Hydraulic Valve Lifters
 

Hi Guys,

I'm just about done with a cylinder headreplacement job on my 95 Ford Taurus 3.0 liter V6 vulcan engine. These are brand new cyclinder heads and valves. I have a question about the valve lifters.

AfterI reassembled the rocker arm and push rods, I rotated the engine and checked each rocker arm / pushrod assembly at it's piston's top dead center position where both intake and exhaust valve should be closed. In some cases there did not appear to be any load on the push rod. I could wiggle it a little bit. In other cases, the push rod appeared to be still exerting force on the rocker arm such that I could not wiggle the pushrod. In these cases, when I loosened the rocker arm bolt, I could see the valve spring de-compress. This caused me to be concerned that the valves aren'tgoing closed when they're supposed to.

I'm not sure I understand how the lifters are supposed to work. I read that they are supposed to be "solid" when opening the valve because the lifter's internal check valve keeps the oil from escaping. Asa valve closes,does the check valve open and allow oil to escape so that thevalve spring acting through therocker arm and pushrod cansinkthe lifter internals as deep as necessary into the lifter cylinder?

I really need some guidance here. I don't know if I should continue with re-assembly or not.

Thanks, BC

RE: Hydraulic Valve Lifters
 

Went back to it the next day and it seemed to be okay. At each cylinder'stop dead center position, I could rotate the pushrods. On those valves that were open, I could not rotate the pushrod.

There's no valve adjustment on this engine. I see a spec in my haynes manual that says "Collapsed tappet gap (nominal): .088 to .0189 inches". So, I guess that means if your vlv stem hieght is off a few mills, it will get sucked up by thehydraulic lifter.

The cars all back together now and runs okay. Before I ran the engine, I did a compression check and got145 at the lowest cylinder and 170 at the highest. Will try again with the engine hot.