5 angle valve seats + & -

[steve_k]

right then folks time for a bit of advise please.

after reading the thread by hairyscreech about the 2.8l stroker's & porting & polishing & gas flowing the head (which i already know about as the head on my b25 already has it) i was wondering about 5 angle valve seats after seeing it in a thread on here (can't remember the title or i would search for it).

what i would like to know is what advantages does it offer over 3 angle valve seats? (which my 885 head also has)

so does any body know? have any pictures?

come on surely someone must know??

[Gunni]

There are gains to be had.

of course a intake port shouldn´t be polished.

[steve_k]

There are gains to be had.

of course a intake port shouldn´t be polished.

cheers gunni i thought you might answer.

so what kind of gains are there??

& yes i know what you mean about an intake port shouldn't be polished.

[Gunni]

It´s all relative.

How good is the port attachment so far that this will be further use, if the port is bad in front this will not help as much as if it´s good.

It´s hard to point at a flow gain number.

[gareth]

from my days playing with 205GTi's and the like, they respond very well to a 5 angle vlave job. in fact most owners claim about 10-15bhp increase on the 1.9 16V Mi16 engine from this alone

They are however known for being very good in the port-shape department but have french quality finishing to the valve seats, ie very agricultural!

[steve_k]

cheers fella's

i only ask as i've been talking to a mate of mine who does a lot of work for me when it cones to rebuilding m20b20/b25 heads & it is/was something both me & him are keen to look into.

[e301988325i]

right then folks time for a bit of advise please.

after reading the thread by hairyscreech about the 2.8l stroker's & porting & polishing & gas flowing the head (which i already know about as the head on my b25 already has it) i was wondering about 5 angle valve seats after seeing it in a thread on here (can't remember the title or i would search for it).

what i would like to know is what advantages does it offer over 3 angle valve seats? (which my 885 head also has)

so does any body know? have any pictures?

come on surely someone must know??

Who IIRC said there wasn't enough space for to make more than 3 angle seats work. . .

[HairyScreech]

as per usual i cant be cast iron on things, but....

the standard seat is a 90/45 job and is about 2mm wide, this can be reduced to about 1.3mm and still be thermally safe, a 3 angle will probably be a 60/45/30 which is good, but i have heard it suggested that a 70/45/30 may be better.

i know the Kawasaki boys use a 75/65/45/30 cut and that gives a little more on that particular head.

as for a further 20 or 15 degree cut on the far outside of the seat id say its a waste of time for a road car, your talking about a cut thats going to be less than 0.5mm wide. and your going to have to pay for 12 of them. so its your choice.

by the end of this year i will have CFD information on the various seat angles.

but for now ill say its not worth going from a 3 angle to a 4 or 5 angle just for the sake of it, anything you get cut will probably be a shot in the dark and may make things worse.

if you have normal 90/45/0 seats then a 60(70)/45/30 or 75/65/45/30 will show large improvements as there is quite a bit of flow detachment after about 9mm lift.

edit - ill actually be able to tell you the idea surface finish for the ports as well hopefully.

[Gunni]

I have it from the highest of authorities that a new 400grid paper is the perfect port finish.
This is straight from F1 engine building

[HairyScreech]

well the generally accepted method is using a split rod with a wrap of emery cloth in it.

i dont have any of the sugested finishes to hand, but what i can do with the CFD programs is tell them the surface finnish in RA, which will allow me to hone in on the best finish for these heads.

its all work to come at the mo though.

re my thread, iv got a load of info on the piston and rod forces to put up soon.

[punko]

why angle the flow of air at the valve rather than past it?

[Gunni]

That is not what is being proposed at all.

with multi angle valve jobs you have a better chance of making the air bend around the valve seat into the head and not become turbulent in the valve seat, which causes a restriction.

[steve_k]

wow thanks for the replies folks.

i only asked as when it comes to an 885 head it all seems to be a bit of a dark art

so any/all info is gratefully received

[HairyScreech]

5 angle seat.

a good explanation of what we are on about can be found here

http://www.camarohomepage.com/project/part2.htm

[HairyScreech]

its only a dark art as the tuners in this country tend to close ranks and offer smoke and mirrors when you ask a simple question.

[steve_k]

screech cheers for that link

if you have any other info would it be possible for you to email to me? just so i can read it properly & take it all in.