Editing Adjusting solid lifters (section)
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==Deviation from recommended lash settings== How much you can safely deviate from the recommended lash settings depends on a few things. If you are using a solid cam that recommends </= 0.015" hot lash, you should not add more than 0.002" (two thousandths '''''looser'''''), or subtract more than 0.004" (four thousandths '''''tighter'''''). This is because of the lobe ramp shape- if you add even a little too much, the lifter hits the lobe away from the clearance ramp and will 'dig in', causing excessive wear in short time. Cams having bigger lash recommendations can go up to double the lash settings above '''''in most cases''''', but be aware that there are many variations in how any particular engine is designed and built. These variations can have a direct influence on how much difference there is between hot and cold lash settings, and for how much you can "get away with" when going outside the manufacturer's recommendations! '''Too tight is by far the lesser evil than too loose''', as far as if you're going to make a mistake. Too tight will be apparent by a loss of power caused by the valves not seating and can overheat the valve because of a too-short seat time that doesn't allow the valve to transfer heat into the head seat. But too loose will beat hell out of the cam and lifter as well as the rest of the valve train, because the take up ramp has been removed from the lobe. The acceleration will be too great for the valve train to be able to control; as much as a 40% increase in velocity has been seen with a lash setting just 0.002" past the end of the cam's take up ramp! ===What if the valve lash is not known?=== In the cases where the cam is unknown and proper measurements impossible, the following may help: *If the engine is running normally, take both cold and hot lash readings. Those reading will obviously be close to the correct lash for that cam and engine. *If nothing is known about the cam and the engine isn't running, and the unknown cam has to be used, regardless- set the valves cold to 0.016" for an iron head and block engine. 0.016" is used because it's basically at the top of the "tight lash" range, and at the bottom of an old-school cam's wider settings. What you do NOT want to do is set the lash too loose! If you have aluminum heads, go 0.004" to 0.006" tighter on the cold lash. *Most cams have an ID engraved or stamped into them, often on the back end of the cam. The lift and duration @ 0.050" can also be measured if the equipment to degree the cam is available. *Most cam manufacturers will actually recommend setting (hot) lash on an unknown camshaft to .020/.020, and since you would be setting the lash cold in most instances, a very safe bet is to set the lash to .015/.015 for the initial start up. Assuming that there are no issues with the valve train and engine is running correctly. A lash loop can be performed to find the optimal setting for the camshaft.
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