Adjusting solid lifters
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 Adjusting lash
Note: Expect the lash to change on a new cam and lifters (not a lot, but noticeable) until the valve train is bedded in together. Once this is done, you won't need to adjust the lash very often, although you still need to occasionally check it. A good time to check the lash is at oil change intervals or before competition.
 Manufacturer's cold adjustment/first start up recommendations
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.
- 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 are to be adjusted to their correct hot lash setting.
- Then after a complete cool-down (overnight is good), the lash is remeasured and recorded for future use when checking/setting the lash cold. That will get it right as opposed to close.
 Comp Cams
- Setting Solid Lifter Valve Lash
Consult the cam spec card for the correct lash specification. All COMP Cams® spec cards list the “hot” (operating temperature) lash setting, but it will also work for initial start-up.
The same basic adjustment procedure (as used with hydraulic lifters) should be used for mechanical lifter cams. Instead of lifter preload, you must use the clearance specs on the cam card for your cam.
Also see Info from Crane.
To adjust VALVE LASH ON MECHANICAL (solid) LIFTER CAMS, follow the same basic procedure as above (adjust with lifter on base circle of cam). Instead of hydraulic lifter pre-load and zero lash, use the valve lash specs printed on your Lunati cam spec card.
- 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. *Using feeler gauges bent at a 45 degree angle (you can bend them yourself) will often make adjustments easier.
- 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.
- 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. The two sizes on one blade are usually 0.002" apart so the first, thinner section will fit but the thicker step shouldn't if the valve is in adjustment.
 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.)
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.
 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.
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.
Note: 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.
- Return to Manufacturer's cold adjustment, above.
 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.
- When the engine is hot (at operating temperature) remove the valve covers and pick the cylinder that you are going to adjust.
- 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.)
- 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.
- 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.
- 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.
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 +0.004" from the recommended setting. Nor do we recommend decreasing the hot lash by more than -0.008".
 Tight lash warning
"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.
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
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.
 Special instructions for Duntov 30-30 cam
- Crankshaft Coalition Wiki articles