I am attempting to measure the valve stem to guide clearance and would like some guidance on this. I have a dial gauge and a magnetic base. With the valve open only 1/2 way, I move the gauge feeler to touch the valve head, then a little farther so the gauge is within range. Then by pushing the valve head I can see the deflection. I noticed that if I push harder, the clearance is larger by 2-3 thousands. I suspect the valve is bending slightly and this larger clearance is not correct?. I am getting measurements of between 4 and 7 thousands. Only one valve is 7, the others are closer to 4 or 5. The 7 valve stem has about 2 thou wear on it, where the others do not. I could replace this valve to get it within the range of the others. Ideas? Thanks Mike
I've heard about a rough test if the valve guide clearance is OK or not is to hold the finger tight under the valve guide with the valve loose in the guide, lightly oiled. Pull the valve straight up - if you hear a distinct "plop", the guide and valve is good enough, no plop means it's too much clearance
This operation should be performed with a small bore gauge and a micrometer. With the setup you're attempting, there's a lot of geometry to take into account, not to mention general voodoo also coming into play.
Mike, you need to have the indicator are straight down to get a good reading. The way you have is WAY off. You are dealing with an arc your way. Scott
When adjusting valve clearance be sure to have all springs in place except the one on the valve you are measuring. I can't tell from your photo but I am guessing you have all springs removed. Not the way to do it because there will inevitably be a small amount of slop between the bearing shells and the bore and the cam journals and bearings. With the springs in place you are measuring the lash how it will be when the car is running. That's the clearance you want. You'd be surprised at the difference.
Roger, I tried your idea. I didn't hear a plop, but with my hearing, it could have happened. If a tree fell in the forest and I was facing the wrong way, did it actually fall?
Walter, I don't have a small bore gauge, so it's this or?
Scott, I understand the cosine error. I tried to straighten the gauge out some more and I didn't see much difference.
Richard, I don't understand. Am I confusing valve lash with valve stem clearance? Are you saying the when the valve lash is checked, having the springs in place will load the camshaft some and make for different lash readings?
Mike - You've started an interesting discussion here. I'm sure not the one to offer you much help as far as a direct answer to your question of how to measure "valve stem to guide clearance", but that problem gives me an idea that may or may not make any sense:
For a skilled machinist or mechanic with proper (but expensive) measuring tools, my "idea" would probably seem silly. But for a "shade tree mechanic" like me, how about this:
Many of us have (or have access to) a small lathe and a micrometer. It wouldn't think it would be too hard to make a set of "go-no-go" pin gauges which vary in diameter from "go" to "no go" by maybe .002" increments. That way, us "shade tree mechanics" could maybe get a pretty good idea of guide diameter by actual "feel" using the various diameter home-made gauges. Does that make sense? Only thing is, you wouldn't be able to determine any out-of-round of the guides.
Again, just sort of "thinking out loud" here,.....FWIW,......harold
I don't know how hard you were pushing but I doubt the valve stem was deflecting much. You may have just been pushing oil out of the measurement. If you want accurate measurements on clearance, you need the right tools; Otherwise, you might as well be using a ruler.
Measure the bore then measure the stem at it's travel point in the guide. The difference is clearance.
While you're checking the bore, you can check to see if it's out of round by measuring in several places. If the cam follower is worn and valve is not turning, the bore will wear into an oval.
IMHO your measurement of valve clearance says that your valve guides are OK if you replace the worn valve. They are not like new but should work just fine.
I assume that you pushed the valve to one side and got your reference, then pushed the valve to the other side with the difference being your clearance. You might also do your check at 90 degrees to your first check and see if you get a difference.
You know, after thinking about how I did this, the valve will not move laterally as I push on the valve head, rather it is going to pivot or cock in the stem guide. So I think you are correct in that my measurement method is poor. Alternatively, I tried this. I do have some micrometers, not good ones, but OK. A valve stem is measuring 0.324". I believe that my mic is measuring about 1/2 to 1 thousand low. So I think the stem is probably closer to 0.325". Next I have a new 21/64" (0.328”) drill bit. The base of the bit is nice and smooth and will just fit into the guide and will not wobble at all, very snug difficult to turn. Although I don't have a bore gauge, the drill bit kind of works like one. So maybe I have 3 to 4 thousands clearance? What do you think? Mike
There are a lot of expensive ways to measure small ID's. The problem of course is expense. There are special bore gages made by companies like Mahr. There are air gages that can get down into that .00005" range and a few others. But expense is an issue. The best "functional" check is probably pin gages that are found in .0001" increments. Most good job shops should have a set. But seriously for what you're concerned about, pin gages in .001" increments should be good enough. You're talking about a Model T that was built over 89 years ago. Clearances were important but tolerances couldn't have been so close as to define them as critical. Therefore Harold's idea of creating your own pin gages is probably more than adequate for what you're trying to do. Measure your valve stems with a mic, and get a good estimate of the valve guide diameters with pin gages. Determine your clearances and go from there.
If it slides freely and there is no "perceptible " side play you are good. If you can feel/see the side play it is a problem.
If your valves have only.001" wear and you can feel the play then "knurling " the guides could work. After all it is only a model T, not a formula 1 engine!!
Les - My sentiments exactly! In fact, if the valve guide clearance isn't exactly per "Ford Factory", I'd sure have them a bit loose than tight 'cause they won't stick, and, knurling helps a bit too by holding bit of oil. Valves/guides can get pretty worn and sloppy and guess what? Those valves will close and seal just fine!
You know, John Browning who, during the Model "T"era, designed the M1911 semi-automatic .45 caliber pistol that helped us win WW2 and Henry Ford had something in common:
That .45 cal. pistol was designed pretty loose, which was a factor that played a large part in it's reliability. You could drop that gun in the mud and pick it up again and immediately fire it! Reliably! And those 4 Model "T" cylinders, sloppy guides and all,......will fire! Reliably!
Remember the first M-16's weren't worth the powder to blow them to h___ until they opened up the tolerances on them and suddenly they stopped jamming when they got a little mud on them. Up until then, good men were dying because they had gotten rid of their M-14's.
Mike, this is what I'm talking about by a small bore gauge:
There are cheap Chinese sets like that, Starrett if you'd prefer, or anything in between. For people that don't use them very often, given that they are a non-graduated tool, an economy set like that will probably do.
That allows you to reach down in the guide and measure at different points to check if it's out of round, flared out at the top and bottom, etc. A quick way to check for extreme issues is to put it in the guide and find the smallest area (usually at the middle) pull it up to the top, and see how loose it is.
It's hard to say what you have based on how you're doing it, but sloppy guides aren't good. What you see in extreme cases of guide / stem wear is it will make your valve seat oval over a period of time.
I'm with Ted on this one. MHO
Walter, I've been away from machining and inspection equipment for too long. I used the gages you're showin a few times several years ago. As I recall they worked similar to the larger telescoping gages and were pretty darn capable of checking smaller ID's. I guess I'll be breaking down and ordering up a set for myself.
Harold, That's a great idea with the GoNoGo gauges. I was thinking about using a drill bit or transfer punch. maybe a letter drill or even a variety of ball bearings? I don't think my snap gages go that small.
Go / No-Go gauges are typically used in production on freshly machined parts, not where you have variables created by wear. Particularly on something with a long bore like this. If you're going to do that, you could just drop in a new valve and figure essentially the same thing. If you goof up and get a Go / No-Go pin stuck in something like this, you'll really be kicking yourself.
Michael, yes, going down in size, small bore gauges pick up where telescoping gauges leave off. Better brands are usually nicer to use, particularly since it is a "feel" type instrument. I think a nice used Starrett set can be had on eBay for about 25% of retail (or double the Chinese set, if you want to look at it that way).
They have other handy uses too if you get creative with them.
Gene - Yeah, I thought I had a good idea too, that is until a couple minutes ago when I read Walters post about the small bore gauges for less than twenty five bucks! And like he says, they'd be useful for other purposes too! Probably typical Chinese quality but for our purposes, good enough!
Thanx Walter,....I had no idea they were available so cheap!
Walter those gauges look good, I'll keep my eyes open for some. Maybe I can afford some better ones that are used. As an aside, I purchased a new valve for the one that was worn more than the others. I was surprised at how long the stem was. I measured it at about 5 1/16" head to tip. My valves are all just under 5" long. So there will be some grinding to do to get it to size.
I have an old 1950's Black and Decker valve machine so that should not be a problem.
I was thinking about how my valve could have worn the way it did. Near the head there was excessive wear on one side of the stem and near the tip the wear was on the other side. I noticed that the spring and keeper were tilted. I was wondering if that could have put some side loading on the valve.
See how the spring on the left is a little cocked. I can straighten that out by repositioning the pin, keeper and spring.
Valve guides are almost always worn hourglass. Keep that in mind if you use the method in your first post to determine clearances. Don't know if repositioning the spring makes any difference, but I doubt it.
Just thinking out loud. Mike