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Correct Valve Lash setting

Scotty

Scotty

Silver Level Sponsor
I've been setting my valves at 12 and 14 and just read some folks set them at 10 and 12. What's the difference and what is the correct one for a 1725? My valve train is original to the engine if that helps. Thanks in advance!
 
10/12 is tighter tolerance and will be less clatter.. but also more potential for things going wrong if you don't get it right and remember the rocker tips an groove and cause misread on tolerance
 
If valves were set correctly at .012 and.014 HOT, why wouldn’t the COLD setting on the same car, after it cooled, be correct? I know the different metals have different rates of expansion and contracting. But wouldn’t that cold setting work correctly when that engine is again heated up? It must be ok, because the engine cools after the HOT settings are done. Then when you start the car the next day the settings are COLD and then heated back up to the HOT setting the next time it’s driven.
 
I hope this is not hijacking the thread ( not my intention as it goes to the central question) but I am intrigued by what nsbluenose adds to the query. Having set my valve lash “hot”, does it really matter if one waits until they get cold again — check the lash at cold and then the next time set the lash at the most recent cold reading?
I set mine hot because that is the prevailing thinking, but it was truly a pain the butt— warm day, sweating, hot to the touch. It would be nice to be able to take my time wearing a sweater, on a 65 degree day and set a proper lash.

Be well all
 
I set them cold with the specified hot dimensions and never had an issue that. No noise whatsoever, but still fully closing valves in hot condition. Don't understand why Rootes specified "hot" at all. Not to mention the burned fingers of anyone really trying to do that :rolleyes:
 
bernd_st said:
I set them cold with the specified hot dimensions and never had an issue that. No noise whatsoever, but still fully closing valves in hot condition. Don't understand why Rootes specified "hot" at all. Not to mention the burned fingers of anyone really trying to do that :rolleyes:
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It's the UK... Cold the car and your fingers are frozen....
 
Why set them Cold:

1) you can take your time, it will not get colder.

2) everything is at the same Temp, How Hot is HOT and how to get there AND stay?

3) No getting Burned.

4) it is easier.

DW
 
I guess we can all only speculate as to why the factory says to set them while really hot. From my experience, 90 degree (F) day, drove the car for about an hour and then pulled the car in the garage and adjusted the valves to the factory specs. The next morning, I checked gaps "cold" and found them to be .002 - .003" smaller. So, if you use the factory spec when cold, you may be running a bit big when hot. No problem other than it may be a little noisier than it should.
 
Mike, so if you set then at .010 and .012 when COLD you should be pretty much bang on at .012 and .014 when HOT. Am I correct in my reasoning?
 
Mike O'D said:
I guess we can all only speculate as to why the factory says to set them while really hot. From my experience, 90 degree (F) day, drove the car for about an hour and then pulled the car in the garage and adjusted the valves to the factory specs. The next morning, I checked gaps "cold" and found them to be .002 - .003" smaller. So, if you use the factory spec when cold, you may be running a bit big when hot. No problem other than it may be a little noisier than it should.
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Ok, so .10 and .12 +/- cold. Makes sense. Remember the old high school experiment with the ball and ring. The ball wouldn't go through the ring until you heated the ring (thermal expansion and all that). I've been setting them on and off for the better part of 50 years; hot, cold and in the 60's with the engine running and never found one bit of difference in the noise or performance unless something happened to make one of the setting way out of spec.
 
The recommendation to use .10 and .12 is based on the assumption that your rocker tips are well worn, thus giving overstated lash readings. But if a PO, for whatever reason replaced the original rockers with new or refurbished ones, you might have a problem down the road with a mysterious backfire that won't go away.
 
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RootesRooter said:
The recommendation to use .10 and .12 is based on the assumption that your rocker tips are well worn, thus giving overstated lash readings. But if a PO, for whatever reason replaced the original rockers with new, you might have a problem down the road with a mysterious backfire that won't go away.
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Are you talking about hot settings or cold setting? I’m working on the assumption that .010 and .012 cold setting is a close equivalent to.012 and .014 at hot. Worn tips or new tips.
 
When it comes to settings, its the final, hot settings we're aiming for. Cold settings are just for "roughing it in" so the engine will run OK until it gets hot and you can do the re-set. Better to err on the side of looseness when setting them cold.

Because I don't know where my rockers were more than 20,000 miles ago, I stick with the factory 12 and 14 to cut down the chances of burning a valve. 10 and 12 (hot) is not a bad gamble but because I sometimes drive my Alpine hard and hot, I choose to avoid it. Someday I'll get those rocker tips smoothed out and know for sure what I'm dealing with. I guess I've been lucky, but I've rarely had to re-adjust the valves more than .001.
 
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RootesRooter said:
I don't know where my rockers were more than 20,000 miles ago, I stick with the factory 12 and 14 to cut down the chances of burning a valve. 10 and 12 (hot) is not a bad gamble but because I sometimes drive my Alpine hard and hot, I choose to avoid it. Someday I'll get those rocker tips smoothed out and know for sure what I'm dealing with. I guess I've been lucky, but I've rarely had to re-adjust the valves more than .001.
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Aren't there "wire" feeler gauges? ... I can't seem to find any except to gap plugs. I've got a set of very tapered ones that work decent Had an 'ol mechanic friend, now gone .. that made his own out of piano wire I believe .. mic.ed them out .. was great for worn rocker tips/valve ends

....... David.
 
There's another way to measure the gap, for situations where the rockers are pocketed and not destined to be resurfaced soon. You can use a dial indicator set up on the top of the rocker, directly above the center of the valve stem. Zero out the dial, then measure the movement. It's not perfect, but it's about as close as you'll need. I have done this many times, using a Vice Grip and a flexible gooseneck. Mine is a Starrett (far too pricey), but this setup, below, would do the job just fine. It's also great for checking road wheel runout, crank shaft end-float, valve lift, brake rotor warp, and many other diagnostic jobs. Definitely pays for itself in a few years of work.

https://www.amazon.com/Neoteck-Automotive-Maintenance-Industrial-Processes/dp/B0CYPQHDV7

1736484913630.jpeg
 
There is also the question of the margin of error with them. I just did adjustments on my car. I haven't done it in ages. I now have the roller rockers. I found that it was difficult on some to get exactly the same feel. They seemed either just tighter or just looser than my fingers "feel" the tension. I have always wondered just what the right "feel" is and believe everyone has a slightly different sense of that. So I assume there is a decent margin of error in the numbers.

I erred on being looser, based on the idea that a "tappy valve is a happy valve." Not sure there is any validity to that phrase.

I also, sadly, set them as 012 and 014, and someone after suggested that 013 for both is how the Holbay cam is supposed to be. I can't find what I thought or new it was supposed to be when I first got the cam/head.

I'm going to redo it anyway because one got noisier. I figure that noisy one is an exhaust at 014 that should be set smaller, and perhaps I already erred on that one even looser.
 
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