pdxmotorhead

Not wanting to de-rail anybody else thread so I thought I'd ask as a stand alone topic..

Valve lapping , I haven't done it for 20+ years. Machine and go..
I know quite a few top end engine builders, none of them lap valves.
Based on leak down testing and dyno work most of them claim it hurts power more often than helps on a new valve grind. More often than not its a net zero gain.

I was taught to oil the seat, slip the valve in and simply snap it to the seat a couple times to leave a line on the valve and seat just so you could tell your grind matched..

What says the current folks wisdom ,, to lap or not to lap that is the question..

01ssreda4

iTrader: (96)

This is a good subject to talk about. I think there will be 3 main responses. One is people who dont know and have never done it, Two is the backyard mechanic that will do it by hand or drill, and Three is an over technical machinist version of the answer. I dont think any of the 3 is wrong, just different ways to view it.

KCS

iTrader: (20)

I was taught to use lapping to check the seat after the valve job is cut. We apply machinists dye, like Dykem, and then look at the ring left after the lapping. If the valve job is not concentric or the angles in the seat and the valve do not match, it will show. Below is an example: