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Iron Head Lifter adjustment

Because the lifters in an Iron Head are solid, Meaning they do not have a hydraulic mechanism in them to take up extra play in the valve train, they need, more maintance then modern hydraulic ones do. These lifters actually the tappets in the lifter bodies should be adjusted whenever you change your oil about every 3000 miles. However, unlike when you drain your oil the engine must be cool during tappet adjustment

Each tappet must be brought to its lowest position for adjustment. This is done on stock cams (aftermarket cam sets come with their own instructions) by rotating the engine in the direction of normal rotation, which is the way it turns when running, until the like lifter in the other cylinder is at its highest point. For example, if you are adjusting the rear intake lifter, the engine is rotated until the front intake lifter is at its highest point.

The 1/2” nut on the top tappet is the cup for the push rod, which is called the tappet adjusting screw in the service manual. The lower nut, a 7/16”, is the tappet adjusting screw locknut, which keeps the adjustment from changing once you set it. Start an adjustment by loosening the locknut and turning the adjustment screw downward into the lifter body until the push rod has noticeable shake. (Shake is when the push rod can be moved freely from side to side in the tappet adjusting screw’s cup.)

Now slowly turn the tappet adjusting screw out of the lifter body, one flat at a time, until almost all shake is removed, but you can still spin the push rod in the cup with no trace of bind using only your finger tips. Once you have it so set, tighten the locknut so the adjustment won’t change. You’ll have to hold the tappet adjusting screw with a wrench to keep it from moving when you cinch down the lock nut. In fact, you should move the adjusting screw one flat to tight, because when you tighten the nut it usually moves the tappet adjusting screw one flat back. Going a little to tight will usually put you right where it needs to be when all is locked down. Then rotate the engine and do the other tappet in the same way. Then go back to the first one you did and recheck it. Continue on until all four tappets have been adjusted and rechecked.

What this does is set the tappet adjustment so when the cam is at its lowest point, the valve it controls can fully close, sealing the cylinder. Although, it also means that the lifter is set as high as possible so the valve will open as much as possible when the cam tells it to. Setting a tappet to tight will hold the valve off its seat when it should be sealed this will cause compression to bleed off when the engine is running. Ok if it’s running.
 


 

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