Do the lifters in our L98's actually "pump up" or is this a term that's a hold back from earlier days?

 

Any hydraulic lifter will "pump up" if the valves float. Valve float, by definition, is loss of valve spring pressure on the valve train; which will allow oil pressure to push the lifter's push rod seat out to take up the "false" slack.

TPI however, will usually effectively prevent the engine from ever reaching RPMs where this will happen, even with crappy weak stock springs and heavy stock valves, except in the case of deliberate abuse.

 

sofawhat do you call it with solid lifters or overhead cam

 

Valve float

 

So only with valve float.

So I shouldn't worry about the lifters pumping up on my initial startup after the rebuild. Non-issue.

 

Usually its the oposite way around. New or empty hydrolic lifters will tap like hell for the first few minutes untill theyve had a chance to pump up and take up the excess lash.

 

What the....
Okay. I'm close to starting my new engine. I have a quench of .039. So it's gonna be close. Stock length pushrods, 1.6 rockers. The lifters are original and were soaked in oil for 8 days before I installed them. However, it's been 2 months since I put them in the block. I've set a basic lash for each valve only to finger tight as i'll be setting final lash when it's running.
My question is, am I going to hit valves on pistons when I fire this bad boy up?

 

Soaking them in oil may cause pump up at cold temps as teh oil cant immediatly exit the lifter. You might want to turn the motor over a couple of times to collapse them. Theyll refill on their own after a few minutes of operation, and if you set the lash ahead of time, theyll go silent. BTW, did you measure your valve to piston clearances? How close is it?

As for the lash, you can also set the lash on each cylinder individially with the engine off. IIRC, set the intake when the exhaust just starts to open/set the exhaust when the intake has just closed. This insures that the lifter is on the base circle of the cam when you adjust the lash. This is also easier then trying to hear the tap over a loud engine or many lifters tapping at once.

 

This is how I did set lash. I always set final with it running. I'll make it tap and then adjust from there.

I did not check the piston to valve clearance. Should've but didn't. All I know for sure at the moment is that I can turn it over by hand with no contact.