The Stovebolt Site Forums The Shop Area Engine Shop Valve evaluation

I have a pile of used valves. What is the general opinion of using any in a rebuild? I have done so in the past after looking them over, but have never done much in the way of measuring anything. My evaluation consists of looking at the margin, seeing if they are straight and that the face shows no sign of being out of round or burned. I haven't had much problem with them, but what is the most correct way of doing this. I would imagine using a mic on the shaft and chucking them up in a drill press or lathe to check for being bent is a start.

Bent stems are easy to identify- - - -during the regrinding process they will wobble against the grindstone and make a distinctive sound. I could tell when a student had a bent-stem valve in the grinder from halfway across the school shop just by listening to the sound the grinding machine was making. The margin will also be an uneven width if somebody insists on continuing to grind a valve with an obviously bent stem. After grinding, there should be a minimum of 1/16" margin on an intake valve or 3/32" on an exhaust. (.060" intake, .090" exhaust) . Measure the stem diameter where it enters the valve guide with a micrometer. As long as it's within .001" of original diameter, it's probably OK, but be aware that any wear at all from top to bottom will cause a slight side to side wobble in the guide, because guides must be reamed to accommodate the top of the stem for the valve to be able to be inserted into the guide. All these things were common knowledge back when real mechanics did their own machine work. Now we're dealing with the lack of knowledge created by around three generations of parts swappers who have no clue about how engine machining is done.
Jerry

I have given up asking for the guides to knurled several years ago. Lots of blank stares. Thanks, had the mic out yesterday.

Ditto for putting bronze liners in guides to recondition them. I've got all the tooling to do that, but the sleeves are getting a little hard to find. Knurling was never high on my priority list because it had a tendency to be a short term fix. The nice thing about sleeves is they can be replaced in the unlikely event they get worn.
Jerry

My valve grinders are so ancient they have the attachment for cutting flathead Ford stems to the right length for non adjustable lifters and another grinds a crown on the bottom of a used lifter. My favorite is a Tobin-Arp that grinds on the side of the stone so a worn out stone cuts at the same speed as a new one. One not used since circle track days is a Black and Decker dry grinder that one had to go very slow to prevent heat but left an absolute mirror finish. Lapping pattern showed instantly. We used all intake valves cut back to exhaust dimensions as they would bend but not break. Probably wouldn't be a good idea on non-alcohol engines. Used many used valves that measured within specs.

You'd better explain "lapping", Evan- - - - -some of these young sprouts have never heard that term! I've still got a few tins of Clover compound, but I've been using Prussian Blue to check seat width instead of lapping valves for the past 20 years or so. Try filling a combustion chamber with alcohol sometime and see which valves leak- - - -the lapped ones don't seal as well as ones with the ground finish only. Another slick trick is to use vacuum on the intake and exhaust ports to check for a good valve/seat seal.
Jerry

Mystery solved! Forgot to question one of the premier engine builders in the Dallas area when I picked up the short block for my 46 Ford coupe. The blue stuff now makes sense.

[img]https://i.postimg.cc/5jN5zmf3/flathead-short-block-001.jpg[/img]