Checking Pushrod Length - Team Camaro Tech
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post #1 of 2 (permalink) Old Oct 15th, 16, 03:51 PM Thread Starter
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Anne
 
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Checking Pushrod Length

Found this at LS1tech. Nice writeup:

Checking Pushrod Length
by 99bluebird

1. Using the EO/IC method, get the lifter to the base circle of the cam.

2. Using a known length pushrod (7.400" is a good start with stock rockers) run the rocker arm bolt down to zero lash. This is easily done with your fingers "wiggling" the rocker, the point at which the "slack" is just gone is zero lash.

3. Set your torque wrench to 22 lb./ft. Tighten the rocker to full torque and count the number of turns it takes to get there. 1 full turn wtih a stock 8mm X 1.25 bolt is ~.047" preload as measured at the pushrod/rocker interface.

4. I normally shoot for 1 1/4 to 1 3/4 turns with stock type lifters like Comp 850's, LS1, LS7 etc.

For an example, if you use a 7.400" pushrod and come up with 3/4 of a turn, you will need at least .025" longer pushrod to get into range. If you end up with 2 1/4 turns, you will need one .025" shorter...

I might not know everything but I will tell you that this method has worked for me year after year cam swap after cam swap. We average 3 cam swaps a week here so you can do the math.

If you are not familiar with the EO/IC method for determining valve events in a 4 stroke engine, its very simple:

For a given cylinder as the Exhaust valve is Opening, the intake lifter will be on the base circle of the cam and lash/preload should be checked for that intake valve.

For a given cylinder as the Intake valve is Closing, the exhaust lifter will be on the base circle of the cam and lash/preload should be checked for that exhaust valve.

THIS METHOD ALWAYS WORKS!!!

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post #2 of 2 (permalink) Old Oct 15th, 16, 04:23 PM
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John
 
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Re: Checking Pushrod Length

Might work but I personally would not rely on this method for checking pushrod length on an LS motor.

I use a pushrod measuring tool. Basically on the LS motor. Mark the top of the valve stem with a felt marker. Bolt the rockers to the heads using the rocker stands or no rocker stands with the LS7.

Rotate the engine by hand 2 full revolutions. Remove the rocker and inspect the pattern to confirm the rocker tip is pushing on the center of the valve stem.


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