Valve lash question

[XperiMental]

I bought my first NSX about a month ago and it was in need of a timing belt and valve adjustment. After reading all I could on the matter, I decided to do it myself. It went perfectly, but as I was doing the valve adjustment I noticed that all of the valves were about .002” tighter than the minimum spec. From the records I have on the car, the last adjustment was about 30K miles ago. I talked to one of the service personnel at the dealer that did the adjustment and he said that it is typical that the valve lash gets tighter as time goes on. This just doesn’t seem to make much sense to me (as things wear it would appear that the gap would get larger). Do most people agree with this and does anyone have an explanation?

 

[dnicho05]

With normal valve and head wear, the valve lash (clearance between the base circle of the camshaft lobe and the camshaft follower or tappet) does get smaller. This is due to the wear that occurs from the normal contact made between the valve and the valve seat. As time goes on, metal does wear away from both surfaces and the valve recedes up into the head/valve seat, thus reducing the valve lash gap.

Hope that helps

 

[XperiMental]

Ah. I forgot about the wear occuring between the valve and the seat. That makes sense. The only wear I was considering was to parts on the cam side of the head. Wear to parts on the cam side of the head would increase the clearance and wear to the valve and the seat would decrease the clearance, but it makes sense that the fastest wear would be to the valve and seat. Thanks for the response.