All right on the money after many passes EXCEPT #1 exhaust which had no lash. I noticed last time I raced it sometimes starting it, it would sneeze out the carb. I'm thinking because valve hanging open. What would cause one valve to lose lash? I know if you gain lash it could be wiped cam lobe. Valve seat recession? Failing keepers?
What kind of cylinder heads? How much did you lose? A sunken seat is the mostly likely scenario if they are iron heads. If you have alluminum heads then I would be very nervous that the valve is failing which would lead to catastrophic failure. Keep in mind the valve cools when its closed. If it was hanging open some its possible that valve head has been red hot, which is also not good..
Pull the rockers and lay a flat edge across the valve tips. You'll at least get an idea of how much that valve has changed. If its a substantial amount I would pull the head before making anymore passes
Good advice...but going to Yellowbullet and if it survives I'll recheck lash and do what you suggested.
With a Aluminum head you have a seat that has got pounded deeper into the head and this also means that since you gave up your lash to this condition you have also lost about 20 psi of what might be very much needed seat spring pressure. This can be a very bad circle of events! The seat being that it's moving may also rock around, once that starts you can drop a seat and or snap a valve head off. If you have lost enough spring seat pressure and are floating the valves long enough then the above that I posted will take, it's just a matter of time. The least I would do at this point is yank that head and have a oversized seat installed even if you have to get a custom one made up. Install it tight and do whatever valve bowl blending or porting that's needed to get it to flow like the others. Minimum seat wall thickness to me is 210" for a common height seat, any more meat removal then that due to valve bowl blended work and or porting and you will run the risk of having them loosen up, and that's real bad! You so far have dodged a bullet by catching that reduction in lash, don't push it and not yank the head and just relash and run the thing!
OK, got me worried now. I'm going to pull the rockers and see if #1 exhaust valve tip is higher than the others and go from there.
Installed height is same as the others so I am going to chalk it up to adjustment error last time I set the valves. Maybe when I tightened the nut the adjuster moved. Hopefully it didn't hurt the cam lobe with no clearance. Or warp/cook that exhaust valve..... Fortunately with aluminum heads valve clearance increases when hot so maybe that saved me.
9 seasons on this motor so I start to worry but both my machine shops that I used retired so trying to keep running this thing.
