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ok to start with let me give a description of the car.91 sentra ser , 97 fwd blacktop avenir engine,stock maf#22680-54c01 i have installed a gt28 rs , walbro 255 never installed my denso 550's. just put the ecu in that came with the engine to do a startup(will have jim wolf soon).started up ran idled kind of rough but when the electric fan would kick on it would start loping like crazy and die ,so i unhooked the maf big diff. it would surge a little but it idled pretty good and the fan did not affect it.well i left the cars side that night to sleep a little,got to it the next morning and it sound like a suburua when i started it so i pull the v.c and the rocker arm was off from the intake side of the #4 cylinder how does this happen sitting in the driveway at a idle??so i put the rocker back in place instlled both shims rocker arm locked in shims held 175 psi on that cyl. so back to trying to get this thing running right , well i never could get it tyo idle right with the maf so i give up for a couple of hours same thing wouldnt start so i pull the #4 spark plug and it is soaked i pull the v.c and is is the same thing exact same rocker arm. is there any way my fuel pump could be causing this,my #4 cylinder also has gas standing in it.BUT WHY WOULD THE ROCKER BE COMING OFF????????????

WAASSSUUUPPPPP!! The only thing I could find is that if the valvespring retainer clip isn't seated right this will happen and that they are a pita to get seated right. We can pressurize the #4 cylinder to keep the valves from falling down into the cylinder and use a valve spring compressor tool to try to get it seated just right? I think that head has been worked what about you?

i have read that air in the hydraulic lifter will cause this is there any truth to this?any input would be very helpful

Honestly the only thing I've ever heard about rocker arms taking a vacation has been from repeated high-rev usage.

Air in the system could cause erratic changes in hydraulic pressure, so that's certainly a logical conclusion as well.

i did pull all of my lifters out and bleed theme, as of now i am on day #4 since i have bleed them and all is good at the moment , here is a pic of the head before i installed the motor ,everything appeared to be fine and it started fisrt time it rolled over but as it sit overnight apparently the lifter would bleed down due to air . stock avenir ecu waiting on jwt ecu

jbart423 wrote: i did pull all of my lifters out and bleed theme, as of now i am on day #4 since i have bleed them and all is good at the moment , here is a pic of the head before i installed the motor ,everything appeared to be fine and it started fisrt time it rolled over but as it sit overnight apparently the lifter would bleed down due to air . stock avenir ecu waiting on jwt ecu

update in the past 2 days the #4 intake rocker has thrown 2 times and the #2 has thrown 1 time

The rocker arms are throwing because your shims are not setup correctly.

You need the Special service tool to match the shims.

Can get it here:http://www.rpsport.net

Here is a dl to the manual on how it workshttp://www.rpsport.net/support...s.pdf

John

Similar problem. Put new rocker arm and new hydraulic lash adjuster in and cranked engine several revs (with spark plugs out) to build up oil pressure and the new rocker arm popped right out. Noticed that the #4 intake valve was STUCK IN THE DOWN POSITION. That is why the rocker arm came off. It was not in the down position when I first took the valve cover off.
Had nothing to lose so I pried the valve to the closed position, with considerable difficulty. It was stuck pretty good. Squirted some light oil on the stem. Put the rocker arm back in, cranked the engine for a while. Valve did not stick down again so I put everything back together. Engine started and ran fine. That was about 3 weeks ago. Added some Seafoam to the gas and an oil treatment to the oil. Started and ran the engine several times since then.
Yesterday started the egine and the problem sounded as if it was back. This afternoon, took the valve cover off and both the #4 intake and exhaust rocker arms have come off. For me this has always happened when starting the engine, not when the engine was running, so I think that the cause is the valves sticking cold from a buildup on the stem. In my car, a valve job would cost several times more than the car is worth, so I am just going to squirt some Kroil on the valve stems and try again.