Daihatsu Skywing (G23 3-cyl engine, like Charade) - Valve Clearances: Hot v. Cold? - edlithgow

The Charade manual says valve clearances (0.2 mm) should be adjusted on a hot engine.

I find this a pain, since its a small engine and it cools down pretty quickly, especially in the howling chilly grit-laden gale that always seems to blow up when I have an engine open. IIRC all the other engines I've had except the last one (Sierra with hydraulic tappets) specified the clearances cold, which is a much more definate, non-moving target.

The cold valve clearances (0.15mm) are buried in the engine rebuild section of the manual, but it says these are initial settings only and should be re-adjusted to the hot settings once the engine is..well...hot.

Why is this? I can't see any theoretical reason why the relationship between the cold clearances and the hot ones would vary, so if they are both set accurately, they should be equivalent.

My best guess is that "cold" will vary with climate, so it'll be different in Texas in the summer and Tomsk in the winter, whereas "hot" is controlled by the engine thermostat and (if one does the job quick enough) fairly constant.

If that's the reasoning, it doesn't seem to have bothered many other car makers (eg Honda).

I've tried this twice using the "hot" settings. First time I couldn't see the timing mark so just went by cam-lobe position, though visibility of the cam lobes isn't very good on this engine. Also it took me a while and the hot setting perhaps wasn't appropriate by the end.

Since it didn't sound any better I tried it again using the method in the manual (set 4 of the valves on the timing mark, then the other two after 180 degree crankshaft rotation) being careful to warm the engine up thoroughly. This went quicker but the engine sounds worse.

Tempted to ignore the manual and use the "cold" setting next time, so at least I won't be rushed. Is there any reason (that I havn't thought of) not to do this?

Daihatsu Skywing (G23 3-cyl engine, like Charade) - Valve Clearances: Hot v. Cold? - focussed

"Since it didn't sound any better I tried it again using the method in the manual (set 4 of the valves on the timing mark, then the other two after 180 degree crankshaft rotation) "

That doesn't sound right for a three cylinder engine-three cylinders are going to fire in two crank revolutions. So thats 360 x 2 = 720 divided by 3 = 240 degree firing interval.

A four cylinder engine has a 180 degree firing interval 360 x 2 = 720 divided by 4 = 180

So to find tdc for cylinder 1 turn the engine over in the correct direction of rotation until the valves on cylinder 1 are "rocking" ie exhaust closing and inlet opening-make a chalk mark on the pulley and adjacent part of the engine. Then turn the engine one full turn on the chalk mark again. That gives you tdc cylinder 1. Set the valves on cylinder 1. Then turn the engine 240 degrees, that's 4 flats on the hexagon crankshaft bolt. Set the next cylinder in the firing order, most three cylinder engines have a firing order of 123 but check this. And then turn the engine another 240 degrees and set the last cylinder, this should bring you back to the chalk marks again.

Three cylinder engines are always a pain in the a*se to set the valves on because of this odd firing interval-done a lot of them.

Daihatsu Skywing (G23 3-cyl engine, like Charade) - Valve Clearances: Hot v. Cold? - edlithgow

Thanks.

I did it again pretty much by the book, except I used the "cold" (engine rebuild) 0.15 mm feeler guage with a sharp kink in it to improve access. Sounds OK now

I'd guess the problem last time was a combination of it cooling while I was doing the job, and excess drag from the flexed feeler guage.

Book says I should do it again "hot" so I suppose I will, but I'll wait 'till it isn't so b***** windy.

 

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