adjusting valves

[KenC]

chain guide rails? 8)

Son of a...

[leone30]

I used .008in .010in .012in. gages. Better yet to use metric gages if you can get them,24mm .25mm, 026mm.
The first goes easy between the walve and the roker. the second with some drag, the third does not go. Probably, the best way to set valve clearance is to use a dial indicator. A metal bar with holes against valves installed over the head. a dial indicator head inserted in to each hole sequentially and touch a rocker. Then you set clearance. many years ago i did this way. It was alwaus right. I always did on cold engine.

[u3b3rg33k]

Do it with a herring can lid, use other side after 6th adjustment (compresses too much on 12):

[Philipangoo]

^ The tool is so cheap... and with your valves, I would think you want the gaps to be consistent and accurate. With a feeler gauge you can adjust to the right gauge then see if the next size up won't fit go - nogo style.

[u3b3rg33k]

It works well when you can't find your feeler gauges and you just ate herring.

[r3d e30]

Values for adjusting valves cold is .010 and warm is .012. BMW recomends setting them cold. In my expierence with setting valves on a m20 the actual setting that worked best for me was .011.

[LagunengrunE36]

Why do people push the car or spin the wheels instead of turning the engine by hand?

[u3b3rg33k]

Why do people push the car or spin the wheels instead of turning the engine by hand?

Turning it via the wheels requires no tools.

[Disco Benny]

so to adjust valves HOT just take off VC, unplug AFM, use a 10mm and small allen wrench right?

...Sounds like the tried and true method of valve adjusting

What's the best way to adjust valves while COLD (75' F)

[Beach Bum]

so to adjust valves HOT just take off VC, unplug AFM, use a 10mm and small allen wrench right?

...Sounds like the tried and true method of valve adjusting

What's the best way to adjust valves while COLD (75' F)

Same procedure with less hot oil on your hands and you only have to remove the valve cover. It's also nice to have a piece of wire coathanger or an allen wrench to rotate the valve eccentrics.

[Disco Benny]

I got the feeler gauge, nice. Thanks!

[bmwstudent]

"the valve lash actually gets bigger as the engine warms up" NO IT DOES NOT! The valve lash spec is .012" hot .010" cold. The lash SETTING is larger when hot. Metal expands when it gets hot Nando. The reason you have that lash or space between the rocker and valve tip is to allow for expansion when hot. Did you really mean that or was that a mistake?

[cabriodster87]

Doesn't heat expand valve train components? Therefore lash decreases as engine temp rises. I found this write up, also read the first and second sentence in the last paragraph. I hope this will help everyone.....

What Is "Valve Lash"?
Valve lash is the mechanical clearance between the cam lobe and valve stem or transfer rocker when the valve is fully closed. It's usually checked with a feeler gauge and is some non-zero value on with "mechanical" non-self adjusting valve lifter mechanisms.

Differential expansion characteristics cause the cold clearance to be different than the running clearance and margin is built in to make sure their is always some clearance, especially on exhaust valves. An exhaust valve that doesn't close completely doesn't transfer enough heat back to the head and can "burn".

Cam lobes have entry and exit profiles (called ramps) which are designed to limit the opening and closing acceleration of the valve to limit mechanical stress and also noise. Still, the tighter you set the valve lash (less clearance) the more open valve duration you get which tends to boost top end performance slightly. The looser you set the valve lash the more bottom end is boosted and the more valve train noise you get.

If you have all the valves adjusted too tight idle quality and low end performance may suffer slightly with an attendant small gain in top end horsepower. Looser valve lash does the opposite and results in a noisier valve train.

If you have some tight and some loose that might also effect smoothness since different cyclinders will have different power contributions at different RPMs. Some of the above is a little simplified but you get the drift.
Why Does Valve Lash Need Adjusting?

Too much lash can accelerate wear on the rocker arms, cam followers, cam lobes, valve stem tips and valve seats. How much it does depends on the engine and how far out of spec the lash is. Too much lash also tends to make more noise so you're more likely to know it needs adjusting.

Too little lash is more dangerous both because it leads to more serious problems and because it doesn't make any noise. Luckily the NSX valves do not tend to get tighter so unless they are adjusted incorrectly it should not be a problem.

But just for your info, too tight a lash may allow the lash to close up as heat builds up in the engine - especially if the engine begins to run hotter than normal because it's being worked hard. This gets worse as the engine gets hot because valve clearances tend to close up as the parts heat. That's why the NSX shop manual specifies that you should do the gap adjustment when the engine is cold. Some other engine service manuals will specify seperate hot and cold adjustments. The loss of lash can prevent the valves from fully seating which results in loss of compression and valve overheating. Exhaust valves rely on cooling through the valve seats much more than intake valves, so loss of lash in the valvetrain often results in a burned exhaust valve.

[bmwstudent]

that is correct lash decreases as engine temps rise due to EXPANSION of the parts i.e. the valve actually gets longer and the rocker does too

[cabriodster87]

Well, I have known this for years, but it was late last night and was confused because i didn't comprehend the meaning of your statement above. when i read:
"the valve lash actually gets bigger as the engine warms up" and "The lash SETTING is larger when hot." simple mistake on my part, then after i posted and read it again i caught the meaning. My bad, didn't mean to step on your toes.