Lifters solid vs. squishy & preload measurment?
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Lifters solid vs. squishy & preload measurment? All,
I'm currently going through a pushrod preload measurement with a dial guage with my new 347 setup (with GM LSX lifters). They were solid when I started the process but after several go rounds the have bled down some and have become squishy.
My question is regarding whether the lifter plungers are fully extended (without pushing on them the slightest bit) even when the lifters are squishy? If not, then my preload numbers will be reading a little high.
Bottom line, anyone know if the plungers for the stock lifters will fully extend by themselves while sitting on the base circle?
TIA,
Richard
I'm currently going through a pushrod preload measurement with a dial guage with my new 347 setup (with GM LSX lifters). They were solid when I started the process but after several go rounds the have bled down some and have become squishy.
My question is regarding whether the lifter plungers are fully extended (without pushing on them the slightest bit) even when the lifters are squishy? If not, then my preload numbers will be reading a little high.
Bottom line, anyone know if the plungers for the stock lifters will fully extend by themselves while sitting on the base circle?
TIA,
Richard
A new lifter's plunger will always be very easy to depress but will always push back (spring back) to the top when not loaded with the pushrod/rocker arm. You can "feel" when the plunger starts to depress if you take your time....measure with an adjustable pushrod till you get zero lash (or just the slightest amount of perceptible "play")....remove pushrod, measure, and add the desired amount of preload depth your set-up requires or is recommended.
Even a used lifter after you depress it a few times will also become easy to depress its plunger and you have to be careful that you haven't depressed it when doing all your mock-up and checking.....I usually install a solid roller lifter for checking my piston to valve and camshaft degreeing....no worries about the plunger screwing up your measurements...
Good luck,
Tony
Even a used lifter after you depress it a few times will also become easy to depress its plunger and you have to be careful that you haven't depressed it when doing all your mock-up and checking.....I usually install a solid roller lifter for checking my piston to valve and camshaft degreeing....no worries about the plunger screwing up your measurements...
Good luck,
Tony
Thread Starter
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From: Austin, Texas
Originally Posted by Tony Mamo @ AFR
A new lifter's plunger will always be very easy to depress but will always push back (spring back) to the top when not loaded with the pushrod/rocker arm. You can "feel" when the plunger starts to depress if you take your time....measure with an adjustable pushrod till you get zero lash (or just the slightest amount of perceptible "play")....remove pushrod, measure, and add the desired amount of preload depth your set-up requires or is recommended.
Even a used lifter after you depress it a few times will also become easy to depress its plunger and you have to be careful that you haven't depressed it when doing all your mock-up and checking.....I usually install a solid roller lifter for checking my piston to valve and camshaft degreeing....no worries about the plunger screwing up your measurements...
Good luck,
Tony
Even a used lifter after you depress it a few times will also become easy to depress its plunger and you have to be careful that you haven't depressed it when doing all your mock-up and checking.....I usually install a solid roller lifter for checking my piston to valve and camshaft degreeing....no worries about the plunger screwing up your measurements...
Good luck,
Tony
Last edited by PewterC5-2000; Jan 7, 2007 at 08:51 PM.
Thread Starter
Teching In
Joined: Nov 2004
Posts: 39
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From: Austin, Texas
One additional question....just to make sure I don't have my head up my ****. Intake and exhaust pushrod preloads are measured with the valves on the base circle (i.e. absolutely no lift), right? Some previous statements about TDC have me a little confused, i.e. it seems that anywhere on the base circle would work.
