes they make a 46 degree cutter.