Maximum Lash Ramp Rate?

Small Block Mopar Engine

  1. nm9stheham

    nm9stheham Well-Known Member

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    Just looking for data points here. The question is what is the maximum acceptable lash closure rate rate (or lobe velocity) for when a solid lifter lash is taken up on the valve opening. This would also the rate for when the valve closes.) This would be measured in inches per degree.

    I have a reference here that says up to .001" per degree is OK. How to Determine Lash

    And if you care to know, I am having some fits with some hydraulic lifters on another engine, and am thinking of putting solids in. I have profiled the cam in detail, and know the lobe velocity in detail. So I think I am fine (it is an old cam design with slooow initial and final ramps), but am just looking for any other data points on this. Tnx.
     
    Last edited: Jun 21, 2020
  2. RustyRatRod

    RustyRatRod Bla de blizhibliz de blatde blizi bla bla FABO Gold Member

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    lol
     
  3. rumblefish360

    rumblefish360 So close, yet so far away FABO Gold Member

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    I went threw 3 sets of lifters back and forth with Summit Racing who was way cool about the matter. The last set had 9 of the Hyd. lifters that would not budge, like they were a solid lift.
    I took them apart, reseated the internal spring and they now work fine.
     
  4. nm9stheham

    nm9stheham Well-Known Member

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    That is a lot to put up with RF! That is poor manufacturing work.

    Yeah, the problems seem to be getting gradually worse. The hydraulics I have are showing excessive leak-down on some of them. You stop the engine, wait 5 minutes and 1-2 of them will leak down all the way if they stopped with their valve open. And 1 of those will not pump up.

    They are regrinds on the bodies, which I have no problem with, but I think whoever is doing them is not properly matching the plunger OD to the body ID at re-assembly. That clearance is all over the map from .0001" to .0010" or a bit more, out of a set of 8. I found an old book reference where they talked about sorting the plungers into size bins by plunger OD, and then matching the plunger and body to keep a clearance around .0003". It is on page 87 here: Big-Block Chevy Performance

    So that is the frustration. I think that a lot of the knowledge in these parts has been lost or thrown out as time has gone by and the prior generation of manufacturers has departed the scene.
     
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