Valvepockets with an FK10 ?

[Felix/DFL]

Hi,

I have got a question about valvepockets with an FK10. I know that many drive this cam so maybe you could give me a very usefull hint.

Engine that I am building is:
78,8 x 94; FK10; CR: 10,5-11:1; deck hight 1,2 mm; Scat 1:4 forged rockers, Manley valves 42 x 37,5mm

Do I need valve pockets in the pistons?

I had the engine assembled mainly dry but the deck hight and the correct head volume aren`t machined yet so I couldn`t make a test with clay to see how close the valves get to the piston.
Other thing is that the scat rockers won`t be at my door till end of next week...
Because when I need pockets I would compensate them with a slightly less head cc`s when the heads get bored deeper.

Greetz,
Felix

[richie]

You shouldnt need them,it will depend on how much the heads are flycut down?but with 1.2mm deck and 10.5/1 compression[this would need 49cc in the head] I dont think you will need valve pockets

cheers richie,uk

[neil68]

I've run both the FK8 and 86C with 10.5 CR, heads were flycut twice (50 cc chambers), ~0.060" DH and still had just over 0.120" valve clearance when clayed, so I'd say you'll probably be fine as well.

[Felix/DFL]

Thank you both for your good advices!

At what valve clearance would you recomend pockets? I read about 0,09"...

And another thing (maybe for the next engine) Did anyone tryed out the method of cutting pockets like it is adviced in the B.Fischer book?
The big advantage would be that the pockets are exactly at the point and inthe the angle where you need them.

Greetz!

[drgouk]

My 10:1 2332cc FK10 motor did not need valve pockets, Around .570" and from memory it had over .100" Piston to valve clearence at TDC over what it what it was opening.

[Jim Ratto]

I think as time has gone on and motors have gotten bigger, cc wise, the need for very close deck heights for increased CR has diminished, lessening the need to notch.
Don't foget: cam timing can affect piston-to-valve clerance too (meaning advance or retard).