Engine/Transmission (1994 - 1998) 3-angle valve grind specs?

[JGK]

I posted this over in the competition forum but got a response from only 1 person. Maybe I'll have some luck here.



My searches in the forums find several posts where a 3-angle valve grind is recommended for performance. But no where have I found specifics on the how the grinding should be done. Can anyone provide the specs? This is for a 12-valve head.



I know that a 45° face and seat are typically used on both the intake and exhaust on gas engines, but the 12-valve CTD uses a 30° face and seat angle on the intake. Is that maintained on a 3-angle performance grind or is that changed?



The other 2 angles on a gas engine are generally about 15° on the chamber side and 60° on the port side. What about the angles on the CTD? Also, about a 35° back cut is sometimes done on the back side of the intake valve head on a gas engine, but no such back cut is done on the exhaust valve. Same on our CTD?



Is any grinding recommended at the edge of the valve where the face meets the margin, and if so, what angle?



All these questions are in anticipation of doing an o-ring job and as long as the head is off and getting decked, the valves will be inspected and serviced if needed. So I might as well have this done if the cost isn’t bad.



Thanks in advance.

-Jay

 

[keimmmo]

I used to work in an automotive machine shop. The basic rule for the cuts above and below the seat is to split the difference between the seat angle and the chamber or port. On the top cut you can still use 15*... it would be fine to flatten it out a little to like 10-12* if you want. The bottom cut would still work fine with a 60* cut. If you want something even better, do a 4-angle valve job and undercut the seats with a 45* followed by a 60*.



What I am telling you is just based on basic machine shop logic... not on what has been proven to flow the best on a flowbench. You might be able to get better information by calling or visiting someone who modifies the diesel heads for a living.



I would think that undercutting the valve heads much like on a gasser would also work well on a diesel... but again this is my logic, not proven knowledge.



Hope this helps.



Steve

 

[JGK]

Steve,



Yes, it does! Thank you.



Any one else that can expand on this?



-Jay