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Hi all, I picked up a set of 243's a while back and did the check with water in the chambers and compressed air in the ports, shown in pics below. Nothing major but some tiny little bubbles when I got the compressor wand right up against the seam. So I figured I would lap them. I used the drill method and went nice and gentle, and all seemed well, they all had a nice clean surface. Will attach pictures. After lapping and installing all of them the leaks all seem much worse. How could this be? Some guys just put water in the chambers and see if they leak, but isn't compressed air a better test cause it gives some pressure? Any info is appreciated.
Looks like you used beach sand as the grinding material? The TRW stuff perhaps?
Also looks like the seat isn't perpendicular to the guide. Or maybe there's tolerance in the guide. Can you clear it up by rocking the valve stem? If it's that, the pressure from the spring will tend to center it.
Yup, that's the same kind of thing as I was talking about. WWWWWWAAAAAAAAAAAYYYYYYYYYYY too coarse of a grit.
That stuff is about 80 grit. You need about the medium fine or the fine. https://www.newmantools.com/clover.htm I think the stuff I have is about the 240 grit on this page, maybe the 280 or 320. I'm too lazy to dig it up and look. MUCH finer than the other though, which I also keep some of around for other uses.
You rock the valve stem, without the spring installed, by grabbing it, and ... rocking it. See how far it moves. Ideally it should be no more than .004 - .005" or so at the tip, which would correspond to around .0015 - .002" of guide clearance. If the guides have very much more clearance than that then any lapping you do will have ALOT of uncertainty built in.
Those look like just stock valves anyway, probably shouldn't expect too much precision out of them.
Hmm, well on the tube it says it has 4 partice sizes in it. 120, 150, 180, 220. It also says "the 120 grit will grind down to a fine 220 grit. I've seen other people use it with no problems. It dosent make sense that it's so bad where it is completely useless to lap valves. Also I'll be installing the btr 660 spring kit, but I wanted to get all the valves sealing properly before that.
Last edited by 65gmcC10; Sep 10, 2023 at 01:24 AM.
Do what the above post says.
From some of your earlier posts you're gonna put in a somewhat rowdy cam in the engine and I'm sure the rpm's are going to be tested. Do it right the first time.
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valves leak more after lapping?? 
