What do these spark plugs tell you?
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Joined: Mar 2006
Posts: 140
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From: Portland, Or
Car: 90 Chev Suburban 4x4, 5.3L, th400
Engine: 2002 5.3 Vortec swapped in.
Transmission: Stock th400
Axle/Gears: 10blt front/ 14bltSF rear 3.73 gears.
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From: Hou. TX
Car: 86 TA, 91 B4C
Engine: 5.3, 4.8
Transmission: 4L80 4000, T56
Axle/Gears: 4.30 M12, 23.42 10 bolt
It looks like 4 of 8 have rich condition and your rings are weak, the other four look old.
Thread Starter
Member

Joined: Mar 2006
Posts: 140
Likes: 0
From: Portland, Or
Car: 90 Chev Suburban 4x4, 5.3L, th400
Engine: 2002 5.3 Vortec swapped in.
Transmission: Stock th400
Axle/Gears: 10blt front/ 14bltSF rear 3.73 gears.
i have about 50 miles on the motor and plugs
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From: Orland Park, IL
Car: 1984 Z28
Engine: SLOW carbed ls
Transmission: TH400 with brake, 8" PTC converter
Axle/Gears: moser 9" 4.11
i'm guessing oil passed the rings then, or valve seals/guides. they all look alright other than that, not entirely as lean as it could be though.
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From: Calgary, AB, Canada
Car: 1982 Trans-Am
Engine: 355 w/ ported 416s
Transmission: T10, hurst shifter
Axle/Gears: 10 bolt, true-trac, 3.73
Those are the plugs you put in the car to fire up the new motor? I wouldn't even bother trying to read those, breaking in the motor will give all sorts of weird plugs as things seat. Unless you see something drastic ( I don't ) I wouldn't lose sleep over it. Drive the ***** off it and seat the rings etc.
I'd just read them after a few hundred miles
I'd just read them after a few hundred miles
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