Adjusting solid lifters
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| − | ==Mechanical | + | ==Mechanical lifters== |
| − | In many cases | + | *In many cases the hot lash setting may be used for initial start-up unless the manufacturer's instructions say to do otherwise. If there's any question as to what cold lash to use for start up, refer to manufacturer's instructions. |
| + | *After the engine is hot, the valves get adjusted to their correct hot lash setting. *Then after a '''complete''' cool-down (overnight is preferred), the lash is remeasured and recorded for future use when checking/setting the lash ''cold''. That will get it '''right''' as opposed to ''close''. | ||
{{Note1}}Expect the lash to tighten on a new cam and lifters (not a lot, but noticeable) until the valve train is bedded in together. Once this is done, you'll not be needing to adjust the lash very often, although you still need to occasionally check the lash. | {{Note1}}Expect the lash to tighten on a new cam and lifters (not a lot, but noticeable) until the valve train is bedded in together. Once this is done, you'll not be needing to adjust the lash very often, although you still need to occasionally check the lash. | ||
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[[File:Crane lash table.jpg|center]] | [[File:Crane lash table.jpg|center]] | ||
| − | Remember this correction adjustment is approximate and is only meant to get you close for the initial start up of the engine. After the engine is warmed up to its proper operating temperature range, you must go back and reset all the valves to the proper "hot" valve lash settings. | + | {{Note1}}Remember this correction adjustment is approximate and is only meant to get you close for the initial start up of the engine. After the engine is warmed up to its proper operating temperature range, you must go back and reset all the valves to the proper "hot" valve lash settings. |
;Setting Valve Lash on Mechanical Cams | ;Setting Valve Lash on Mechanical Cams | ||
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This shows the engine a smaller cam with slightly less actual running duration and lift. You can use this method on a trial basis to see what the engine responds to and keep the setting that works the best. Just remember, the more lash you run, the noisier the valve train will be. If the clearance is excessive it can be harsh on the other valve train components. Therefore, for prolonged running of the engine we do not recommend increasing the amount of hot lash by more than +0.004" from the recommended setting. Nor do we recommend decreasing the hot lash by more than -0.008". | This shows the engine a smaller cam with slightly less actual running duration and lift. You can use this method on a trial basis to see what the engine responds to and keep the setting that works the best. Just remember, the more lash you run, the noisier the valve train will be. If the clearance is excessive it can be harsh on the other valve train components. Therefore, for prolonged running of the engine we do not recommend increasing the amount of hot lash by more than +0.004" from the recommended setting. Nor do we recommend decreasing the hot lash by more than -0.008". | ||
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| + | {{Warning}}<br> | ||
| + | "Tight Lash" camshafts cannot deviate from the recommended hot lash setting by more than +0.002" ''increase'', or -0.004" ''decrease''. "Tight Lash" cams are those which have recommended valve settings of only 0.010", 0.012", or 0.014" on the specification card. These lobe designs have very short clearance ramps and cannot tolerate any increase in the recommended valve lash. The extra clearance can cause severe damage to valve train components. | ||
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| + | With "Tight Lash" cams, we recommend using only the prescribed amount of hot valve lash, and that close inspection of the engine be maintained. Please realize that changing valve lash settings from the recommended design specifications will change the harmonic characteristics of the valve train, possibly causing valve spring deterioration and breakage. | ||
==Deviation from recommended lash settings== | ==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! | 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 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 | + | '''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. |
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| + | 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?=== | ===What if the valve lash is not known?=== | ||
In the cases where the cam is unknown and proper measurements impossible, the following may help: | 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". 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! | |
| − | + | *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. | |
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==Resources== | ==Resources== | ||
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