z240 Posted December 15, 2009 Share Posted December 15, 2009 Well some good information was shared at least. I suspect it would be quite complex to analyze the relative movement with temperature of all of the involved parts to properly understand why hot is more than cold. It is not simple for sure. I was hoping for more geometric analysis and thermal expansion coefficients of various metals being thrown around. I think its cause the cam tower supports grow more 'cause they is aluminuminum, moving the cam up some. 'bout as technical as I can git this early.... Quote Link to comment Share on other sites More sharing options...
NewZed Posted December 15, 2009 Author Share Posted December 15, 2009 That sounds reasonable. It does suggest the possibility that you could adjust the lash hot, then have the motor cool down, the lash get too tight and burn/warp a valve or lose lubrication at the cam lobe. Just a possibility. If you set it cold and you can get your gauge in, the lash will just get bigger as it warms up. Has anyone ever had a fine-running hot motor that developed valve problems after a cold start. I am new to the L6 but didn't Nissan go to hydraulic self-adjusting valve train later? Not to wear the thread out... Quote Link to comment Share on other sites More sharing options...
Apex944 Posted December 16, 2009 Share Posted December 16, 2009 That sounds reasonable. It does suggest the possibility that you could adjust the lash hot, then have the motor cool down, the lash get too tight and burn/warp a valve or lose lubrication at the cam lobe. Just a possibility. If you set it cold and you can get your gauge in, the lash will just get bigger as it warms up. Has anyone ever had a fine-running hot motor that developed valve problems after a cold start. I am new to the L6 but didn't Nissan go to hydraulic self-adjusting valve train later? Not to wear the thread out... I've set my valves when cold everytime, as I have also seen that most companies have their valves adjusted only when engine is cold. Especially in the diesel world, every engine we've adjusted valves on the book calls for the engine to be stone cold. Some manuals even say let it sit overnight and adjust the valves the next day so as the engine is garunteed to be cold. I can also see what your saying about adjusting them when hot and having the possibility of the lash becoming too tight and causing damage to the valvetrain. Although as other's have mentioned their results from checking hot/cold measurements were only off by .001 - .002 max from what theyve seen. What I can see though is the different aftermarket camshafts having different heat expansion rates causing the over tight valve lash possibilty to occur if setting them hot. But hopefully those manufacture's are sending the new lash thickness information with their camshafts to avoid such issue's... Guess I can give it a try sometime in the next week or so... Wouldn't be all that worried if something broke as the engine's hanging on a thread already haha. So, set the valve lash when hot then let it cool, check the lash and record results. Reset the lash cold then get it hot and check the lash while it's hot and then see where it's at when it is cold again. I realize there probably won't be much benefit to doing such work as this but i'm curious myself to see how much the lash is affected when setting it hot and setting it cold. ( Although It's due for an oil change and valve adjustment soon anyways so why not tinker with the valvetrain a little more than normal and see what we can find. ) Quote Link to comment Share on other sites More sharing options...
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