Valves on a l20b w58 head

[DATSUN671]

What's a good oversize valve I can use on the w58 head or can I use the ka or z24 valve?

[datzenmike]

KA valves are smaller diameter heads. Z series have longer stems. Generally people use valves from a Z car six cylinder. No idea what ones are which.

[banzai510(hainz)]

i WOULD STIK WITH THE STOCK 1.65

 

PEOPLE PUT 1.73 280Z VSLVES BUT THE SEATS NEED TO BE INSTALLED ALSO. make sure machinist dont put them in wrong and they fall out ruining your motor

[datzenmike]

You can get a nice increase in top end flow of air by unshrouding and radiusing between valve seat and the closest  part of the cylinder wall. Going to larger width will make this tight area even more imperative.

[ggzilla]

42 mm: Stock intake valve size for W58. Same as the SSS head and L26

 

38 mm: L24, L16

 

44 mm: L28

[DATSUN671]

Is it okay if I just grind valve the oversize valve to the stock valve seat?

[datzenmike]

Nope. Seats must match the valve face diameter.

[DATSUN671]

How will I do that?

[datzenmike]

A machine shop will remove the old seats and over size the seat area. The head is machined to the same size as the seat and heated to expand it while the seat is frozen to shrink it. The seat is installed and the two parts will squeezed together and hold without falling out. Now the seat is ground to align with the valve guide and valve lapped in. 

 

A larger valve will let more air in but in most cases the stock valve is more than good enough at normal RPMs.

[DATSUN671]

Is it possible to over grind a valve? Cuz I did a valve grind and the more I grind the more it leak faster. What are my options?

 

Thanks for the help

[datzenmike]

Valve grinding is done on a special machine. Valve lapping is often done by hand using a compound of oil and fine carborundum powder. The purpose is to finely polish the valve face and seat for a good seal.

[ggzilla]

Is it possible to over grind a valve? Cuz I did a valve grind and the more I grind the more it leak faster. What are my options?

 

Thanks for the help

Definitely you can overgrind. Datsun used a three-angle valve job from the factory so the mating area is only about 1/16" wide. It takes careful grinding to prevent that from being messed up.

 

If it id leaking now, your option is to replace the seat and the valve. Use machinists bluing to find the actual matching pattern and go from there.