Nissan Lifter (HLA) Question

So hopefully someone out there has some more in depth knowledge of Nissan hydraulic lash adjusters than I do. 

If SR20 lifters get air in them they must be removed from the engine and placed in a container of oil and manually primed by actuating the plunger manually.  Once they are primed and you put them back in the engine the plunger is rock solid and cannot be depressed by hand.  (standard procedure per FSM)

So here is the question:  If the plunger is already pumped up to the maximum height why doesn't this cause the valve to be held open like on an incorrectly adjusted manual lash adjuster?  The reason I'm questioning this is that I am replacing one lifter that doesn't seem to be acting right with an aftermarket replacement lifter.  The overall height of the replacement lifter when the plunger is extended is .040 taller than the original and I am concerned this would cause an issue. (compressed length is the same)

I'm not an expert on HLAs, but my first thought would be the valve spring pressure is considerably higher than what you can achieve by hand, so it is likely the HLA is getting compressed when it is in the engine.  Does seem a bit odd that the aftermarket lifter is taller.  Is it taller than just the one you are replacing, or taller than all of them?

In reply to eastsideTim :

I didn't measure all of the original lifters, but I did check a second one and both originals were the same height. The stationary body of the replacement lifter is the same height, it's just the moveable part that extends further than the original.

Even when hand pumped you can compress them a little bit, you can do this in a vice if you are careful. If it was pumped up higher than your base circle with oil pressure, and then another cam with larger base circle was run, it would do as you say and hang the valve open. You can remedy this by having each lifter sit 30min at full lift, it will bleed down a little and allow them back up once they see pressure again.

In reply to Paul_VR6 (Forum Supporter) :

So as long as I assemble it and then let it sit for a while before starting the engine the lifters should compress to the correct height? 

I have ruined motors before by not doing this, so I let every lifter sit at full lift for 30mins prior to firing. 

I'd wager that the oem lifters aren't fully pumped up and the replacement is. You'll know when you start it if it were holding a valve open. 
 

unless you're running Bigger cams I would pretty much guarantee that you can't get p2v interference with .040". 

Why aftermarket?  Especially if you're just changing one?

My knowledge of HLA's is limited to changing one out on the F2 in my '89 Mazda 626.  I bought it at the dealer for maybe 40 bucks?  Job went well.  Fixed the problem.  Engine was running great when I sold her at 170k+ miles.

In reply to 1988RedT2 :

I would have gone to the junkyard and picked up a handful of them, but SR20's are getting a little hard to come by in the local self serve yards around here and oem prices have gone up on SR20 parts. I went with aftermarket because I could get a whole set for not much more than a single lifter from the dealer. I also didn't know how many lifters I would find not working right when I pulled the valve cover. Oh, and it is a Challenge car also, so it is debatable if this would be eligible for an unforeseen repair exemption or if I'll have to put it in the budget.