Titanium valves

[brewsy]

Hi All,
First question so please be gentle 

Im building my parts list on my imaginary (at the moment) 1300cc turbo motor.
Before anybody asks why in the world I just want to be different...
Idea is for 1285 via 77mm bore and 69mm stock length stroke, lots of revs and a turbo with the aim to be 200+ WHP.
Johannes (JPM) seems to be running super high revs and IIRC is using a stock crank(?).
I'm aiming to make it super short by using modern 'short' pistons either motorcycle type slippers or (new) Mini pistons as the Prince engine has a 77mm bore.

Anyway back to the question:
Light weight but strong valves and valve train will be needed for high speed control.
Stock VW valves are 8mm stem correct? Modern engines seem to be using 7mm stems.
Looking online I can get an amazing deal on a set of Ti inlet valves using a 35mm head and 5mm stem diameter, they are even within 2mm of same length of a stock VW valve.
From the online research Ive done that is a size commonly used on motorcyles.

Was thinking that with steel lash cap and/or machining of rocker shaft stands overall valve length will be a non issue. Am I wrong?
With a 5mm shaft and being made of Ti that would give an extra weight saving (probably fairly small but a saving nonetheless) and being so narrow it also would help flow somewhat.

Would there be any good reason why I shouldn't buy these and use them in this motor?

Cheers
Marc

[modnrod]

I have mocked up a set of similar valves for a similar reason........coz I can, and I'm not scared!  

Anyway, mine are 35mm, 6.6mm stem and 2mm shorter than Type 1 stock. They weigh in at 52g each in SI stainless version. I got the matching bronze guides as well, but in the box I also have the matching set of super lightweight beehive springs, retainers and collets.
I have managed to bring the measured  valvetrain weight for the lot from 130g or so for stock components down to about 80g total.
 

The problem I have run into is that my retainers with the stock Type 1 valve seat depth in the head will only allow for an installed height of 1.45", which will only give me a maximum safe lift within bind limits of .360" at the valve, so I haven't used them all yet until I can find some retainers that will allow the spring to extend to their correct length.
That may be something to check before buying if possible with your selected components.

Trying something new-to-you as a science experiment to keep yourself amused is a great reason to do something different.
Have fun I rekn.

[brewsy]

The problem I have run into is that my retainers with the stock Type 1 valve seat depth in the head will only allow for an installed height of 1.45", which will only give me a maximum safe lift within bind limits of .360" at the valve, so I haven't used them all yet until I can find some retainers that will allow the spring to extend to their correct length.
That may be something to check before buying if possible with your selected components.

Cheers Mod,
With an answer like that and the price being so good I think I'll do it anyway. Worst case I end up with some desk ornaments I can give my mates!!

I havent checked safe lift as at the moment I have nothing to check it against!! These valves will be the 1st component that I'll actually have bought!! 

May I ask if you had considered just machining down the spring seat to get some more installed spring length? OR is that not a wise thing on an air cooled head?

Ta
Marc

[modnrod]

You have to be careful with the spring seat depth, cut them too deep and they can crack through into the port.
I'm not sure of the thickness exactly but I have ported through into the seat in the past (over-exuberance! LOL!) and from memory it didn't take much.
I don't know how much room I've got there, but haven't progressed these parts much yet due to other factors anyway, I will get something organised when I get the time.