Push Rod Length Question with TR224
11-07-2009, 04:13 PM
#1
Push Rod Length Question with TR224 I have the TR224 in my rebuilt ls6. Since it was decked, and so were the heads, and a variety of other things I am going to assume all the dimensions are not the same as factory. Still using new stock lifters.
I have a lot of clicking, especially for a small cam. People complain when they ride in the car. It is consistent for every cylinder.
I bought the comp cams adjustable checker. I have read, when using the zero lash method, to add .080" to your measurement to wind up with the right preload.
If I set the adjustable at 7.350 I can still pull the rocker up off the valve stem. There is a fair amount of gap. If I add .080 to this I would be around a 7.425
If I put the checker at 7.4 it is very tight. If I add .080 to this I would be too high I think.
Logic says that I need to be in the middle at a 7.45 push rod. Is anyone else using ones this long with a mild comp/TR cam? I dont want to buy 7.425s and have them be too short and not fix the problem.
I have a lot of clicking, especially for a small cam. People complain when they ride in the car. It is consistent for every cylinder.
I bought the comp cams adjustable checker. I have read, when using the zero lash method, to add .080" to your measurement to wind up with the right preload.
If I set the adjustable at 7.350 I can still pull the rocker up off the valve stem. There is a fair amount of gap. If I add .080 to this I would be around a 7.425
If I put the checker at 7.4 it is very tight. If I add .080 to this I would be too high I think.
Logic says that I need to be in the middle at a 7.45 push rod. Is anyone else using ones this long with a mild comp/TR cam? I dont want to buy 7.425s and have them be too short and not fix the problem.
11-07-2009, 07:05 PM
#2
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This is the method I used. I noticed that after the lifters set in the motor for about a week they lost the spongy feeling.
FWIW, EVERY cam install I have done using the LS7 lifter with a cam with greater than .600" lift (read smaller base circle) AND stock heads w/GM MLS gaskets has taken 7.425" pushrods for ~.050"-.060" preload. We measure lifter preload on each and every cam install we do. I have never had a lifter failure nor do we end up with the dreaded "sewing machine" noise.
Its very simple, If you change ANY of the following:
valve sizes, valve job, head milling, thinner/thicker head gaskets, decked block, cam with an altered base circle, etc... YOU MUST CHECK FOR PROPER PUSHROD LENGTH.
I have helped countless numbers of individuals with this process over the phone, via email, and PM's. I've posted the process on at least 3 occasions.
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!!!
I hope this helps someone. I have explained it so many times I think I do it in my sleep!!!
Shane
Its very simple, If you change ANY of the following:
valve sizes, valve job, head milling, thinner/thicker head gaskets, decked block, cam with an altered base circle, etc... YOU MUST CHECK FOR PROPER PUSHROD LENGTH.
I have helped countless numbers of individuals with this process over the phone, via email, and PM's. I've posted the process on at least 3 occasions.
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!!!
I hope this helps someone. I have explained it so many times I think I do it in my sleep!!!
Shane
11-12-2009, 04:32 AM
#5
Extend the pushrod until you have zero lash rather then setting a length. Then you can figure out how much preload you will get with each pushrod. The other option, is to contact Terry Mantion with measured pushrod length and order a set of custom pushrods to any length you want. One advantage is you can order 11/32" which a lot of people have been doing to stiffen up the valve train. Terry uses overall length though so you will need to correct your measured numbers.
11-17-2009, 07:03 PM
#6
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using this method i come up with .066 preload for the intake and .054 preload for the exhaust (yes the base circles are different sizes) factoring in a .025 longer pushrod. is this enough preload?
