Valve Stem/Guide Wear

[WMarshy]

Im looking for info from the guys who have had their heads apart and worked on their valves. Just curious... have any of you seen xs'ive wear to the valve stem or valve guides? Have you even measured the valve stems for wear when you had them out and if so, do you know what the factory gives for specs on wear (or is there an engine builders general rule of thumb)?

I see a guy on ebay offers a valve guide service where he bores out the guide and installs phosphor bronze liners for $125. "The process involves boring the stock guide and pressing in the phosphor bronze sleeve. It is then swaged in place and precision diamond honed to the correct clearance. As with all valve guide replacements the valve seats will need to be re-cut which is not included in the price of this listing." Any thoughts about installing liners vs new guides?

That seems all fine and dandy but if the valve stem is out of spec then it wont matter how nice the guide is... The reason for these questions is, when I go to install my BB kit I want to make sure the head is in top shape and up to the task. I see a NOS intake and exhaust guide on ebay f/s and thought about scooping them up. That way if I ever needed to replace my guides I could have someone machine me some if need be...

[bikerphil]

If the head you are working on has low miles, I wouldn't worry about it, JMHO. I'm running a head on a 79F now that has over 120K on it, seems to be just fine, no oil consumption, have only replaced the valve seals. YMMV

[sparks]

Not any experience with motorcycles but on cars/trucks/tractors, we had great success with knurling the guides when the valves got a little sloppy. There were also some very good aftermarket guide seals that did a fine job. Certainly a lot better than the "o" ring type of guide seals that come with the gaskit kits.. I dont think I would bother replacting the guides unless, before the tear down, you had a lot of oil consumption through the intake valve guides or, you notice the valves wobble a lot when you put them in the guides after the head is cleaned.

Lee

[TADracer]

According to the Clymers manual the stem clearance (cold) should be .0004" to .0016" for the intake and .0010" to .022" for the exhaust.

On the high side of the tolerance I imagine that would be a very very very percptable wiggle in the valve if you try to move it side to side.

Stem diameter the last time I measured mine was between .2745" and .275" for both intake and exhaust.

So that is telling me the guide diameter should be around .2755" for the intake and .276" for the exhaust.

Hope this helps ya.

[BA80]

Valve guide wear isn't an issue with the overhead cams. There isn't any side pressure on the valve stems with the bucket and shim setup. It's all transferred to the bucket.

They just go happily up and down.

Unless you have a bent valve.