valve prob.

[Anonymous]

My dad has a 66 mustang 200 I6 3spd, about a month ago he was moving it in the yard and it started missing bad, after investagating we found that the #3 cyl. ex. valve was stuck so we pulled the head replaced the valve, pushrod, rocker arm, lifter, we did seat the valve with valve grinding compound.
Now it's been about a month and we're finding a new prob. When he cranks it every now and then for the first 5 to 10 minutes the #3 cyl. misses, then it just clears up and starts running smooth.
When its missing the plug is firing.
So all you experts what could be causing this :
Thanks

 

[rbohm]

8) are you sure the plug is firing? or do you just have power to the plug? plugs 3 and 4 tend to foul easier than the other because those cylinder run richer than the others. check the compression, and compare it to the rest of the cylinders as well.

 

[MustangSix]

Definitely check the ignition first to ensure you have a good spark to all cylinders.

Maybe you still have a valve sticking. If the valve guide was galled, it might be siezing the valve until it warms up a bit.

When the engine is cold, try a compression check. If #3 is substantially lower, it's probably doing it again. Then fire it up and run it until the symptoms stop and repeat the compression check. If #3 is normal, then you know for sure.

To fix it you'll need to remove the head and valve and ream the guide to clean it up. You might want to knurl it, then ream it to ensure it gets enough lubrication.

 

[Anonymous]

The engine ran fine today, we pulled the plug anyway and it looked ok, the fire on it looked good too.
When we replaced the valve he said he reamed the guide

 

[BIGREDRASA]

Have you checked the lifters? Could you have a problem with that one lifter pumping up or leaking down.