Ferm and other vortec guys I need help!
 

My 99 tahoe has had what I thought to be some rocker arm noise. I pulled the passenger bank valve cover a month ago and turned the second one back about a quarter turn. That seemed to fix it. It was ran about 3 to 3.5 qts low when I found the remote oil filter lines leaking. Replaced and all has been well or so I thought. The last couple weeks the noise has come back with the cold weather. today I was driving down the road and it started to miss on a cylinder. I came back to the house and got a number 6 cylinder misfire code. I change the spark plugs, cap, rotor, button and wires. #6 was wet with fuel and all others looked good on burn. after all that I still have the miss. New plug is wet like the old one.


I tried to do a compression check and got 75 I think on that cylinder and 100 on the one behind it. This was coil wire off and turning it over at full throttle. I say I "think" 75 because it held once and then after that got only a bouncing needle while having someone else turn the engine over. I'm not a hundred percent sure my gauge is working right and I need to know where to go from here. Could this be in the head or valve train and not a piston/lower block issue? God I hope so. I'm just trying to make it through hunting season and ultimately get another year is out of it to pay off the wife's car and get something newer.


let me know where to go from here....this engine has about 60k on it.when we rebuilt it I replaced everything. ..heads...crank...pistons..rods....etc...etc...

The only other thing i can think to add is in addition to the tapping when starting cold i have heard what i can only describe as a metallic sound similar to an ac compressor clutch going out. It wasn't the ac though it was in that passenger bank valve cover. I'm going to pull the valve cover tomorrow after work but wanted to check in first on what to look for.

recheck with another compression tester, go ahead and pull all the plugs and check compression on all of them

Wet plug and low compression could be a stuck lifter. I've had ALOT of problems out of federal mogul/sealed power lifters. Theres 2 manufacturers out there for lifters for the OEM hydraulic roller cams, FEDERAL MOGUL/SEALED POWER, and MELLINGS. MELLINGS was the OEM manufacturer for these lifters and is all I use in them. Also get a better gauge as the compression should be up around 125-175 depending on engine health. I would remove the valve covers, get ready for a mess, and adjust the valves the old fashioned way. Start it up, let it idle, and back them off until they hammer, then tighten them down till it stops, and go another 1/4 turn. For the cylinder thats wet and throwing the code, start by backing the rockers off a turn on that cylinder and see what that does. And I know the book calls for 1/2-1 turn of preset, but I have had nothing but problems with anything more than a 1/2 turn, so I stick with a 1/4 turn to be safe.

But start with the basics. If it has compression, even only 60 lbs, it should still fire. If the plug is wet, it is either a hung poppet(if your running the old style injectors still) which is flooding the cylinder and washing the rings down, or a valve isn't opening allowing the air fuel in or out. A collapsed lifter could be at fault, but I wouldn't expect to see the wet plug with a collapsed lifter unless it is still cracking open some(just not much).

If all else fails, remove the check valve from the compression tester hose and set it up so tou can use it to pressurize the cylinder. Rotate the engine around to TDC and blow some air into the cylinder. Listen to see if you hear air rushing out the intake, exhaust, crankcase, or if the engine rolls around. You can find a compression leak in a hurry with compressed air.

Thanks guys!

Another possibility is carbon sticking a valve.... Be cautious.... If it IS carbon you can end up w valve piston contact.... Did a head job on Mom's 98 z71 for that very reason.

alright here's where I'm at so far I did the reverse pressure test with my shop air...150psi...number umber 6 at TDC on compression stroke. There was a little air out of the oil fill on the valve cover but the majority came out of my exhaust.

latest development is I pulled the valve cover and have a collapsed lifter. Rocker arm was so loose it was turned sideways and not touching the valve. But that doesn't explain my compression loss through the exhaust. So I'm thinking while I have the intake off inspecting the lifter Journal I'm going to go ahead and pull that head to look for a burnt valve stuck causing the lifter to crush. What do y'all think?

pull the rocker arms and retest. i've seen this twice back when ethanol 1st hit the pumps. the goo in the tanks at the station gummed up the valves which hung them open, and allowed the rocker to kick off. a collapsed lifter normally will not hang a valve open, or cause a rocker to fall off the valve stem. sounds to me like a gummed up valve caused the valve to stick open, and give enough play to allow the rocker to kick off. also, replace the pushrod while your there. i HIGHLY DOUBT a collapsed lifter caused this.

I don't think the lifter cause it either that's what I was trying to say about a possible burnt valve. I was thinking a burnt exhaust valve that stuck closed may have cause the lifter to collapse. You think that could be the root cause....a burnt valve? It would also explain the lost compression?


So you're saying pull the rockers and retest compression?

Carbon build up on the valve stem.... Decarb time.

OR IF the valve already contacted the piston it may be bent.

Had to take a break to gain my sanity. Working on getting down to the intake and getting it off. Dad walked over and checked the push rod and confirmed the lifter has definatly come apart or is trashed. He'sbuild aa lotof small blocks in his day so I'm working on getting down to it now.


I HATE mechanic work!



... side note: I noticed today that if you have grease on your face it bothers everyone around you much more than it bothers you personally.


back at it will report back later if I don't take my own life.

Two bad lifters...on different cylinders. I'm wondering if dirty oil or additives has caused the other failure. I'm bout to pull the head and all the other lifters and check them

If it makes you feel better you aren't alone... I've been hit hard by the plague!
Two engines and a transmission ($4000+) in my diesel dually in 105 miles!!!
Yes you read that right.....
Engine cracked a piston.... Found a replacement and somehow managed to drop a nut into the head during installation.... Made it 100 miles before the nut lodged between a valve and seat..... Repaired engine, two new pistons w rings, one rod, all new rod bearings, a head, head gasket, and head bolts..... For it together and in 5 miles the trans locked up and slid me to a stop.... Been working on this damn truck since August!

Just pulled it out of the shop again tonight.... Have a couple loose ends to tie up and then I'm doing a trans, t-case, and header on the jeep... Then gotta get geared up for a 1000 mile trip to TX for a new job..... Wheeeeeeeee

Post up a picture, but it sounds like SEALED power lifters to me. Had this happen to me twice before I learned my lesson about using them.

Damn ferm I just picked up two new lifters and they are "sealed". should I not use them? What brand do you recommend?

I will oNLY use MELLINGS lifters. I will NEVER use another SEALED POWER hydraulic roller in an aold school VORTEC again. BOTH times I used SEALED POWER I had problems, and both times it was in a 350 with a hydraulic roller cam. AUTOZONE carries MELLINGS, most everybody else carries SEALED POWER. And MELLINGS was the OEM manufacturer for GM for these which is strange considering FEDERAL MOGUL makes many OEM parts.

Well I have my compression back after grinding the valves and putting the head back on. I pulled the other head to be sure since the carbon buildup was so bad on the valve stems. Reworked it and just reinstalled. Calling it a night. Hope to get the intake and everything else back on tomorrow. I'm praying at this point I haven't burned up a lower end bearing since my oil pressure gauge doesn't work. I put a new oil pressure sending unit on today. The needle needs calibrating but it's doing something now at least.

Glad you got it back together. Carbon build up is pretty common on 'city cars' the old phrase "blow the carbon out" actually does have some merit.... Once in a while a few wot 0-60's can help avoid that happening.

if you are not running a cat, add some Yamaha ring free to your gas, it will get rid of any carbon. Its the same thing as techron additive, its cheaper by the treated gallon than techron at the auto parts store

Yeah I drive like a grandpaw and it shows.


Can yall walk me through the timing and valve/rocker arm settings?

Go to #1 TDC, adjust 1/4 turn past zero lash, then 2, 3, 4, etc...etc....right?



Im gonna need that tomorrow and need a refresher.

there are a few different ways to get it done but this is probably the most fool proof way with the engine not running

http://www.centuryperformance.com/va...procedure.html


OR you can do it as mentioned above tho I personally prefer to adjust when not running.

bring it to tdc compression stroke for each cylinder. rotate the pushrod and tighten it down until the slack is taken up, then go an extra 1/4 turn. repeat for each cylinder. if you go in the firing order, then it is only 1/4 turn of the crank to tdc for the next one.

Well, I got her fire up last night. Ran it with valve covers off and got the valves dialed in. Lifters pumped up good and had good pressure.

The only thing I can attribute it to at this point is the HEAVY carbon buildup on the valve stems that must have caused those couple to stick and crush the lifters. I went through both heads and reground them. Its purring like a kitten now. it hasnt been that quiet in some time. The miss is definately gone and its smooth as silk.

I got a few loose ends to button up so I can drive it a couple days. I dont trust it to go 100 miles to hunt this weekend so probably going to ride with my buddy till I can get some more around town miles on it first.