I am installing larger valves in my 350 heads but would rather not damage the existing seat. Any ideas other than be careful? Scott
I will definitely do that when I'm polishing the combustion chamber but when I'm doing the turn into the chamber that's when I run into problems. Do I have to worry allot if going with bigger valves? I will be as careful as i can....just wondering. Tape won't stick either. Scott
I went through this five or so years back and every single person said do a valve job AFTER the porting. Sure that's the right and safe way, but of course not what I wanted to do or hear. That being said, there is no fool proof way and all requires a measure of carefulness. I personally wrapped the cutting bit's shank in two layers of duct tape, and then did likewise for the seats. Good quality duct tape, some brake clean to get the seats nice, clean and dry for the duct tape to stick too (1/4" wide strips about an inch long). A couple times I knicked the duct tape if the die grinder jumped/chattered on me or for what ever reason, but over all it protected the seats pretty good as I never went forcefully into them so the two layers of duct tape took all the brunt pretty well. I would brake clean and apply new duct tape everytime I knicked it. That's the "best" I got for a suggestion. A valve job after the fact is always the recommended way, but backyard porting isn't done with hundreds of dollars worth of work.
Scott, were the valve seats cut for the larger valves yet? If not I wouldn't worry too much about nicking the existing seat since it'll have to be cut out anyway. One of my grinders has a nut that has nicked my work. I slipped some rubber tubing over it to keep it from damaging anything. My best advice is to pay attention and keep two hands on it to keep it under control.
^^^ Yes, that damned nut on the die grinder, that's what tagged the seats more for me too now that you mention it. I was thinking as I typed my first post "I know I wasn't that sloppy that I was tagging the seats with the cutting edge, but I do remember replacing the duct tape on a regular basis". I never bought the long shank cutting bit, just used the standard one to the best of my ability and it was that dang holding nut that kept giving me trouble.
Thank you Walt and The SilverBuick (hope that isn't your real name 'cause it doesn't roll of the tongue easily ) Will definitely do both! It is that cotton pickin' nut that's doing me in too. Although a longer shank bit wouldn't hurt either. Thanks again I will continue grinding and polishing. Scott
