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Discussion Starter #1 (Edited)
While doing an intake system leak down test,I found 3 cylinders,on the same side head,with leaking Intake valves. The engine was running fine,but I was looking for the source of blue smoke at idle. I found two rocker shaft mounting block screws,that go into the intake port,leaking air,which would be sucking oil as the engine ran. The 3 leaking intake valves caught me by surprise!
Oh well,off with the head and a valve job!
Last time I made a pass at the track,it ran 12.15 at over 117...skinny street radials all around...245-40-17's,with 3 leaking intake valves?!!
 

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Mus408 said:
While doing an intake system leak down test,I found 3 cylinders,on the same side head,with leaking Intake valves. The engine was running fine,but I was looking for the source of blue smoke at idle. I found two rocker shaft mounting block screws,that go into the intake port,leaking air,which would be sucking oil as the engine ran. The 3 leaking intake valves caught me by surprise!
Oh well,off with the head and a valve job!
Last time I made a pass at the track,it ran 12.15 at over 117...skinny street radials all around...245-40-17's,with 3 leaking intake valves?!!
I don't envy you. If I had to pull the heads back off the Cougar, I'd probably cry and whine like a baby. And then not do it anyway! :lol:
 

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Discussion Starter #5
Intresting find!

Head is off and I did a pressure check,on the bench, of each intake port. All four leak in the same general area around the Intake valve ...the area between the Intake and Exhaust valves,plus 2 leak in a couple other areas.Seems to be at the valve and seat interface. Just for the fun of it,I will check the Exhaust valves.
If it is leaking at 20 PSI,imagine during the compression stroke! Could be losing a few HP!
 

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Discussion Starter #6
Yep,all the valves are leaking to some extent. My theory...after several thousand street miles,even with the hard seats and high quality stainless valves,your valve job turns to junk. Now,it may not show up much in performance right away,but be a steady decline. I'm sure unleaded fuel still causes more wear,even with the hard seats. I remember seeing pitting in the seat area and on the valve angles when I refreshed the engine last year. It looked minor,and the heads only had around 3,000 miles at most on them!
 
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