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Do hydraulic lifters 'pump down?

3175375

Well-Known Member
I overheated my Mustang 3 years ago coming home from Knott's.
Pulled the heads (stock) n confirmed burnt valves.

I decided too buy Edelbrock Performer heads, Lunati roller rockers n new pushrods. The car sat for about 18 months before I got it together. Finally got to turn it over n nothing. Confirmed fuel n spark. Ran a compression test n all 8 cylinders had 0 psi.

I have thought about it a bit and maybe this is what has happened:

Car sat so long, lifters pumped down n I adjusted the valves in that state.

When I went to started it they got to normal position n all of the valves won't close causing the 0 compression situation.

Could this be true?
 
Ish. Not all of the valves have pressure on them at the same time, so they wouldn't be inclined to pump down at the same time.

Always adjust valves with the lifters on the base circle of the cam, and preferably at running temp.

Prime the oil pump and verify you're getting oil up to the heads. Try to put a bit of oil in each plug hole to seal the rings. Readjust the valves cold, then run a compression test. If you get pressure, see if it fires. Once it's heated up, readjust the valves and check compression again.
 
Ish. Not all of the valves have pressure on them at the same time, so they wouldn't be inclined to pump down at the same time.

Always adjust valves with the lifters on the base circle of the cam, and preferably at running temp.

Prime the oil pump and verify you're getting oil up to the heads. Try to put a bit of oil in each plug hole to seal the rings. Readjust the valves cold, then run a compression test. If you get pressure, see if it fires. Once it's heated up, readjust the valves and check compression again.
I always rotate the crank n cam to adjust at each Valle's 'zero lash' position.

Only changed the heads.

I think where I erred was not getting oil pressure up before adjusting.

I will re-evaluate
 
hydraulic lifters need to have some "pre-load" as opposed to "lash" or clearance like a solid lifter. The lifters could collapse if the engine hasn't been run in a long time but should pump up pretty quick. When you swapped the heads you would have had the load off the lifters more than enough time for them to come up (they have a spring inside them). Unless they are Rhodes lifters you would set the rockers arm adjustment by tightening until the pushrod gets tight or doesn't spin in your fingers easily. Then you tighten about a half turn more. If you have over tightened the rockers you could reset them by rotating the engine in its normal direction of rotation and watch the exhaust valve on the cylinder you are adjusting. When the exhaust valve begins to open, stop rotating the engine and adjust that cylinder’s intake rocker arm. When the exhaust valve is just beginning to open, the intake lifter will be on the base circle of the lobe. Back off the intake rocker arm nut and remove any tension from the pushrod. Wait a minute or two for that hydraulic lifter to return to a neutral position. The spring inside the lifter will push the pushrod seat up against the retaining lock if you give it enough time to do so. Now spin the intake pushrod with your fingers while tightening down the rocker arm. When you feel a slight resistance to the turning of the pushrod, you are at “Zero Lash”. Tighten the adjusting nut one half turn from that point and it is set. Then hand turn the engine again, watching that same intake. It will go to full open and then begin to close. When it is almost closed, stop rotating the engine and adjust the exhaust rocker arm on that particular cylinder. When the intake is almost closed, that exhaust lifter is on the base circle of the lobe. Loosen the exhaust rocker arm and follow the same procedure you did for the intake.
If the lifter doesn't return to the neutral position with the rocker arm loose (after a couple minutes) then the lifters are shot.
 
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