How to Lap in Exhaust and Inlet Valves
Ed HughesLapping valves ensures a perfect seal and can help with running significantly. Be careful not to get stray grinding paste into valve guides.
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What we're going to do is to take a little bit of the grinding paste and pop it around the edge of the valve, like so. Smear it gently around. Now you want to try and avoid as you're working, getting this into the valve guides, because it's very, very abrasive. You may think this is completely impossible but you'd be surprised. The odd bit of it does escape from time to time.
Now I hold this special tool, which has a sucker at each end and I hold it between my hands there and I rotate the tool backwards and forwards. And occasionally I'll lift it, rotate it a bit and drop it back down. What that does is it redistributes the abrasive. All the time I'm doing this, the abrasive is being ground down. It does naturally get less and less coarse the more you grind and you'll feel that.
You'll feel it get a smoother feel. You get a smoother job as it goes on.