Adjusting solid lifters
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==Solid lifters== | ==Solid lifters== | ||
| + | '''From Crane:'''<br> | ||
| + | '''Mechanical Lifters''' | ||
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| + | All pushrod engines using mechanical (solid) lifters, or mechanical roller lifters, must have an adjustable valve train so that precise adjustment for "Valve Lash" can be made to match the camshaft's requirements. Valve lash is the running clearance that exists between the tip of the valve stem and the valves mating surface of the rocker arm. (It is expressed in the Crane Catalog as "Valve Lash" and on the camshaft specification card as "Valve Setting". Both terms mean the same thing.) | ||
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| + | The amount of valve lash can vary between camshaft profile designs, being as small as .010" on some and as great as .035" on others. It is important to use the recommended valve lash when you first test the performance of the engine. You must also be concerned with thermal expansion of the engine components. (This is especially true if using aluminum alloy cylinder heads, or block.) | ||
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| + | For this reason, Crane requires that the valve lash be set with the engine "Hot" on all pushrod engines using mechanical lifters. This will insure that the minimum required clearance (valve lash) is maintained throughout the engine's operating temperature range. | ||
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| + | '''Compensating for a Cold Engine when Adjusting Valve Lash''' | ||
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| + | When installing a new cam, the engine will be cold but the lash specifications are for a hot engine. What are you to do? There is a correction factor that can be used to get close. We mentioned that the alloy of the engine parts can be affected by thermal expansion in different ways, therefore the amount of correction factor to the lash setting depends on whether the cylinder heads and block are made out of cast iron or aluminum. | ||
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| + | You can take the "hot" setting given to you in the catalog or cam specification card and alter it by the following amount to get a "cold" lash setting. | ||
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| + | With iron block and iron heads, add .002" | ||
| + | With iron block and aluminum heads, subtract .006". | ||
| + | With both aluminum block and heads, subtract .012". | ||
| + | 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. | ||
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| + | '''Setting Valve Lash on Mechanical Cams''' | ||
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| + | All the valves must be set individually and only when the lifter is properly located on the base circle of the lobe. At this position the valve is closed and there is no lift taking place. How will you know when the valve you are adjusting is in the proper position with the lifter on the base circle of the cam? This can be accomplished by watching the movement of the valves. | ||
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| + | 1. When the engine is hot (at operating temperature) remove the valve covers and pick the cylinder that you are going to adjust. | ||
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| + | 2. Hand turn the engine in its normal direction of rotation while watching the exhaust valve on that particular cylinder. When the exhaust valve begins to open, stop and adjust that cylinder's intake valve. (Why? Because when the exhaust is just beginning to open, the intake lifter will be on the base circle of the lobe, so the intake is the one we can now adjust.) | ||
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| + | 3. Use a feeler gauge, set to the correct valve lash, and place it between the tip of the valve stem and rocker arm. Adjust until you arrive at the proper setting and lock the adjuster in place. | ||
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| + | 4. After the intake valve has been adjusted, continue to rotate the engine, watching that same intake valve. The intake valve will go to full lift and then begin to close. When the intake is almost closed, stop and adjust the exhaust valve on that particular cylinder. (Again, when we see the intake valve almost closed, we are sure that the exhaust lifter is on the base circle of the lobe.) Use the feeler gauge and follow the procedure described before in step 3. | ||
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| + | 5. Both valves on this cylinder are now adjusted, so move to your next cylinder and follow the same procedure again. In the future you may find shortcuts to this method, but it still remains the best way to do the job correctly. | ||
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| + | '''Using Valve Lash to Help Tune the Engine''' (aka "lash loop") | ||
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| + | The engine only responds to the actual movement of the valves. Since the valve cannot move until all the running clearance (valve lash) has been taken up, the amount of valve lash you use affects the engine's performance. For example, if you decrease the amount of (hot) valve lash, the valve will open slightly sooner, lift higher, and close later. This makes the camshaft look bigger to the engine, because of a slight increase of actual running duration and lift. If you increase the amount of (hot) lash the opposite occurs. The valve will open later, lift less, and close sooner. | ||
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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 +.004" from the recommended setting. Nor do we recommend decreasing the hot lash by more than -.008". | ||
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===Unknown lash recommendations=== | ===Unknown lash recommendations=== | ||
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 is available. It would be really good to know exactly what cam it is so the correct lash settings could be used. One reason for this is tight lash cams have a relatively small window for deviating from the recommended lash settings. But in the cases where the cam is unknown and proper measurements impossible, the following may help: | 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 is available. It would be really good to know exactly what cam it is so the correct lash settings could be used. One reason for this is tight lash cams have a relatively small window for deviating from the recommended lash settings. But in the cases where the cam is unknown and proper measurements impossible, the following may help: | ||
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{{Warning}}<br> | {{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. | "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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