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#1 |
![]() Join Date: Jun 2022
Location: Alpharetta
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No SES light, but the car definitely wasn't running optimally in the low RPM range. Pulled the plugs on the driver's side. Cylinder 5 (assuming driver's side front to rear is 1/3/5/7) was coated in oil on the threads...no oil pooled in the socket.
Most of you probably know already, but the LS based engines use the same size plug as the LT5, so I swapped out that plug. Gap was significantly smaller than the others. Didn't appear to be mechanically gapped, so I don't think there was any piston contact. Need to check the passenger plugs, and will use the rest of my NGKs to do a halfway tune up. I won't replace wires or coils for now.PXL_20220705_235729766.jpgIPC_2022-07-05.20.02.42.2530.jpg Sent from my Pixel 3 using ZR-1 Net Registry mobile app |
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#2 |
![]() Join Date: Jun 2005
Location: CenCoast California
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That plug is badly oil fouled. I'm not sure about what I saw in the second image. By chance is that the piston top shot through a bore scope?
In any event, you may have a problem with a valve seal or a broken ring.
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Hib Halverson Technical Writer former owner 95 VIN 0140 current owner 19 VIN 1878 |
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#3 |
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#4 |
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#5 |
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Car runs smooth as glass now. Interesting how things run when all cylinders are firing.
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#6 |
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Wouldn't a compression test reveal if there is a broken ring? Why not try that. --Bob
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2016 Long Beach Red Z06 #10281 "POPS Z" 1995 Polo Green #409 "WARP TEN"--Haibeck 350/510 package, 4.10s, Hurst, Stock Exhaust with QTP Cutouts --Sold but still running strong 1993 Quasar Blue #161 "HIL KING" --Sold but still running strong, now with more than 120,000 miles 1967 Marlboro Maroon/Saddle Corvette Coupe 300 hp/4-spd --Sold a long time ago ZR-1 Net Registry Founding Member #95 NCM Lifetime Member Favorite Quote--Attributed to Mickey Thompson: "Too Much Horsepower is Almost Enough" |
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#7 | |
Join Date: May 2007
Location: Chicagoland, IL
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Had a similar situation with my old block. Compression tested fine even though compression ring was cracked in 4 places from detonation due to a bad injector. However, I was getting oil smoke under acceleration. Depending on which cylinder, ie 1/3 or 2/4, could be injector housing gasket allowing oil seepage from one of the oil windage ports.
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#8 | |
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Location: Alpharetta
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I can pull the plenum at a later time and get the injectors cleaned and flow tested to ensure proper operation. Slap some new o rings and see what happens. But if I had to do some engine upgrades.... Sent from my Pixel 3 using ZR-1 Net Registry mobile app |
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#9 | |
Join Date: May 2007
Location: Chicagoland, IL
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[SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX |
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#10 | |
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Location: Alpharetta
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Would it be best to ship to a company that knows the LT5, or would any reputable injector refurb place be up to the task? |
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