Has anyone heard of there being a oil pressure relief valve in each cylinder head to control oil pressure to the rockers and lifters? This is for the 3.2 SOHC V6.

THAT IS CORRECT ,THERE IS ONE ON EACH CYL HEAD TO CONTROL THE OIL PRESSURE IN THE LIFTER GALLEY , WHEN IT OPENS IT JUST DUMPS OIL BACK INTO THE CYL HEAD TO DRAIN BACK INTO THE BLOCK , IF YOU REMOVE THE VLV CVR, AT THE
END OF THE CYL HEAD , ONE ON EACH BANK, THERE IS A LITTLE VLV THAT IS 10 A MM HEX , ALLMOST LOOKS LIKE A SMALL BOLT ON EACH SIDE BUT ON OPPOSITE ENDS OF THE CYL HEAD FOR EACH BANK, THE LAST TWO ENGS I ASSEMBLED I REMOVE THEM AND SCREWED IN A SOLID PLUG , SO THAT THE ROCKERS AND THE LIFTERS RECEIVED FULL ENG PRESSURE, SO FAR 2 YRS AND NO APPARENT PROBLEMS , HAVE NOT TRIED THIS ON AN ENG WITH A LOT OF MILES ,BUT WOULD BE INTERESTED IN DOING SO, TO SEE IF THE INCREASE IN OIL PRESSURE WOULD MAYBE QUIETEN DOWN THE LIFTERS , JERRY

That is interesting info. I read a bullitin that said if the lifters were not staying pumped up and/or the rocker shafts were worn then the oil pressure relief valve was probably stuck open. I'd never heard of this valve. I replaced the lifters on my 97' Rodeo only to hear the same lifter noise as before. I also noticed when cleaning the rockers and shafts that the shafts were worn. So I guess I'll be pulling those valve covers back off and checking out that valve.
My motor has 111K miles on it. Do you think plugging the hole would be risking causing another problem?

AS LONG AS THE REST OF THE ENG IS IN GOOD SHAPE I DONT THINK YOU SHOULD HAVE A PROB, BY TAKING THE VLV OUT AND PLUGGING THE HOLE , ALL YOU ARE DOING SUPPLYING THE ROCKER AND LIFTERS WITH WHATEVER OIL PRESSURE THE ENG IS PRODUCING , AFTER THE OIL EXITS THE LIFTER AND ROCKER ARMS IT IS RETURNED TO THE CRANK CASE ANYWAY . , WHAT YOU WILL NEED IS A SMALL METRIC PIPE PLUG THAT IS ALLMOST THE SAME SIZE AS A 1/8 IN STANDARD PIPE PLUG, I USED THE ONES THAT NORMALLY GO IN THE SIDE OF THE BLOCK ON A 2.6 OIL PASSAGE THEY USE ABOUT A 5MM HEX WRENCH ,THE LAST TWO ENGS THAT I DID WERE JUST TOP END WORK, WITH JUST A VLV JOB AND THAT WAS OVER TWO YEARS AGO AND THEY ARE BOTH DOING WELL AND ABSOLUTELY NO VLV TRAIN NOISE JERRY

I hope Monday to tear it apart. I looked in the Hayne's manual for some pics of the heads with the covers off. I didn't remember seeing anything when I had it apart before. I think I seen what you were talking about. Was right in front of the rocker shaft. Stuck up maybe 1/2 -3/4 inch. a friend is going to see what he can find out on All Data. I'll post the results when I'm done. Did you use any thread lock or sealer on the plugs?

NO THE THREADS ARE A TAPER FIT JUST LIKE ALL PIPE THREADS , JUST DONT OVERTIGHTEN IT , JERRY

is it just me or does this look like it may be the holy grail to fix all of our ticking engines im very interested in doing this but just looking at my valve covers it looks like a HUGE pain to pull them with the driver side having the brake booster is there an easy way im not seeing ?

NOPE IT ISNT , IF THE LIFTERS ARE ALL READY CLOGGED UP WITH OILY SLUDGE , REMOVING THE OIL REGULATORS MAY NOT DO ANYTHING AT ALL , BUT IT MAY CORRECT IT, IT IS DEFINATELY WORTH A TRY, WHEN YOU GET THE UPPER PLENUM CHAMBER OFF YOU SHOULD BE ABLE TO MANEUVER THE VLV CVR ENOUGH TO REMOVE IT . JERRY

verrry interesting....
here's my question. what was the design/engineering rationale for these pressure relief valves in the first place? i can see from the oil circulation schematic what the psi's parameters are at a few locations, including for this valve, but it doesn't help me understand.

i'm thinking they wanted to limit the amount of pressure reaching the hydraulic lifters. is this still not a valid reason to retain them? or is it unnecessary overkill?
also, could the increased pressure affect the cam bearings etc in any negative way?

thanks.

here's the parts illustration from the online isuzu parts site looking forward to hearing how this works out for you. www.myisuzuparts.com they are #34



//bc

Well, I got the vlv cover off. Found the OPR Valve. Removed it for inspection. Looked to me it was stopped completely up. I wouldn't say it was letting any oil pressure bleed off at all. I cleened it up. Sprayed it out with carb cleaner which free'd up the plunger inside.Maybe this one isn't in good working order but I'm having trouble figuring how it works. Looks to me that if the oil pressure pushed the plunger up the plunger actually blocks the bleed off holes. Assuming it was stopped up as it appeared I would think I was getting full pressure. If that's the case then I believe that my worn rocker shafts are letting the oil run out from under the rocker arms instead of pushing the oil through the oil holes to the lifters. Also what I found out on All Data supports this as well. There is a tech bulliten for the ORP Relief valve. Also for the rocker shafts and rockers. I'm beginnig to think the only way to cure my lifter noise is to replace the shafts and arms $$$.I believe if I don't do that I will plug the hole for the OPR Valve and try running a heavier oil or additive to try to compensate for the wear. All suggestions welcome.