The Ford Barn

quickchange · 01-03-2024, 08:08 PM

Local here has gone through 2 sets of mushroom stem stainless valves, has had engine rebuilt, stock with adjustable tappets, new valves, new springs ,std cam grind. stock head, engine builder gave 12 thou clearance, problem has occurred rear valves leaking, now seat where recut etc, 6000 miles on pulling down they found all valve stems bent ??? some as much as 20 thou run out, Im thinking not enough clearance as some came in at only 8 thou, they also had fitted new split guides , Now this has happened twice ?? Of course owner blaming stainless valves ??Do in fact stainless valves expand greater than original ones ??? & should have say 13-15 thou clearance ,
Anyone had this problem before ?? The vehicle has correct timing & not running lean ,The owner is a retired mechanic so no dummy , Please feel free to give us your thoughts, Thanks in advance , Derek from a hot dry NZ,

01-03-2024, 08:08 PM	#1
quickchange Senior Member Join Date: May 2010 Location: Nelson. New Zealand Posts: 2,026	Stainless valves problem Local here has gone through 2 sets of mushroom stem stainless valves, has had engine rebuilt, stock with adjustable tappets, new valves, new springs ,std cam grind. stock head, engine builder gave 12 thou clearance, problem has occurred rear valves leaking, now seat where recut etc, 6000 miles on pulling down they found all valve stems bent ??? some as much as 20 thou run out, Im thinking not enough clearance as some came in at only 8 thou, they also had fitted new split guides , Now this has happened twice ?? Of course owner blaming stainless valves ??Do in fact stainless valves expand greater than original ones ??? & should have say 13-15 thou clearance , Anyone had this problem before ?? The vehicle has correct timing & not running lean ,The owner is a retired mechanic so no dummy , Please feel free to give us your thoughts, Thanks in advance , Derek from a hot dry NZ,