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I'm scratching my head with this one. I've done quite a bit of reading this morning and all the info I gathered tells me to just torque the rockers to spec (17- 23 ft/lbs). The rockers are pedestal mounted so there's no "real adjustment" needed other than tightening them down.
I have a 95 with a bad engine shudder and an exhaust note that sounds like a cylinder isn't firing. I did a compression test and found #2 is dead flat while the other 5 are pumping to 170 PSI. I pulled the valve cover and found everything to be in order, all valves are functioning while cranking the engine. I pulled the rockers for cylinder #2 and nothing is broken or cracked. I put the rockers back on and just finger tightened the bolts. Just for grins I checked the compression before torquing the bolts and cylinder #2 now pumps up to 170 PSI. I set #2 to TDC and then torqued the rocker bolts and noticed the valves get pushed open when tightening. I then re-check the compression and it's dead flat again. So I go back to finger tight and it's back to 170. I was thinking a lifter issue but... intermixed with the testing of cylinder #2 I pulled the intake rocker of #3 and now that cylinder is having the exact same issue.
I'm at a lost on where to go next. I would have said it's the lifters for #2 but #3 was fine before I pulled the intake rocker. Do the lifters need to be bled out to "reset" them if you pull the pressure of them?
Was this a good running engine and problem just occurred? Was there just some engine work done like valve job or head gasket replacement? Does it have inner and outer valve springs? If yes could there be a broken inner you can't see on #2
Very critical that any lifter or push rod or rocker ***'y that is going to disassembled be kept together to be put back in the respective position they came from.
The strength of the valve springs should be able to push the plunger in the lifter body down to it's proper running position while the engine is running. Did you let it idle a minute or two to allow that to happen? The valve springs have to force the oil from the lifter. Cold engine may take longer depending on oil used
Truck was brought to me in this condition so I have no info on it's history. Truck has 100K on it and everything appears original, but no way for me to know. I haven't taken too much apart yet but will be sure to keep everything organized if it comes to that. I haven't run the engine since pulling the valve cover and discovering I can make cylinder #2 pump up. I'm at the point of trying to get the rocker bolts properly torqued AND have proper compression in the cylinders before putting it all back together. I haven't inspected inner springs so I'll go do that now. Cylinder #3 intake is still a mystery though, because that cylinder pumped up fine to 170 before I pulled the intake rocker. Now it's in the same situation as cylinder #2.
No inner springs on any of the valves. Cylinder #3 can be taken out of the mix. I torqued it down to spec and now it's compressing properly to 170 PSI. While I was down there I tried re-torquing both intake and exhaust on Cylinder #2 but no compression (zero). I then tried torquing just the intake rocker for #2, keeping the exhaust finger tight and no compression. Then I swapped and torqued the exhaust rocker and made the intake finger tight and no compression. I went back to both intake and exhaust to be finger tight and get 170 PSI compression.
Because you have no history. If you have access to a shop manual, there is a procedure whereby you compress the lifter so the plunger is at the bottom of the lifter body, it forces all oil out of lifter so it is collapsed. Now the engine has to be in a certain position for, probably a group of valves. Then turn engine for another group. With lifter collapsed and holding it collapsed, you measure the clearance between rocker and valve stem. There is a min/max spec. There were .060 longer and shorter than stock push rods to put in which ever way to get you into the spec window.
Just testing what you have now will tell you if you have a problem in regards to this. You may have make a tool with a lever that grabs the rocker so you can push down to collapse the lifter. Again, no history, a valve job would have remove material from seats, valve face, resurfacing the head would all contribute to closing the spec gap and possibly put the plunger at the bottom and hold valves open. But why on 1 cylinder? I don't know.
I pulled the lifters for #2 this morning and found the bottom of the intake lifter is CHEWED UP bad. It's a concave dish and the lifter stands like the Leaning Tower Of Pizza when placed on the table. I suspect the cam lobe is in no better shape. I'm going to put 2 new lifters in for #2 and see what happens.
Be sure the new lifters are install collapsed, plunger bottomed out. Measure the gap at the valve stem. Then crank it over without starting the engine to add oil pressure to close the gap. The idea is the piston / plunger starts out near the middle of it travel.
The lifters are self adjusting, but that really just means the plunger moves one way, up, to close the gap.
So if you create a gap by loosing a rocker, then add oil pressure the plunger moves up and stays there, and then the valve never fully closes after you tighten the rocker back down.
If you left valve spring pressure pushing down on the lifter plunger it would bleed down, but it might take a week or so as the ball check valve is not suppose to leak down.
Thanks guys, I appreciate all the input. I put everything back together and started it up. I'ts running smooth and quiet with lots of power and acceleration. But.... I'm getting a nice trail of blue smoke under acceleration. I don't see any at idle and don't think I see any while cruising, jut while accelerating. From a stop, stomp the pedal, tires break loose and lots of blue smoke. Cruising at 35 and stomp the accelerator it shift down smooth, takes off and leaves a trail of blue smoke. Valve seals?
Show and tell time. Can you spot the bad lifter? I ended up replacing cylinder #3 too.
I agree, cam is no doubt chewed up too. If I can clear up the blue smoke then we'll replace the cam and all the lifters. If I can not clear it up then it will probably become a full engine rebuild. I noticed the upper intake plenum was very oily so I'm going to start with replacing the PCV valve to see if that clears up the smoke. It's an easy place to start versus replacing valve seals. Any other suggestions are welcomed
Well, to my amazement the blue smoke issue was as simple as replacing the PCV valve. Changed it this morning and I couldn't get it to smoke no matter how hard I stomped the pedal. Looks like I'll be replacing a cam and lifter set soon. One last question: The engine takes about 3 full seconds of cranking before it starts. Not excessive but I'd like to hear it fire off a little quicker. Is there a sensor I should look at? When I put things back together I put on new plugs, wires, cap and rotor.
My 78 , my 50 , and my 53 light off if you breath on the key ....
My 04 takes a few . 3 seconds ain't bad . But check fuel pressure and pressure bleed down . Set timing properly .
During start, the computer doesn't know where the engine is in it's cycle, until the wide window passes by the hall sensor in the distributor.
AFAIK, nothing can be done with it.
I looked at using this wide gap as sync for my VEMS, but it (or was it I?) wasn't smrt enough to use it. I eventually installed a magnet on the rotor, and a hall sensor in the distributor...
