Pushrods and Lifter Bleed Down
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Intermediate
Joined: Sep 2005
Posts: 36
Likes: 1
Pushrods and Lifter Bleed Down
Everything I read about setting up adjustable pushrods says to adjust to zero lash, then lengthen the pushrod according to the manufacturer's instructions and then *wait* for the lifter to bleed down.
So what causes the lifter to pump up in the first place? My engine has been torn apart for weeks because I am changing cams (and still waiting for parts) and installing new adjsutable pushrods.The lifters are installed and I do not plan to remove them from their bores. So is there residual oil inside the lifter making it necessary to wait for the lifters to bleed down in my case even if the engine has been sitting for a long time? How would the installation differ if I installed brand new lifters?
Thanks
So what causes the lifter to pump up in the first place? My engine has been torn apart for weeks because I am changing cams (and still waiting for parts) and installing new adjsutable pushrods.The lifters are installed and I do not plan to remove them from their bores. So is there residual oil inside the lifter making it necessary to wait for the lifters to bleed down in my case even if the engine has been sitting for a long time? How would the installation differ if I installed brand new lifters?
Thanks
Road Warrior
Joined: Dec 2006
Posts: 1,530
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From: Diamond Bar, California
RE: Pushrods and Lifter Bleed Down
If you installed new lifters, you would probably put some oil on them to prelube them.
So the install would be similar.
the reason you wait to move to the next cylinder is because you cant compress a liquid, (basic physics), and as your adjusting your pushrod, you are opening your valves aswell. So after you lenthen the pushrods, you need to wait for the lifters to push the oil out of there bodies and alow the valve to close. If you dont wait 20 min. or so you will like bend the valve as you rotate the engine over to the next cylinder.
So the install would be similar.
the reason you wait to move to the next cylinder is because you cant compress a liquid, (basic physics), and as your adjusting your pushrod, you are opening your valves aswell. So after you lenthen the pushrods, you need to wait for the lifters to push the oil out of there bodies and alow the valve to close. If you dont wait 20 min. or so you will like bend the valve as you rotate the engine over to the next cylinder.
Outstanding HDF Member
Joined: May 2006
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RE: Pushrods and Lifter Bleed Down
lifters are hydraulic so you can adjust them with zero lash. by installing to manufacture specs, say 3 full turns after zero lash, prevents lifter noise. this is why you don't need to do periodic lifter adjustments as you would with solid lifters. Bleed down is the release of fluid in the lifter. Turning the engine over after installing new lifters and adjusting allows the lifter to bleed down. otherwise it takes about ten minutes for a primed lifter to bleed down after adjustment. You did prime them before installing?
Thread Starter
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Intermediate
Joined: Sep 2005
Posts: 36
Likes: 1
RE: Pushrods and Lifter Bleed Down
The lifters are not new and have not been removed. They have been sitting in their bores doing nothing for a while. So are they still primed or have they release their fluid over time is the basic question.
Road Captain
Joined: Nov 2007
Posts: 504
Likes: 2
From: NE IOWA
RE: Pushrods and Lifter Bleed Down
I am so glad you don't have to wait for each hydro lifter to bleed down on a SB Chevy after you adjust the valves would never make the feature race if you changed the adjustment. I must be very lucky because we keep the lifters in oil drop them in the motor preload them turn motor over to get to the bottom of the lobe drop next one in if two are doing it we will do two at a time till done no waiting for bleed down. (I just don't understand)
Road Master
Joined: Jan 2006
Posts: 1,192
Likes: 4
From: Columbus, OH
RE: Pushrods and Lifter Bleed Down
Letting the lifter bleed down is to make sure you have zero lashBEFORE making the final adjustment. It's to make absolutely sure your pushrod is long enough to keep in constant contact with the rocker. I think waiting a few minutes to make sure it's bleed down is better than trashing your engine. I did two or three cycles just to make sure I had zero lash dialed before doing the final adjustment just to be on the safe side.
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Road Master
Joined: Apr 2006
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RE: Pushrods and Lifter Bleed Down
Turning the engine over after installing new lifters and adjusting allows the lifter to bleed down.
VicW.
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