this may be a dumb question, but has anyone ever installed new valves and just lapped the valves by hand instead of having a machine shop cut them. if the seats aren't pitted and you get the proper valve seat width after lapping for proper valve cooling, what's the difference? i did it on a chevy 350 80,000 miles ago and still have good compression on all the cylinders after beating the hell out of that old blazer. and is a three angle valve job necessary if you have undercut stems?

i may have found the answer to my own question. a friend of mine who is a machinest that builds and races cars told me that the seats are 45 degrees. the valves are usually 46 degrees. if the seats are good, lapping the valves by hand is fine. a shop usually touches up the seats back to 45 degrees if needed or replaces them. sound right?.................. i stumped everybody?

If you've just spent money on new valves, why not spend the extra $100 to get the valve job. Its just not worth not doing.

Be sure to verify the valve guide clearance. If you're having the valve guides replaced you'll need to grind the seats.

thanks for your input. i'm guessing that if you put in new guides, the reson to regrind the seats is because the new guides are the guide for the seat grinder and the face to seat angle may be off if the new guide isn't on the exact centerline as the old guide?