Gold Lifetime Member
Join Date: Jan 2005
Location: 2 Dog Town in West Texas
Re: bent pushrods
Knurled valve guides is a cheapo way to correct excessive stem / guide wear. It involves of basically making threads into the inside of the guides. It works for a while and provides extra lubrication as the little threaded groves hold oil. This sometimes also causes problems as when the valve stem is fitted back into the hole,,, the stem head can break one of the little threads and fold it over. With a heated engine, this little particle can swell and cause the valve stem to tighten and gall thus stick the valve, either in full open or closed position. So if the force is great enuff, you will or could either bend the next weakest point with would be the push rod or it could cause the valve to hang open,, at the wrong time , thus the piston comes up and sorta closes it for you,, Not a good thing,, it will bend the valve over time or go thru the piston top.
So tapping the piston could cause the little ting sound . Oversizing the valve head would not or should not have anything to do with this . I had one such case on the knurled valve guides and it did not show up until on a long trip. Need to go back to the shop and ask questions, my guess is that if its more than 90 days old, its yours.
I am only suggesting this ,, your case may be differant. Since you have heads off, I would take each valve apart and look for trouble. Hope you dont have any broken springs that are stacking. Also becareful that the valve stem does not have a worn mushroom tip as this also will cause scratches and gouges into the valve guide area when you pull valve out. Check your seals too. Good luck
TC # 349
Zdld17:69 Z/RS,306, NOR141111, 9N554XXX, 12A, X3G, 59/59,723, AFR 195,CCC282/290HR, TKO 600, BU1122B1E Owner since Dec 1968
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Last edited by zdld17; Jan 9th, 06 at 06:50 AM.