Did I measure preload correctly, and does this sound correct?
10-30-2009, 01:19 AM
#1
Staging Lane
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Did I measure preload correctly, and does this sound correct? I setup my adjustable pushrod so that when my rockers were torqued to spec, there was almost no play (less than .003 in play).
The measurement was 7.493, then I add my desired preload of .060 which gives us a total of 7.553 so call it 7.550 or 7.575 (which would give ~.057 or .082 preload).
Did I do this correctly? The car is dead cold, has been sitting for weeks. I soaked the lifters in oil a before they went in a few days ago and everything is torqued down.
Second question, does this sound like the proper length pushrod for my setup?
LS2 Block
Stock LS2 Headgaskets
LS7 Lifters
Trickflow 220cc as cast heads (no milling)
Trickflow said I needed a 7.500 pushrod, and my cam card said to use a .025 longer than what I was using, so I was guessing 7.525, but I hear LS7 lifters shorten that amount due to the raised cup in the body, so your opinions?
Thanks!
The measurement was 7.493, then I add my desired preload of .060 which gives us a total of 7.553 so call it 7.550 or 7.575 (which would give ~.057 or .082 preload).
Did I do this correctly? The car is dead cold, has been sitting for weeks. I soaked the lifters in oil a before they went in a few days ago and everything is torqued down.
Second question, does this sound like the proper length pushrod for my setup?
LS2 Block
Stock LS2 Headgaskets
LS7 Lifters
Trickflow 220cc as cast heads (no milling)
Trickflow said I needed a 7.500 pushrod, and my cam card said to use a .025 longer than what I was using, so I was guessing 7.525, but I hear LS7 lifters shorten that amount due to the raised cup in the body, so your opinions?
Thanks!
10-30-2009, 06:14 AM
#2
Nope, try this. Shane from Thunder Racing uses this and I tried it two days ago and checked it against my pushrod length checker and like he says, it works great and its easy.
From Shane
Here it is again in a nutshell:
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!!!
From Shane
Here it is again in a nutshell:
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!!!
