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Join Date: Jan 2000
Location: Wilton, Ca. USA
Re: Best way to adjust solid cam
exhaust opening-intake closing method recommended by most cam manufacturers. Here's the idea off of cranes website:
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.
1. When the engine is hot (at operating temperature) remove the valve covers and pick the cylinder that you are going to adjust.
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.)
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.
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.
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.
Using Valve Lash to Help Tune the Engine
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".
"Tight Lash" camshafts cannot deviate from the recommended hot lash setting by more than +.002" increase, or -.004" decrease. "Tight Lash" cams are those which have recommended valve settings of only .010", .012", or .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.