T_ypEr

I have a 2000 Civic EX coupe with the D16Y8 VTEC engine in it and it sounds like it needs a valve adjustment. I already found the valve lash to be:

intake = .007-.009"
exhaust = .009-.011"

My questions is why they give a range of measurements where the valves should be instead of one number that would be the optimal valve clearance with the piston and open at the perfect time and height. I guess I just don't understand what the difference would be if I adjusted, for example, the exhaust valves to .011" instead of .009". Is there any performance or efficiency difference?

tayyab74

There is wear n tear to the engine with the passage of time. This difference is due to that.

T_ypEr

So as time passes and the engine is used, the optimum valve lash will change?

Former User

Anywhere within the spec clearance range is fine. I generally adjust them smack dab in the middle of the range, but preferences vary.

T_ypEr

Cool deal! Just out of curiosity, if I were to adjust the valves so they open to their maximum clearance number (intake .009" and exhaust .011") would that affect performance and gas mileage at all?

motegicivic

I doubt that little of a tolerance would have any effect.

T_ypEr

Ok thanks man!

98civdx

When we adjusted my friend's, we went to bottom end of spec in a attempt to shut the thing up, and he noticed no ill affects.

T_ypEr

So after adjusting the valves (finally), they seem LOUDER. My dad and I checked them with the feeler gauge and adjusted all the intake to the same spec and exhaust to the same spec. Just out of curiosity, would it make them louder if, for example, adjusted the exhaust to the higher end of the range (.011") and the intake to the lower end of the range (.007")? Also, when I rev the engine up to about 3.5K rpm, the engine comes back down to about 2.5K rpm and then drops faster back down to idle. Before my girlfriend's 1992 Civic sedan was fully tuned up, I noticed this happening. When we finished with it, the revs dropped evenly.

azkicker0027

i forgot, but at what temperature can the valves be adjusted? i remember doing mine while changing my oil when i got in the shop after about a 20 minute drive from dead cold. i did have to adjust my idle after the valve adjustment to resolve some minor fluctuations.

98civdx

Do it when the engine is cold.


No one wants to be in there messing with a engine that hot as hell!

T_ypEr

It has to be under 100ºF

gotz2b16

I also usually set the valve lash in the middle of spec..

YOU MUST ADJUST THEM COLD.. Meaning the engine has to be below 100*, More typically around room temp like <80*.. As a tip of advice, use 2 feeler gages to set your lash.. for instance, If you're adjusting to .010, then pull out a .010 and a .011 feeler.. use the .010 to adjust, then if adjusted right, the .010 should be able to go back in after you remove it, and the .011 should not fit if adjusted right..

Also.. Setting your valve lash too tight to try and quiet it up (If tighter than spec) can lower dynamic cylinder pressure, raise operating temp within the cylinder, and can most definitely burn valves!! Don't adjust valves tighter than minimum spec!!!