Re: Measuring for pushrods
[Re: 6PAX]
#3127358
03/07/23 06:40 PM
03/07/23 06:40 PM
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Joined: Sep 2014
Posts: 4,457 Washington
madscientist
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master
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Posts: 4,457
Washington
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As I have mentioned in another post, I had originally installed a solid lifter cam in my new motor (still on the stand, never run) and have since changed my mind and decided to go with a milder hydraulic cam which is now installed. I had originally measured for and bought new 3/8" push rods for the solid cam that were 8.425" in length. I'm not sure as I don't have the rocker arms installed yet but I suspect they may be too long for the hydraulic cam so I likely will need to remeasure again for new pushrods. However, I need my memory refreshed on the measuring process. I have a set of adjustable pushrods to use for measuring. This is what I was planning to do. Set the roller of the rocker arm so it is resting on the valve stem. Have the rocker arm adjuster set so that approx. 1 1/2 threads are sticking out of the arm. Have the intake and exhaust lifters setting on the base circle of the cam. Insert adjustable pushrod and adjust it so it is snug in the rocker arm cup to where you can still turn it with your fingers. Take out the adjustable pushrod and measure it then add .030 to allow for hydraulic preload. Does this sound right? I add .060 but .030 will work. If you bought Smith Brothers or Trend pushrods they will shorten them for you. They may do another brand of pushrod but I’m not sure about that. You’d have to call and ask. It’s cheaper to shorten them than to buy new.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: Measuring for pushrods
[Re: 6PAX]
#3127391
03/07/23 09:02 PM
03/07/23 09:02 PM
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Joined: Oct 2007
Posts: 4,213 New York
polyspheric
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New York
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How much preload do the lifters need?
Boffin Emeritus
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Re: Measuring for pushrods
[Re: 6PAX]
#3127420
03/07/23 11:38 PM
03/07/23 11:38 PM
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Joined: Aug 2003
Posts: 43,364 Bend,OR USA
Cab_Burge
I Win
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I Win
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Bend,OR USA
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Last edited by Cab_Burge; 03/07/23 11:40 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Measuring for pushrods
[Re: polyspheric]
#3127525
03/08/23 02:39 PM
03/08/23 02:39 PM
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Joined: Jan 2003
Posts: 5,665 Detroit area
6PAX
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How much preload do the lifters need? The instructions that came with the cam (Lunati) say this for adjustable rocker arms (no specific number mentioned): On engines with shaft-mounted adjustable rocker arms, we recommend fully backing off all adjusters prior to installing the rocker shaft assembly. Be sure the pushrods are properly “seated” in the lifters and rocker arms before starting your adjustment procedure. NOTE: Improper adjustment of the rocker arms can cause the valve to hit the piston upon engine rotation! On hydraulic lifter cams, rotate the engine in the normal direction of rotation until the exhaust valve begins to open. At this point, adjust the intake valve to ZERO LASH with no pre-load at the lifter, then tighten 1/2 more turn. Rotate the engine again until the intake valve has fully opened. Now you can adjust the exhaust valve to ZERO LASH, then 1/2 more turn. Repeat this procedure until each cylinder is completed. But they do specify an actual amount of preload for non-adjustable rocker arms: On engines with non-adjustable rocker arms, you must have a lifter pre-load of .020” to .060”.
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Re: Measuring for pushrods
[Re: 6PAX]
#3127526
03/08/23 02:43 PM
03/08/23 02:43 PM
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Joined: Oct 2005
Posts: 8,928 Ontario, Canada
Stanton
Don't question me!
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Don't question me!
Joined: Oct 2005
Posts: 8,928
Ontario, Canada
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But they do specify an actual amount of preload for non-adjustable rocker arms:
On engines with non-adjustable rocker arms, you must have a lifter pre-load of .020” to .060”. I'd hardly call a range of .040" "specific" !!!
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Re: Measuring for pushrods
[Re: 6PAX]
#3130790
03/20/23 11:54 AM
03/20/23 11:54 AM
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Joined: May 2019
Posts: 714 Lake Villa Il
INTMD8
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super stock
Joined: May 2019
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Lake Villa Il
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You did this as well correct?
"rotate the engine in the normal direction of rotation until the exhaust valve begins to open. At this point, adjust the intake valve to ZERO LASH with no pre-load at the lifter, then tighten 1/2 more turn. Rotate the engine again until the intake valve has fully opened. Now you can adjust the exhaust valve to ZERO LASH, then 1/2 more turn. Repeat this procedure until each cylinder is completed."
69 Charger. 438ci Gen2 hemi. Flex fuel. Holley HP efi. 650rwhp @7250 510rwtq @5700
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Re: Measuring for pushrods
[Re: 6PAX]
#3130928
03/20/23 07:31 PM
03/20/23 07:31 PM
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Joined: Aug 2003
Posts: 43,364 Bend,OR USA
Cab_Burge
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I Win
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Bend,OR USA
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I did it in the order in this chart. Forget that 40 yr. od GM chart Use the new, better, correct method describe above on the valves opening and closing . This works well on 1.5 ratio rockers, I use 1/10 to 1/3 turn preload (depending on iron or aluminum heads) on 1.6 or higher ration rockers on hydraulic lifters You can also use the piston at top dead center method on the firing stroke also Another thing to consider is the adjuster diameter and thread count, the 3/8x24 adjusters have .042 adjuster movement for one full turn, the 7/16x20 adjusters have .050 per thread movement 1/2 turn on the 3/8 adjusters is .022 preload, 1/2 turn on the 7/16 is .025 the devils is in the details
Last edited by Cab_Burge; 03/20/23 07:36 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Measuring for pushrods
[Re: INTMD8]
#3131174
03/21/23 05:12 PM
03/21/23 05:12 PM
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Joined: Jan 2003
Posts: 5,665 Detroit area
6PAX
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You did this as well correct?
"rotate the engine in the normal direction of rotation until the exhaust valve begins to open. At this point, adjust the intake valve to ZERO LASH with no pre-load at the lifter, then tighten 1/2 more turn. Rotate the engine again until the intake valve has fully opened. Now you can adjust the exhaust valve to ZERO LASH, then 1/2 more turn. Repeat this procedure until each cylinder is completed." I adjusted the rockers that way today and it didn't change anything. For some reason just the one rocker/pushrod combo is different from the rest. When I have the adjuster backed all the way out and the pushrod in place, I can't turn the pushrod with my fingers without the lifter turning slightly as well. If I pull upward on the pushrod very slightly as I am spinning it the lifter stops turning in the bore. So, since it looks like the pushrod is just starting to push down on the lifter plunger without having set any lash, instead of doing the half turn to set the lash I only did a quarter turn.
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