88911coupe

Could someone give me a detailed explantion or diagram on how hydraulic lifters work? I've looked at the diagram of the lifter in Bruce Anderson's book but really can't get a feel for how it exactly works. Also, why does this eliminate the need for valve adjustments? FWIW, I fully comprehend the mechanical system on my '88 but this issue really baffles me.
TIA

Avenger6

Hydraulic pressure pumps up the lifter. Since the pressure is regulated to be constant, the length of the lifter and the force exerted are also constant. It expands in length as needed, so no adjustments are necessary. As I understand, the only possible problem is a failure of the seals, which requires a new lifter.

kkim

Don't know if you've seen this before... some very good info and pictures.

https://rennlist.com/forums/diy-993-1995-1998/197318-lifter-repair-101-a.html

cowtown

Think of the lifter as an automatic version of the little adjustment screw that takes a flathead screwdriver on your '88. Instead of manually measuring clearance and adjusting using a feeler, the lifter uses oil pressure to take up the slack space between the top of the valve stem and the rocker.

88911coupe

Thanks, very helpful!

chris walrod

Kinda like 12 little German mechanics riding along under the valve covers

Avenger6

Just re-read my post. Sort of mis-spoke, since th length IS NOT constant, but adjusts as needed. The constant hydraulic pressure means the pressure exerted is constant. If the adjustment is "loose," the lifter exoands, taking up slack. When it reaches proper length, it can't expand beyond what is "needed" by the rocker, and the pressure releif valve lets the "push back" by the rocker push oil out of the lifter until the lenght is "right" again.

"Knowing" how it works and "explaining" how it works aren't the same thing, especially in my case.