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Valve adjustment

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66healey

66healey

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I'm getting ready to adjust my valves and have run into a problem. The factory manual and Haynes manual both say to adjust when the engine is cold. However the tag on the valve cover says to adjust when hot. Which one is correct?
 
What car do you have? You may have a manual for one year and valve cover for another.
Oh, I see your avatar is 66 Healey. That's what I have, and I understand that the valves are to be set cold.
 
66healey,
According to the BMC Workshop Manual (1968) the Valve rocker clearance should be set at .012 in. (.30 mm) cold. If you have a competition Mk II or III set the valves at .015 in (.34mm) cold. See General Data p. 10.

Stephen
 
Back about 4 to 5 years ago I brought up this same topic. The consensis of opinion (Dave Russell and others) was that they were not different enough to matter. How fast are you at adjusting the valves? They will not be the same when you start as when you finnish if you are like me, so cold works for me.
Are you aware of the rule of thirteen? Adjust valve #1 with #12 open adding to the number 13 and so on. Plugs out and car in 3rd or 4th and role using front wheel you are standing by. I use a Snap-on valve adjuster which makes it fast and easy.
 
I ended setting them after the engine had cooled for about an hour. I dont think they had ever been adjusted, as my father had this car since 1967 and I dont ever remember him adjusting them. Only had to adjust 3 valves though, and they were all only slightly tight.
 
I'm sure you did it right. Hot or cold, the measurements are the same.
 
I got my Healey after several years of MGBs, and always adjusted their valves at .015" cold, as per the manuals (all in agreement). Seeing that the Healey was calling for .012" hot, I compared the settings under both conditions.

The conclusion was that .012" hot was the same as .015" cold.

Just remember: loose valves won't cost you money; tight ones will!

The only "cooling" an exhaust valve gets, is the time it can dissipate heat while touching the seat. A tighter setting minimizes the time spent on the seat. The intake valve gets a nice cool charge across it every time it opens, while the exhaust valve gets doused with 1375 degree spent gasses (assuming a correct mixture; even hotter if you're on the lean side) each time it opens.

Give the poor exhaust valve a break, and set them all at .015" cold.

Edit: aftermarket cams (like my 3/4 Isky) generally require even looser clearances; mine are .018" intake/.020" exhaust.
 
Thanks for the replies. Ive got a new valve cover gasket on the way, when it shows up I'll loosen the settings on the exhaust valves to .015.
 
Randy -

If you check, there will be no difference between 0.12 hot or 0.12 cold on a Healey motor. I've checked several times. 0.15 will only reduce valve lift slightly. Main thing is that they are all set the same so the car runs smooth.
 
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