Pushrods? l am dumb as stick.
#1
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Location: Iowa
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Pushrods? l am dumb as stick.
I have a length measuring tool but dont know what to do with it. I have a factory lq9 block,ls7 lifters, and ls3 heads. I ordered lunati 7.4 pushrods and just discovered that i should have measured first. I set the measure to 0 lash pulled it out and compared it to the 7.4 pushrod. It is exactly 1/8 of a inch shorter than the 7.4 pushrod. I dont know what it all means. If you figure in preload which i dont know how to do it seams like these 7.4s mag work after all?
#3
Ok so to measure you need to make sure the cam is on the base circle aka. the cylinder is at TDC....so then you unscrew the tool a few turns, put it in and put the rocker in and torque it to spec (22ft-lb if I remember correctly). The rocker should be able to wiggle side to side a little, while not being able to tap up and down when you are at 0 lash. If the rocker taps up and down open the tool up another turn, if it doesn't wiggle sided to side back it down a turn.
Then the math comes in. If you tool is the same as mine the base measurement will be 6.8" So you take 6.8 + (#of turns * 0.05) = 0 Lash measurment. Then you just add in how much preload you want, in many cases it is around .05-.07".....
In my case I got 16 full turns out of my measurement tool to get 0 lash so I did 6.8+16*.05=7.6" then I added 0.05" preload to get a 7.650" pushrods...
I hope you can follow my method and I hope it helps.
Then the math comes in. If you tool is the same as mine the base measurement will be 6.8" So you take 6.8 + (#of turns * 0.05) = 0 Lash measurment. Then you just add in how much preload you want, in many cases it is around .05-.07".....
In my case I got 16 full turns out of my measurement tool to get 0 lash so I did 6.8+16*.05=7.6" then I added 0.05" preload to get a 7.650" pushrods...
I hope you can follow my method and I hope it helps.
#4
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Andrew
#5
TECH Fanatic
You can also use the Exhaust Opening/ Intake Closing (EO/IC) method to find the base circle of the camshaft. Usually, I'll use EO/IC and TDC on the combustion cycle just to verify my measurements.
For EO/IC, put a pushrod on the exhaust side of the cylinder you are working on and make sure the lifter is contacting the camshaft. Then, rotate the engine by hand until the exhaust lifter starts to raise, indicating that the exhaust valve would be opening at this point. The intake valve is now on the base circle of the camshaft and you can now use your measuring tool to find the desired pushrod length.
What I do is put some teflon tape on the threads of the tool so that it doesn't spin so freely. Then, I just play with the length until I get to zero lash, where the rocker just snugs up to the tool without compressing the lifter when I hit 22 ft/lbs on the torque wrench. You can determine zero lash by wiggling the tool as you tighten the rocker bolt and feeling everything snug up as your wrench achieves 22 ft/lbs. Then, I unbolt the rocker, pull out the tool without turning it, and measure it with my 8" digital calipers. I take that length and add my desired preload.
For EO/IC, put a pushrod on the exhaust side of the cylinder you are working on and make sure the lifter is contacting the camshaft. Then, rotate the engine by hand until the exhaust lifter starts to raise, indicating that the exhaust valve would be opening at this point. The intake valve is now on the base circle of the camshaft and you can now use your measuring tool to find the desired pushrod length.
What I do is put some teflon tape on the threads of the tool so that it doesn't spin so freely. Then, I just play with the length until I get to zero lash, where the rocker just snugs up to the tool without compressing the lifter when I hit 22 ft/lbs on the torque wrench. You can determine zero lash by wiggling the tool as you tighten the rocker bolt and feeling everything snug up as your wrench achieves 22 ft/lbs. Then, I unbolt the rocker, pull out the tool without turning it, and measure it with my 8" digital calipers. I take that length and add my desired preload.