I have access to a valve grinder at school so I can grind my valves for free! My question is what is the stock angle of the valves and what other 2 angles should I use to do a 3 angle job.

 

Typically you'll do a 60deg cut to clean up the throat, then a 45 deg cut to create the surface which the valve will seal on with a .050 margin (meaning the valve and seat will touch all the way around on a .050" wide band), then you'll cut a 30deg top cut also watching to make sure you still have a .050 margin with the vlave face. You can then cut the vlaves surface to 45 deg.

Some people will differ on the angles. Some will use a 50deg angle on the valve face and seat for the sealing surface but you'll run into longevity issues with steeper or shallower sealing angles.

Other things to do would be to back cut the vlaves at a steeper angle, and if you get really into it you could try a 5 or 7 angle cut on the seat.

Exhaust valves sometimes like to have the edge of the vlave rounded to smooth the air as it wraps around the edges of the valve but other modifications may be necessart to see the benifits.

 

Off the topic here, and no intent to hijack, but what kind of gains would you expect to see from a 3-angle valve job? Also, how much would this normally cost?

 

thanks.