Post by bedbug on Aug 30, 2014 22:24:03 GMT
If,you're reassembling an engine with worn valves , or the heads or block have been skimmed, you need a way to adjust and correct the preload on the lifters. One way this can done is to use roller rocker, or group b competition rockers, they are adjustable too. Another is to use shim pieces under the rocker posts or pedestals to extend the distance a whole rocker assembly away.
The big advantage of using a threaded adjustment for setting up the preload is the required distance to be set can be done by using the TPI , of the thread rather than using a go - no go gauge. The thread for the push rods is 5.5 thou per flat , as the thread is 30 TPI so a complete turn is 33.3 thou, so 5.5 thou per flat, five flats from making contact is 27.5 thou.
These push rods are a very economical solution for getting individual preload right. There is some doubt cast over there reliability and ability to handle the stresses of hi lift race cams, stronger springs and increased rocker ratio's but in engines that are not maxed out they have worked fine for me.
Checking the length of the new pushrods and some old standard ones.will help you assess approximately, what length your pushrods need to be, If you have skimmed the heads. Had the seats reworked, new valves or different seats installed, block decked etc.etc they will be too long.
Here's how to shorten the pushrods If they are too long, when there's no adjustment left.
Unscrew the threaded end, take the unthreaded ball end out out. Clamp the whole length of the pushrod in a vice between two bits of soft wood. Cable tie a bag over the end of the push rod to catch the pressed in ball end when it flies out. With, the pushrod horizontal in the vice, running left to right across the jaws, insert a piece of steel rod into it that stick out of the end. Whack it with a hammer to drive the unthreaded end out.
If the push rods need to be shortened, the internal step may need to be drilled a little deeper or the ball end you drove out may not sit back in there properly. .
If make have made them too short or attempt to shorten the threaded end ! You may not be left with enough thread engagement to hold the threaded end together. Additional stress could lead to fatigue and failure later on, if too much thread is exposed.
Here's how to install / set them up.
Instal all the pushrods fully retracted and slowly rotate the engine by hand to make sure none of the valves make contact with the pistons.
With a cam followers on the base circles of the cam adjust the push rod so that there's is contact, but zero preload present.
When the preload is right, there should be between 20 & 60 thou clearance between the plunger and retaining clip in the top of the lifter. The smaller you set this preload, the more accommodating your valve train will as the valves settle back into their seats. The trade off, it may also degrade the top end performance .
When you do up the lock nut , be sure the ball or push rod do it rotate with the nut and alter your preload.
Now the preload is set, you need to check for contact or lock up again and / or binging springs. rotate the engine again, twice.
The big advantage of using a threaded adjustment for setting up the preload is the required distance to be set can be done by using the TPI , of the thread rather than using a go - no go gauge. The thread for the push rods is 5.5 thou per flat , as the thread is 30 TPI so a complete turn is 33.3 thou, so 5.5 thou per flat, five flats from making contact is 27.5 thou.
These push rods are a very economical solution for getting individual preload right. There is some doubt cast over there reliability and ability to handle the stresses of hi lift race cams, stronger springs and increased rocker ratio's but in engines that are not maxed out they have worked fine for me.
Checking the length of the new pushrods and some old standard ones.will help you assess approximately, what length your pushrods need to be, If you have skimmed the heads. Had the seats reworked, new valves or different seats installed, block decked etc.etc they will be too long.
Here's how to shorten the pushrods If they are too long, when there's no adjustment left.
Unscrew the threaded end, take the unthreaded ball end out out. Clamp the whole length of the pushrod in a vice between two bits of soft wood. Cable tie a bag over the end of the push rod to catch the pressed in ball end when it flies out. With, the pushrod horizontal in the vice, running left to right across the jaws, insert a piece of steel rod into it that stick out of the end. Whack it with a hammer to drive the unthreaded end out.
If the push rods need to be shortened, the internal step may need to be drilled a little deeper or the ball end you drove out may not sit back in there properly. .
If make have made them too short or attempt to shorten the threaded end ! You may not be left with enough thread engagement to hold the threaded end together. Additional stress could lead to fatigue and failure later on, if too much thread is exposed.
Here's how to install / set them up.
Instal all the pushrods fully retracted and slowly rotate the engine by hand to make sure none of the valves make contact with the pistons.
With a cam followers on the base circles of the cam adjust the push rod so that there's is contact, but zero preload present.
When the preload is right, there should be between 20 & 60 thou clearance between the plunger and retaining clip in the top of the lifter. The smaller you set this preload, the more accommodating your valve train will as the valves settle back into their seats. The trade off, it may also degrade the top end performance .
When you do up the lock nut , be sure the ball or push rod do it rotate with the nut and alter your preload.
Now the preload is set, you need to check for contact or lock up again and / or binging springs. rotate the engine again, twice.