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2004-2007 Cadillac CTS-V Performance Mods Discussion, keep busting rocker arms in Cadillac CTS-V Series Forum - 2004 - 2007; I ended up using a preload of 0.006" on my Morels to get rid of the check engine light. I ...
  1. #16
    heavymetals's Avatar
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    Re: keep busting rocker arms

    I ended up using a preload of 0.006" on my Morels to get rid of the check engine light.

    I had used: 0.050" and 0.025" preload.

    I also used pushrods 7.150".

    Just had to get the plunger off the retaining ring.

    With the RHOADS, I was using 0.050" and no check engine light.

    All lifters are not the same (I learned that one!).

    That is why I use adjustable rockers.

    The only way to "dial in" the engine.

    The lifter itself only has about 0.200" of travel so it doesn't take much to bottom it out.

  2. #17
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    Re: keep busting rocker arms

    Quote Originally Posted by heavymetals View Post
    That is why I use adjustable rockers.

    The only way to "dial in" the engine.
    About this statement, let me ask you this. If I have one intake valve set at 0.060 preload and another intake valve set at 0.070 preload (all else equal) do you believe the lift or duration achieved on these two valves differs by virtue of the different preloads?

  3. #18
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    Re: keep busting rocker arms

    Quote Originally Posted by darkman View Post
    About this statement, let me ask you this. If I have one intake valve set at 0.060 preload and another intake valve set at 0.070 preload (all else equal) do you believe the lift or duration achieved on these two valves differs by virtue of the different preloads?
    They sure do!

    Read this: http://www.rhoadslifters.com/Pages/Installation.html

    The paragraph on "other suggestions".

  4. #19
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    Re: keep busting rocker arms

    Quote Originally Posted by heavymetals View Post
    They sure do!

    Read this: http://www.rhoadslifters.com/Pages/Installation.html

    The paragraph on "other suggestions".
    Okay, I have seen those words before.

    So, if I switch from a cam with a 0.550 inch maximum lift to a cam with a 0.600 inch maximum lift and coincidentally change my preload from 0.100 inch (which is often used for OEM LS lifters) to a preload of 0.050 inch (which also often used fro OEM LS lifters) I actually achieve no increase in valve lift?

  5. #20
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    Re: keep busting rocker arms

    Depends on how the spring pressure from the added lift loads the hydraulics of the lifter.

    As you can see, they are interrelated and it won't be "tit for tat" (hydraulics being non-linear).

    In other words, the same difference in preload from lift will not mean the "slack" is taken up by the lifter.

    Confused?

    A lifter set with 0.100" preload will have an operating range tighter then a lifter set with 0.050" preload.

    Your 0.050" setting will result in less lift because it will have a wider operating range.

  6. #21
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    Re: keep busting rocker arms

    Quote Originally Posted by heavymetals View Post
    Depends on how the spring pressure from the added lift loads the hydraulics of the lifter.

    As you can see, they are interrelated and it won't be "tit for tat" (hydraulics being non-linear).

    In other words, the same differance in preload from lift will not mean the "slack" is taken up by the lifter.

    Confused?

    A lifter set with 0.100" preload will have an operating range tighter then a lifter set with 0.050" preload.

    Your 0.050" setting will result in less then 0.050 difference in lift.
    Okay, so you are saying that oil in a closed chamber is compressable?

  7. #22
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    Re: keep busting rocker arms

    C'mon, I ain't that stupid.

    You are ignoring the lifters spring, which is part of the equation also.

    Less preload = less spring compression = increased operating range.

    If it was just a simple "pump oil into a piston/cylinder" then lifters would pump up to the maximum.

    There is a balance with the hydraulic pressure and spring tension against the valve spring pressure which is offset by preload.

  8. #23
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    Re: keep busting rocker arms

    Quote Originally Posted by heavymetals View Post
    C'mon, I ain't that stupid.

    You are ignoring the lifters spring, which is part of the equation also.

    Less preload = less spring compression = increased operating range.

    If it was just a simple "pump oil into a piston/cylinder" then lifters would pump up to the maximum.

    There is a balance with the hydraulic pressure and spring tension against the valve spring pressure which is offset by preload.
    Well it is not clear to me how the spring is involved once the lifter is filled with oil.

    I am struggling to reconcile the view that preload affects valve events with what I have read in many other places. Specificallly, that as long as a lifter is preloaded to a level within its operating range that there is no differences in valve events stemming from two different preloads. This is allegedly because a low preload simply requires the lifter to contain more oll than a lifter with more preload, but when operating both lifters fill with oil and both preloads ultimately achieve zero lash. I have read many threads where people discuss running more or less preload based on the noise that results, but no one ever suggests that there are performance implications as long as the preload is within the manufacturer's specification.

  9. #24
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    Re: keep busting rocker arms

    I don't know what to tell ya.

    The info is there.

    I repeat: this is why I use adjustable rockers.

    Using your analogy, then it shouldn't matter what the preload is as long as it is within the range of the lifter operation.

    It doesn't, but if you want to set the motor up so all the cylinders are equal, it does.

    And we are talking about within 0.00x" here.

  10. #25
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    Re: keep busting rocker arms

    To the OP.

    What is your oil pressure reading?

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    Re: keep busting rocker arms

    Oh it dropped now. At 80kpa when idling (whatever it is in psi, 11 I think). Typically 280/300 kpa (43 psi) when warmed up.

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    Re: keep busting rocker arms

    History is, 1st rocker was on cylinder one, clean split on the exhaust valve. Second time, cyl 4 and 7 I think. Now, I don't know how many I lost. Pissing rain outside, I'll try to get the valve covers off tomorrow. Pushrods in all cases were true and straight. Thought it was a bad batch given YT had issues last year with a few bad batches. But this is the 3rd set now. Either YT are utter garbage and not suitable for blower cars or something's messed up with the equation. On a side note I am still plagued by an oil consumption issue though I'm not sure if the two are related (likely oil consumption needs a better pcv routing from what I've been told). I could go buy jesels pro rockers, just seems over kill for a car that hardly ever sees redline (thank the sticky monster clutch for that) and doesn't go on the track all that often these days.

  13. #28
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    Re: keep busting rocker arms

    High oil pressure is an indication of excessive preload.

    Mine went from 36(Rhoads lifters) to 52(Morel) at idle (warm & triggered the check engine light) with the preload set at 0.050".

    Decreasing the preload to 0.025" lowered the oil pressure to about 48.

    With the preload set to 0.007" the check engine light went out and oil pressure dropped to around 38.

    Only took about a year to chase down!

  14. #29
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    Re: keep busting rocker arms

    Oil pressure has never been a problem for me. Nor have I ever had a CEL (other than my current one of course) as a result of the lifters.

  15. #30
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    Re: keep busting rocker arms

    You need to check and see if the valve spring retainers are bottoming out on the valve stem seals. That could explain the valvetrain binding and the oil consumption because the seals could be damaged now. I hope this makes sense. I had this happen on a big block chevy years ago but it bent a pushrod and drank oil.

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