I had a burned intake valve replaced at 12000 miles. the mechanic said the top of the guide wont hold a seal on, so he put it together without the seal. I think the stem was mushroomed and forced through. he said they remove the seals on racing engines for lubrication? anyone ever have this happen. im thinking of having it done correctly and at the mileage maybe replacing the piston, I think it was run hard because how slow they are on the road. any advise is appreciated thank you.