Valve clerance adjustment

[ozon02]

Hi,
I have a question whether valve clearance should be set in the lower limit, in the upper or in the middle. At ambient temperature 20 Celsius?

[goldnsx]

Upper but stiff then. The lower should slide easily.

[duncan]

OK then,
which set of thicknesses and tolerances: millimetres or inches are ‘better’?
Inlet 0.15-0.19mm or 0.006-0.007inches,
Exhaust 0.17-0.21mm or 0.007-0.008inches

[goldnsx]

inches because it's half of mm, more precision. Unless you have a mm-gauge in 0.01 steps.

[britlude]

depends entirely what set of feeler gauges you have in your toolbox! and 6/7/8 thou is easier to get!

[duncan]

Inches may appear more precise but are they are they merely an ‘acceptable’ conversion done by Honda engineers on a true metric tolerance?
i.e inlet is 0.17mm +/- 0.02 and exhaust is 0.19 +/- 0.02, that said, agreed inches are easier to use on a go - no go basis.
My assumption, and it is only that, is that the metric +/- figures are the true tolerance - but that was until you see that the clutch hydraulic bore sizes are in inches and Bose appear to love BA sizing.

[goldnsx]

Honda thinks in mm, not inchs, true. Given that, an US inch gauge let's you adjust them a little bit better than mm in 0.05 steps.

Honestly, take whatever you feel comfortable with and think about what tools they use in Africa for example, that would be a 0.20 mm feeler gauge. :)



0.005
0.1270


0.006
0.1524


0.007
0.1778


0.008
0.2032


0.009
0.2286



The key in this procedure is to adjust it to the desired value, I usually go for the upper, but on the tight side, 0.008 for example, a 0.008 should be very tight but you should not use brute force! Take a 0.007 and it should silde very easily. Try a 0.009 and it should not fit at all even with a little bit more pressure.

Forget about lower values result in more power, that's purely mental masturbation. If you go for the lower limits and the valve tends to diminish over the time it's too tight and you have no reserve left. 1-2 hp more against the risk of taking the heads off the engine is simply NOT worth it.

The other key is to position the blade correctly. The feeler gauge needs to bend a little bit before it is in the position to check the clearance. Hard to describe. If you haven't done it ever before on an NSX DO check it on youtube or any other reliable source.

The other key is to turn the engine and double and trible check your adjustment.

[ozon02]

thank you for the answer Goldi- and I thought I'd put my question wrong;)