I swapped banks on the coils and i did a compression test before i removed the heads and the psi on the BAD cylinder was 90psi. Now im guessing it was because the valve wasnt closed....ill check on the guides but the valves were held pretty good i had to push on then a bit to get them out but ill check the guids when i get home....do y'all think it could have been a lifter causing this? Im stuck on the cause for this......
Broken Intake Valve from Valve Float 6.2L L92?
- Thread starter t69chevelle
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thompsoj22
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if your heads are good and the inspection proved no mechanical defects than throw a set of lifters at it and put it back together and see what happens. when you did the coil swap your "assuming" the electrical harness connector for that cyl 8 is good, i would make sure it's good. the cyl was absolutely "cold" either from a lack of compression or ignition. run that piston down an inch or two in the cyl and pour a couple ounces of oil on the piston and see if it leaks past the compression rings, if it dosent that is a good sign but does not rule out a broken oil control/scraper ring. i think you would have some marring in the cyl if a ring were bad? the lifters are a shot in the dark, i think with that many miles the cam should be replaced if new lifters were to be installed, factually your efforts have proven cyl 8 missfire but no cause, keep it cheap with "guess parts". simply replace the lifters for that cyl only? put it back together if the fluid leakby test is acceptable, start it and if it still misses leave the plug in the cyl and slave another into the plug wire and ground it, start it and confirm good spark. i know PITA, but the alternative is take it to a shop and spend thousands. also im just "shooting from the hip" consider everyones opinion and hopefully you will "get er done"
When you say "slave another into the plug wire" what do you mean exactly? Jut a plug in the wire and leave it outof the cylinder to see that it throws a spark? If so i somewhat already did that, no the same way but i pulled the wire off the plug and it shot out a good inch of spark while the truck ran with no noticable idle change.
thompsoj22
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yup, ok so the harness is good. i simply cant accept that a lifter could keep a valve open? take the intake and exhaust springs for that cyl to a machine shop and ask if they would measure/compare tension for "free" just to rule out a bad spring "dont mix them up" keep whatever is wrong with 8 isolated to that cyl. if all is good put the heads back on without intake/exhaust manifolds and do a cold leak down compression test and compare to other cyls and it will diagnose if compression is low based upon piston rings,ring landings, do you have a source for compressed air?. lap the valves before install, new stem seals perform a fluid leakby test. you are trying to breath life into an engine with a mechanical defect, you have to find it, fix it and down the road you go! most people just open their wallet and $6,000 dollars later they are driving but they will allways feel the sting of the cash, you are doing the right thing for your "budget" but it is a frustrating PITA. hang in there!
swathdiver
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Would anyone be able to help? I really want to figure out what is causing the issue so i can get my truck on the road again.
Where do you live Johnny? Maybe someone here lives close by and could help in person. If I reread all these posts right, you've got an L92 and the heads are off the block and it looks like a bad exhaust valve on #8, right? How does the piston look? Was it hit? Is the valley cover smooth or bumpy? What do the lifters look like on #8?
Did you send the heads out to get cleaned up and a valve job, did you replace the rockers and springs?
Ill take the springs to get tested and see if there is much of a difference. Unfortunately i dont have access to an air compressor. I havent tried pouring a few oz of oil to see if it seeps past the rings yetsince it has been very cold here lately and i dont have a indoor garage. But hopefully we get a warm day here soon and ill hope on that. Yeah i definetly dont have $6K to throw at it which is why im trying to narrow it down and do most of the legwork. I also dont want to put it back together and then have it keep doing the same thing. I appreciate the positivity!
I live in North East Mississippi. Yes that is correct. The piston looks fine it doesnt look steam cleaned to say it was a headgasket and it doent have any chips or dents in the face of the piston to indicate that the valve hit. No i have not sent the heads out since i want to minimize my spending to only what needs to be replaced. But if i have no other option i will if needed.
randeez
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to me, valve guide/seal and possibly valve seat needs to be cut or atleast lapped in heavily with a new valve (you can buy them individually). but replacing the guide DIY could go wrong quick.
If it were me, i would send them both out to get cleaned up, tell machine shop what the issue was so they have an idea what to look for. looks like both heads are broken down already? high mileage grab a set of blue beehives springs to throw in. have them assemble the heads if you're not confident doing so. new head gaskets, new bolts, and i would be closing the engine back up.
now atleast you know mechanically there isnt an engine issue. perhaps the oil fouled out the plug and thats why it wasnt firing but you could have other issue on that cylinder plug/coil is easy enough to diagnose by swapping between cylinders
If it were me, i would send them both out to get cleaned up, tell machine shop what the issue was so they have an idea what to look for. looks like both heads are broken down already? high mileage grab a set of blue beehives springs to throw in. have them assemble the heads if you're not confident doing so. new head gaskets, new bolts, and i would be closing the engine back up.
now atleast you know mechanically there isnt an engine issue. perhaps the oil fouled out the plug and thats why it wasnt firing but you could have other issue on that cylinder plug/coil is easy enough to diagnose by swapping between cylinders
swathdiver
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I agree with Randy, get a new set of springs and send the heads out a machine shop. Let me know about the lifters and valley cover.
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