@ revhead.. imo a broken spring wouldn’t retract the valve all the way back in causing interference with the exhaust valve and piston. There’snit that much clearance between the plug and valves to begin with. A spring broken in two pieces can rotate into the second half to where it’s not the same height anymore. Plus the compression comes and goes which means there is fluctuations which has to be a moving part. A spun rod bearing won’t cause compression issues and I would also have a knocking sound which I do not and it would also be hitting the plug every single time if it’s going to hit it at all.
Blown cylinder or chain jump?
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@sus-spec cast position and forged eagle rods. If the position was broken I’d be getting a constant miss fire, but I’m not... the miss is very random and it’s once every 5-6 seconds at idle. But in running conditions there’s no miss. And I only get plug contact under mid boost 6-7 psi and at low rpm, don’t need to be high rpm to hit plug. Plus I can go high rpm and it won’t hit the plug if I don’t go into boost. I feel as if the boost is pushing the intake valve open.
The car has been running 18-20 psi for over 5 years. This engine fail just happened recently when I upped my tune and raised the redline point from 6000 rpm to 6300 rpm but who knows man, I mean 18-20 pounds for 5 years on an Apexi AFC is great man. That build lasted a very long time. Maybe it’s just about that time....
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Imo I the cast pistons arent strong enough for that high boost and you could have the ringland breaking apart, thats still enough to hold compression. I see what you are saying tho and that interesting. You can get the tool that holds the valve while the head is on the car so you can pulls springs to check. But still I think if the valve was hitting the piston, it would bend the valve permanently and always have a miss. Doubt its just enough to bend back and forth. Just the fact that the plug is beat all the way around.
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People was having ring land issues back in the days in oem pistons due to it being thin between the first set of rings and the crown on higher boost levels.
@ Suspec... yes I’m seeing it from your perspective.. I bought this car used in horrible condition on its last leg and I rebuilt, replaced and restored as much as I could all except pulling the heads. I was told it had weisco Pistons but when I dropped the oil pan, it had eagle rods but I saw what looked like casting marks on the Pistons, unless they are those other hybrid type flexible Pistons. The guy also said he removed the air intake butterflies but bcs he lied about the Pistons I’m thinking he could have lied about other stuff too. He also said the ecu was a Jim Wolf ecu but I did not find any signs of mods to the ecu. On the fact that the spark plug has fine scratches all around the electrode instead of one hard impact leads me to HOPE it’s a butterfly screw bcs the car STILL runs but it’s under boost that the plug gets smushed again. Today I ran the engine and it’s all “seems ok” but at 2k rpm I hear a faint consistent high pitch rattle. The rattle is not present below or above 2k rpm. I have not dropped a bore scope in yet but when I zoomed in with me phone, there are impact markings on the face of the piston. I KNOW by extensive research that a stock piston is NOT going to hold 20 psi ESPECIALLY for 5-6 years but it did it! I was told the build was 3 yrs old when I bought the car and by the looks of it, trust me he been beating in it long time lol. Then I had it and drove it for 3.5 more years so the Pistons mayyyyy be something better then factory but they are not forged aluminum bcs they are not shiny and smooth, and they had cast marks underneath the Pistons when I dropped the oil pan unless there is something I don’t know... the valvetrain also got to be what he said bcs it held up all that time. But I hope it’s a butterfly screw so I can pull it out with a magnet.
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Dam Im sorry about that. Thats why its hard to trust almost anyone that has done work on it before. You probly want to find out quick what the issue is. If there is metal in there, you dont want it to embed into the cyl walls or any further permanent damage. You can pull the top half of the intake to look for a missing butterfly screw quick.
yes you are absolutely right about that!!!! I didn’t know JACK about turbo engines when I found the car but after 3-4 years working on it and doing extensive research and schooling, I know a hellllll of a lot more. Enough to build something simple like a b20/p75 and I understand tuning and read turbo maps and how to read egt & stoic values exc... I’m about to dive in now that I have time to work on the Nissan. I’m praying to be able to pull something out with a magnet and vaccum out debris and be done. I know it’s shady to not pull heads but it’s going to turn into a full head and block rebuild at that point bcs every thing else on that car is literally new. Fingers crossed 🤞
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