I want to check the valve guide bores in an automotive cylinder head. I've seen some small-bore micrometers that cost several hundred dollars. These are out of my budget. Can I get an accurate measurement with the less expensive "split ball' type gages, some of which are sold under good names like Starrett and Mitutoyo, and a regular flat anvil outside micromeeter? Thanks
Valve guide clearance can be checked with a dial indicator.
Put the valve in the guide, wiggle it. This is the valve clearance. You could knurle the guide to take up clearance if excessive.
Those spilt types are okay, we are not talking micro fits, more like 4thou to 6thou is okay. And some valve guides take a seal on the top....automovtive machine shops deal with all of this...
xman
Small hole gages are accurate to within a couple ten thousandths in the hands of someone capable (machinists use them routinely in that capacity). The big problem you're likely to encounter is elongated or tapered guides, which can be a challenge to measure.
Harold
I use pin gauges for small holes, these can be had in set with .001" steps. I got mine offf the scratch and dent table at MSC, they regularly run sales on them. This will not tell you how oval the hole is, only that the hole will pass a certain pin size.
Usually the engine overhaul manual will have specs as to how much side play is allowable on a valve stem, mesured either with a dial indicator or a factory jig. In used heads, the guides are usually worn tapered, oval or both. Guide replacement is usually fairly easy, I'd still get a machine shop to do it if this is your first head and you are actually planning on using the head in something you want tor run for a long time. Experience counts, here.
Stan
Or you could make a cerrosafe cast and easily measure everything with outside mikes.
I doubt you would get the cerrosafe out---the guides wear in an hour-glass shape--in the plane of the rocker arm--
>
New valve. Used valves may have wear of their own.
Yes. Those will work just fine. With a good feel you can measure with those down below a thou.
Jim
Stan and Harold beat me to it; but small pin gauges are cheap, and the guides will be tapered, big bell at the bottom on any motor.
If it has seperate guides already, send the wife out shoppping for the day, get some dry ice for the new guides, crank up the oven and have at it.
Cerrosafe is designed to shrink to assist removal, then expand later so it is accurate 1 hour after casting.
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