Exhaust valves.... barely in spec good enough? (1 Viewer)

[AaKnight]

So at 165k I'm doing hg and valves. A few of the exhaust valves had some pitting that I had to polish out.... I now have four valve clearnces that measure exactly 0.01" (0.252mm) .... literally on the low line for being within tolerance.( Which is 0.25-0.35 mm (0.0098-0.0138 in))

Will I notice a difference or see any benefit to bringing them closer to the center of the spec? Or would it be only for my piece of mind?

Is the perfectionist part of me going too far, should I just call in-spec "good enough"? so im really curious.... What would you do?

for the pic, the shim size is the first row, and the current measurement is on the right.

 

[leonard_nemoy]

If your already in there it seems like it would make sense to just get them right in the middle of the range and than drive it for another 165K

 

[audi2nr]

Let me get this straight.. you pulled the exhaust valves for pitting on the seat area? A few things I can think of... first off valves cool themselves off via contact with the valve seat which draws the heat out of them, the longer the contact the cooler the valve (larger the cam to lifter gap), less contact = less cooling (smaller cam to lifter gap) and the higher risk of a burned valve.. now you effectively tightened your cam to lifter clearance because you took material off of the part of the valve that contacts the seat. Imo the exhaust side should be on the looser side (more gap) vs tight side (less gap) especially when you account for the parts heating up and expanding.. if your lifter gap is too tight you can effectively hang a valve open causing a lower compression condition.. probably not at the clearance you have currently but it can happen. I'd run loose on the exhaust and tight on the intake.. tight on the intake will allow you to use as much of the intake cam lobe as possible giving you the most lift which is good for power.

 

[fjc-man]

And furthermore, as the contact surface on the seats and valves wear the clearance gets smaller (tighter) not greater.