Adjusting solid lifters
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==Mechanical Lifters== | ==Mechanical Lifters== | ||
| − | + | In many cases (refer to manufacturer's instructions if there's a question) the hot lash setting may be used for initial start-up. After the engine is hot, the valves get lashed correctly. 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 pretty close. | |
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| + | {{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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| + | ===OHC vs. OHV=== | ||
| + | The main difference between an OHC and an OHV engine as far as lash goes, is the bucket and shim OHC engines tend to change less between hot and cold. OHC engines w/followers will change a bit more, but still less than a pushrod engine. Because all engines are different, be sure to use this as a guide only. Checking what your engine does is important because of the variables involved. | ||
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| + | One real good piece of advice I was given that I'd like to pass on, is to take the thing you hate doing the most and make it the thing you do the best. | ||
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| + | On a SBC and most other V8s, you can cut the center out of an old valve cover to use when setting lash hot, engine running. It will keep most of the oil from splashing out. You would use 45 degree bent feelers (or bend them yourself), and if you use polylocs, using a valve adjusting tool like shown below can make things easier. A tool like that can even help when setting the lash cold because it's easier to get the same 'feel' from valve to valve. | ||
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| + | [[File:Valve adjus tool.jpg]] | ||
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| + | A go/no-go feeler set is not expensive and will make checking the lash ''uber'' easy. Use a standard feeler gauge for adjustment, not the go/no-go feelers. | ||
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| + | [[File:Go-no go valve feeler.jpg]] | ||
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| + | ==Info from Crane:== | ||
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.) | 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.) | ||
| − | 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.) | + | The amount of valve lash can vary between camshaft profile designs, being as small as 0.010" on some and as great as 0.035" 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.) |
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. | 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. | ||
| − | + | ;Compensating for a Cold Engine when Adjusting Valve Lash | |
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. | 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. | ||
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. | 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. | ||
| − | + | [[File:Crane lash table.jpg|center]] | |
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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. | 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 | |
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. | 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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# 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. | # 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. | ||
| − | + | ;Using Valve Lash to Help Tune the Engine (aka "lash loop") | |
| + | Ideally, the cam- if selected carefully- should be right when using the manufacturer's recommendations for lash and phasing (advance/retard vs. the crankshaft). But if there have been changes made to the engine or the cam isn't ideal, using a "Lash Loop" will point you in the direction the engine needs when replacing the cam. | ||
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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. | 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. | ||
| − | 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". | + | 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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| + | ==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! | ||
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| + | 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, 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. | ||
===What if the valve lash is not known?=== | ===What if the valve lash is not known?=== | ||
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:*[[Determining top dead center]] | :*[[Determining top dead center]] | ||
:*[[How to make a timing tape]] | :*[[How to make a timing tape]] | ||
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[[Category:Adjust valves]] | [[Category:Adjust valves]] | ||
[[Category:Camshaft]] | [[Category:Camshaft]] | ||
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[[Category:Ford]] | [[Category:Ford]] | ||
[[Category:MOPAR]] | [[Category:MOPAR]] | ||
[[Category:AMC]] | [[Category:AMC]] | ||
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