Question about valve clearance.

[YamahaV8]

I was wondering about valve clearaces and solid lifters. I am a aircraft mechanic and have done piston engine overhauls for aircraft engines for over 2 years. I know with aircraft engines that the valve clearances actually get tighter over the life of the engine due to the fact that the valves will over time pound into the valve seats (which is not a bad thing) slowly closing the valve clearance. So I was wondering if it is the same for car engines or if car engines mostly get looser clearances over time?

[UndrgroundRider]

Depends on the engine and the metals the parts are made out of. You basically have two groups of parts, the valve seats, valve heads and then "everything else." One group wears faster than the other. If the valve seats/heads wear faster the valve moves closer to the rocker arm and the clearance decreases.

If the rockers,cam lobes, and everything else wears faster then the clearance increases and it gets loser. Most engines are this way and get looser over time.

Most motorcycles and such get tighter over time.

[YamahaV8]

^^
OK makes sense. I will have to find out about my engine in particular. My heads and valve train are Yamaha (Taurus SHO) so I wonder if it follows a motorcycle wear pattern like you said and they get closer.

[UndrgroundRider]

I would assume they would get looser. Although even on a car you should really check the valve clearance every now and then. If you have solid lifters you can do this very easily with a feeler gauge.

[YamahaV8]

Originally posted by UndrgroundRider
I would assume they would get looser. Although even on a car you should really check the valve clearance every now and then. If you have solid lifters you can do this very easily with a feeler gauge.

Yeah the checking part is easy it's the 3 hours to dissasemble the intake runners, surge tank, ignition coils and finally the valve covers that sucks.