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checking pushrod length

This is a discussion on checking pushrod length within the General Help forums, part of the LSx Technical Help Section category; I have a question about checking pushrod length. I know I need to get the cylinder to TDC before I ...

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    Moderator 98TransAmWs-6's Avatar
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    checking pushrod length

    I have a question about checking pushrod length. I know I need to get the cylinder to TDC before I check the length and you typically do that to cylinder 1 but that head is off atm. My question is what cylinder is TDC the same time as #1? Another question after I measure the length do I add anything for preload and how much for ls7 lifters?
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    Spaz is My Mentor SMWS6TA's Avatar
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    Will I got some info on this, I'll post later when I get to a pc...

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    Quote Originally Posted by SMWS6TA View Post
    Will I got some info on this, I'll post later when I get to a pc...
    Alright thanks Scott. I know how to check its just I need to know what other cylinder on the passenger side is TDC when #1 is TDC since that head is off. I can't put it on just yet since I need to remove the broken lifter bolt.

    I was thinking it is #6 that is TDC when #1 is also.

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    Spaz is My Mentor SMWS6TA's Avatar
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    I got this info passed to me on how to measure for push rods. Does this jive with you?

    Assuming you bought the Comp adjustable pushrod.

    Each turn of the pushrod is 0.050". When fully closed, it is 6.800". This is pushrod "gauge length" so you can't measure it directly as the pushrod length is actually based on the length between the ball ends where the ball end measures 0.140" in diameter. Assuming you are using stock rockers or a non-adjustable rocker with a correctly established wipe pattern (Note, wipe pattern should be established first.)

    1. Open the adjustable pushrod to the same length as your stock pushrods
    2. Close it down two turns
    3. Put your rocker rail on the head
    4. Make sure you cylinder (typically #1) is at top dead center on the firing stroke so both valves would be closed
    5. Put the pushrod in place on the intake valve and make sure it is in the lifter cup
    6. Install the rocker and snug down the bolt (don't need to torque, just make sure it is snug)
    7. Lift rocker tip up and down, if it "ticks" the pushrod is too short. If you can't easily move the rocker the pushrod is too long.
    8. You can try and adjust the pushrod in place buy my fingers are too fat so I end up pulling the rocker and adjusting the pushrod length. Go either shorter or longer 1/2 turn and try again.
    9. You are trying to get to the point where the lifter doesn't "tick tick" with the pushrod in place nor is the rocker snug. When you get the pushrod length such that you just barely get rid of the "tick tick", you have found "zero lash".
    10. When you have found zero lash, carefully remove the rocker and pushrod without rotating the pushrod.
    11. Tighten the pushrod until it is fully closed counting the turns as you go.

    To figure out your pushrod length you do the following. Lets assume it took 10-1/2 turns to close the pushrod down to its shortest length after you reached zero lash. Each turn is 0.050".

    Your length is then: 6.800" (fully closed length) + 10.5 X 0.050" (number of turns times the length change per turn) = pushrod length minus preload. So for this case:

    6.800 +10.5 X 0.050 = 7.325"

    This is the length you measured to zero lash without any lifter preload. Now lets say you want to have 0.075" lifter preload, you add that to the measured number and you end up with 7.400" pushrods.

    Now repeat for the exhaust valve to verify the length. If you have something like Yella Terra's, it is the same procedure but you must snug down the rocker pair rather than the single rocker.

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    Quote Originally Posted by SMWS6TA View Post
    I got this info passed to me on how to measure for push rods. Does this jive with you?

    Assuming you bought the Comp adjustable pushrod.

    Each turn of the pushrod is 0.050". When fully closed, it is 6.800". This is pushrod "gauge length" so you can't measure it directly as the pushrod length is actually based on the length between the ball ends where the ball end measures 0.140" in diameter. Assuming you are using stock rockers or a non-adjustable rocker with a correctly established wipe pattern (Note, wipe pattern should be established first.)

    1. Open the adjustable pushrod to the same length as your stock pushrods
    2. Close it down two turns
    3. Put your rocker rail on the head
    4. Make sure you cylinder (typically #1) is at top dead center on the firing stroke so both valves would be closed
    5. Put the pushrod in place on the intake valve and make sure it is in the lifter cup
    6. Install the rocker and snug down the bolt (don't need to torque, just make sure it is snug)
    7. Lift rocker tip up and down, if it "ticks" the pushrod is too short. If you can't easily move the rocker the pushrod is too long.
    8. You can try and adjust the pushrod in place buy my fingers are too fat so I end up pulling the rocker and adjusting the pushrod length. Go either shorter or longer 1/2 turn and try again.
    9. You are trying to get to the point where the lifter doesn't "tick tick" with the pushrod in place nor is the rocker snug. When you get the pushrod length such that you just barely get rid of the "tick tick", you have found "zero lash".
    10. When you have found zero lash, carefully remove the rocker and pushrod without rotating the pushrod.
    11. Tighten the pushrod until it is fully closed counting the turns as you go.

    To figure out your pushrod length you do the following. Lets assume it took 10-1/2 turns to close the pushrod down to its shortest length after you reached zero lash. Each turn is 0.050".

    Your length is then: 6.800" (fully closed length) + 10.5 X 0.050" (number of turns times the length change per turn) = pushrod length minus preload. So for this case:

    6.800 +10.5 X 0.050 = 7.325"

    This is the length you measured to zero lash without any lifter preload. Now lets say you want to have 0.075" lifter preload, you add that to the measured number and you end up with 7.400" pushrods.

    Now repeat for the exhaust valve to verify the length. If you have something like Yella Terra's, it is the same procedure but you must snug down the rocker pair rather than the single rocker.
    That is correct. I just need to figure out what ls7 lifter preload is. I read. 07 is correct but I am not positive. Then there is the fact I have no clue when any of the passenger side cylinders are tdc and which ones are tdc when the drivers side are. It would be easy after I know which passenger side cylinders are tdc at the same time as a particular cylinder on the drivers side because I can see the cylinders on the drivers side.

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    I found the information I needed on what cylinders are TDC at the same time:

    Cylinders that are 4 positions apart in the order, are at TDC at the same time. #1 & #6, #8 & #5, #4 & #7, and #3 & #2 are at TDC in pairs.

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    1-8-7-2-6-5-4-3.

    Left bank: 1-3-5-7
    Right bank: 2-4-6-8

    So based on 4 apart, you are correct. Where did you find that information at?

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    Quote Originally Posted by 35th-ANV-SS View Post
    1-8-7-2-6-5-4-3.

    Left bank: 1-3-5-7
    Right bank: 2-4-6-8

    So based on 4 apart, you are correct. Where did you find that information at?
    One of the posts here explains it:

    http://www.thirdgen.org/techboard/tech-general-engine/612601-ls1-firing-order-older.html

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    Does anyone have any idea what it means when it says adjust the pushrod until the barely tick goes away? For example is the rocker still supposed to move up and down visibility? I adjusted the pushrod until the rocker didn't really move much but it ticks a tiny bit and the length with preload came out to 7.2625. That just doesn't seem right to me. I know I have 243 heads but they are truck 243 heads. Also when I put the stock pushrod in it seemed to do the same thing. So I am really unsure what the length needs to be.

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    When they say until the tick goes away, they mean move the rocker until there is no more free space between the rocker and pushrod or "zero lash". Add your preload and you have your measurement. Always check more than one cylinder and take the average of the two readings if they are different. I usaully do three cylinders because the mesaurement is bit inaccurate so multiple readings give you better sense of what the length needs to be.

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    Quote Originally Posted by DaddySS View Post
    When they say until the tick goes away, they mean move the rocker until there is no more free space between the rocker and pushrod or "zero lash". Add your preload and you have your measurement. Always check more than one cylinder and take the average of the two readings if they are different. I usaully do three cylinders because the mesaurement is bit inaccurate so multiple readings give you better sense of what the length needs to be.
    Thanks I found a video which explained it and I figured it out. My push rod length came right at 7.4 with ls7 lifters and 243 heads with the stock cam.

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    Spaz is My Mentor SMWS6TA's Avatar
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    What is the preload for LS7 lifters?

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    Quote Originally Posted by SMWS6TA View Post
    What is the preload for LS7 lifters?
    About .075 I believe. Also I typed the wrong length, it is 7.375.
    Last edited by 98TransAmWs-6; 01-12-2013 at 01:27 AM.

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    Spaz is My Mentor SMWS6TA's Avatar
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    Did a quick check (without verifying TDC of the cylinder)


    On the #2 cylinder

    Intake had 9 turns on mine.
    9 x 0.50 = 0.45 + 6.8 + 0.75 = 7.325"

    Exhaust had 9.5 turns

    9.5 x 0.50= 0.475 + 6.8 + 0.75 = 7.35"


    Tomorrow when I have some day light I'll do a proper measurement.


    So for it looks like I have to long of a push rod.

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    Moderator 35th-ANV-SS's Avatar
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    Quote Originally Posted by SMWS6TA View Post
    Intake had 9 turns on mine.
    9 x 0.50 = 0.45 + 6.8 + 0.75 = 7.325"

    Exhaust had 9.5 turns

    9.5 x 0.50= 0.475 + 6.8 + 0.75 = 7.35"
    Assuming you meant 0.05 and not 0.5.

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    Spaz is My Mentor SMWS6TA's Avatar
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    yes it was suppose to be 0.050

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    Question is there a quality difference between Comp Cams and Manley pushrods? The reason I ask is that Comp Cams is about $133 and Manley is $100 on the ws6store for 7.375 pushrods.

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    Not sure, but I went with Manley hardened push rods on my build. No issues to date. They have about 12K miles on them, and I've bounced the limiter maybe 2-3 times in that time period. Shifting out of first is pretty difficult with the Procharger and 4.11 gears

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    Spaz is My Mentor SMWS6TA's Avatar
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    IMHO not much difference, The 7.4" rods I got 3 weeks ago were Manley because they were on sale. Chrome moly is chrome moly.....Also Will I wasn't able to because everytime I tried to go outside it would rain......

    - - - Updated - - -

    Quote Originally Posted by 35th-ANV-SS View Post
    Not sure, but I went with Manley hardened push rods on my build. No issues to date. They have about 12K miles on them, and I've bounced the limiter maybe 2-3 times in that time period. Shifting out of first is pretty difficult with the Procharger and 4.11 gears
    I wish I had those problems.......

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    Quote Originally Posted by SMWS6TA View Post
    IMHO not much difference, The 7.4" rods I got 3 weeks ago were Manley because they were on sale. Chrome moly is chrome moly.....Also Will I wasn't able to because everytime I tried to go outside it would rain......

    - - - Updated - - -

    Quote Originally Posted by 35th-ANV-SS View Post
    Not sure, but I went with Manley hardened push rods on my build. No issues to date. They have about 12K miles on them, and I've bounced the limiter maybe 2-3 times in that time period. Shifting out of first is pretty difficult with the Procharger and 4.11 gears
    I wish I had those problems.......
    Well let me know Scott what measurement you get. I just ordered 7.375 pushrods.

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