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Ls valve train questions.

This is a discussion on Ls valve train questions. within the Internal Engine forums, part of the LSx Technical Help Section category; Hey guys! new to the forums and generally new to the Ls motor, gotta few questions ive researched and just ...

  1. #1
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    black and Gold
    1995 nissan 240sx

    Ls valve train questions.

    Hey guys!
    new to the forums and generally new to the Ls motor, gotta few questions ive researched and just havent found what i needed.

    ok so background on motor it is a iron 5.3 lm7 block from a 2003 avalanche. I had the block bored to factory ls1 3.898" it has complete forged rotating assembly clevite 77 bearings all arp hardware gm ls9 head gasket, ported ls1 heads, oem ls1 lifters oem ls1 pushrods oem ls1 rockers oem valves and springs. 2000 Corvette 12560968 .500/.500 198/209 115.5 112/119 this is cam in the motor for now ( going big single turbo after motor is broke in and boost cam will come with that).


    ok so my question is with my block being the 5.3l and the rest of the parts being ls1 do i have incorrect pushrods in my engine? the reason i wonder this is because i installed the rockers the other day and i did the procedure both of the ways i know which are IC/EO and the GM way of firing position of cyl 1 and blah blah blah..( im sure you know this procedure. and when torqing some of them down i noticed valves started to open, so then i loosened all back up and did the IC/EO procedure i got it to work correctly on all but one rocker arm i believe it was number 6 intake. when cam is on base circle i have very very slight side to side movement on all other rocker arms ( no up and down unless i force the lifter to move) but on 6 intake it has ZERO side to side and it seems like i cant push the lifter down as far as the other ones.

    this has me very confused on why only one is having this problem. engine is on a stand and turns over very easy and makes compression. any ideas would be appreciated im chalking it up to a lifter problem but i dont want to tear back down as motor is like 95% assembled

    Thanks in advance if any of it confuses you ask away and ill try to clear it up

  2. #2
    Spaz is My Mentor SMWS6TA's Avatar
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    Navy Blue Metallic
    98 T/A w/a little mods...

    Here is a thread on how to properly measure for pushrods. You should do this anytime you change the valve train geometry like milling the heads, change lifters, etc.

    Even compressed gasket width can effect the measurements.

    How to Measuring for Correct Push Rod Length.

    Were the heads milled? Leveled? Did they come with the block and if they did are they on the same side they came off?

    Was the block cylinder surface leveled?

    I ask because all of these effect the valve train geometry.

    Other possibilities:
    Rocker - anything unusual? Excess or no play with the bearings? I recommend because of your future plans getting the Compcams Trunion upgrade for those rockers. I have it for my 403ci and they are way better then the stock stuff. Plus it's cheaper then new aftermarket rockers.
    Bad valve spring - You will have to measure it without tension and under compression.
    Bent valve - You should be able to see if bent.
    Bent pushrod - roll them across a mirror. That's the best method of seeing if they are bent.
    Bad lifter - hard to tell unless you tear them down or something is obvious.
    Cam has wiped a lobe - doubt this because you would know while it was out.
    If heads or block was resurface (milled) or new pistons to the block, you should also check for PTV (Piston to Valve) clearance.

    Rocker bolt may also have debris or bad thread. Check it...You could also swap a different rocker to see if it goes ok. Also have the rocker you pulled try it in another position.

  3. #3
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    I checked every thing before i put the engine together and they all seemed fine.
    i did have the deck and heads skimmed just to true them up perfect. .001" taken off heads .002" taken from block. Im going to move the rocker arm and see of the problem follows.

  4. #4
    So any update with that? does the problem still exist?

  5. #5
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    black and Gold
    1995 nissan 240sx

    Going to take the problem rocker off today after work and swap it to see what happens. I will update as soon as I can later today

  6. #6
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    hey guys finally got around to working on the motor a little bit this weekend and got some good progress done on her. I also fixed the rocker arm problem, i loosened all of my rockers and did the ole trustworthy method of IC/EO and torqued and rechecked and all had very little side to side and no up and down unless i forced lifter. im guessing when i did it the factory method i tightened it to much and it was just to tight. but i also ordered the push rod length measurement one, and found that stock ones should work fine for me i guess i got lucky there. i am more toward the higher side of preload though. when the car gets turboed a big turbo cam is going in and a full valvetrain up grade as well so theyll only have to last like a year at most in the engine.

  7. #7
    Senior Member Naaman's Avatar
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    98 Z28 Vert M6

    Glad to see things worked out. I hope it all comes together the way you envision it.
    Lid, Throttle Body, LS6 Intake, Heads, Cam, Magnaflow, LS7 Clutch, SFCs, STB, Panhard Bar, Strano Springs, Hollow Sway Bars, Poly/Roto LCAs, Konis, MGW Shifter

  8. #8
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    black and Gold
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    Thank you sir she's coming along decent can't wait to drive the car next year, engine is now basically done just have to do accessories now.

  9. #9
    Senior Member Naaman's Avatar
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    Cayanne
    98 Z28 Vert M6

    Your build is quite different than mine, so take this with a grain of salt:

    The one accessory I see that you might want to look into is a timing chain. The LS2 timing chain is what I have, and seems to be a popular solution for built motors (mine has less than 400 at the wheels, though... not sure if you need something different for more powerful engines).

    Are you running this motor in a Silvia?

  10. #10
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    black and Gold
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    I went with a billet double roller timing chain and a Melling high volume pump. Stuff it behind stock cover as well. I looked into the ls2 setup but decided against it. Thank you for your input though!

  11. #11
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    black and Gold
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    Sorry I missed your bottom question yes it's going into a 95 240sx.
    SMWS6TA and Naaman like this.

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