Bad new valve guide

I have been posting about this problem on the Farmall site and have received some very good advice but I'm getting desperate so I'm posting it here too.

I have an F20 with a rebuilt head, new guides, springs, valves, seats, the works. When I first started the tractor up after putting it together it ran 10-15 minutes, then #1 exhaust valve would stick. After a cool down I could gently pry the valve back up and after a restart it would stick again in 10 minutes or so. I pulled the head and took it back to the machine shop. The valve was moderately tight in the guide and was galled on the bottom part of the stem where it exits and reenters the guide. On friday I picked it up from the machine shop but was in a hurry and didn't ask him what he did to solve the problem. Yesterday I put it back on the tractor and after starting the tractor it stuck within five minutes. Someone on the Farmall site sounded like he had this problem before with a bad new guide in the past. What do you think? I have been squirting oil on the valve stems while it ran hoping to get some lube down there but it didn't work. The guy who does the heads at this machine shop is competent, I am not questioning his abilities, he has done a ton of heads on all kinds of engines from the smallest to the biggest. The head is coming back off today and is headed back to the machine shop tomorrow but I would like to have some ideas to throw at him when I get there. Thanks

Your valve guide was not honed (sometimes in a cheaper shop, reamed or broached) to the correct valve
clearance. If the OD of the valve guide was greater by to much on the bore in the block it's to be
pressed into, it can become distorted. The engine warms up, the valve guide expands, narrowing the
clearance and the valve will stick. You want around .003" on a valve to guide clearance. Someone is
simply not doing their homework. If the shop is using a reamer on a cast iron valve guide, it will
wear very quickly and not clearance properly. Honing is by far the best procedure.

I would replace the valve and guide. One of
them wasn't heat treated properly or made
from the wrong type metal. Too much work to
guess which one.

In 1979 I bought an old man's property
and most of his lifetime collection of
old tools. One of his tool collection is
a set of adjustable reams he used to work
on engines. I would suggest you clean up
the valve guide with a ream and if
necessary make it a tick larger. Then you
will need to check to see if the valve
seat needs touched up.

Probably an exhaust valve sticking . The clearance must be met or they will seize in the guide. A guide is not even a moving part. What is the spec for ex. Guide clearance?

i would replace the guide and valve, probably save having to pull the head again.

This is a large reputable shop, one that everyone in a large surrounding area around here recommends. I have full confidence the machinest reamed the guide to the proper specs. I am leaning toward doing as a couple of you recommended and replace the valve and guide.

The valve may have a heat sensitive stress in it causing it to bend when heated. A different valve is in order. Reaming the guide to .0015 will also help. Valve guide
prelubricant will provide a buffer for initial run in. Briggs and Stratton Valve guide lubricant is one!! Jim

Jim you might be on to something. The valve stem galls right where it goes back up into the guide when the valve closes. The stem is OK above that area.

You may be on to something. Back in the 60's I had a VW bug with 50K miles on it that would stutter and stop. After 20 minutes it could be restarted. There was bakelite guide for the pushrod that operated the fuel pump. When it got hot it would bind. The pushrod was 8mm in diameter. I worked in a machine shop at the time and made a pushrod from a piece of 5/16 drill rod. Ran it to well over 100k without anymore problem. (8mm = .314 vs. 5/16= .3125)

first of all ask him what clearance he has given the guides. if less than .003 they will stick. have you added some 2 cycle oil to the gas , as that has more benefit than top oiling. plus ask what he has done to rectify the sticking. you saying all new parts so clearance has to be the issue. also when valves are assembled in the guide they are to dipped in auto trans oil for prelube. i have experienced valves sticking that have been stuck previously. due to the rust and gunk in guide and stem. proper job is to remove from guide and clean guides with a guide brush.

That is also the hottest part of the stem, and the most likely to stick if the guide is undersized.