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Started into my winter tear down (low oil pressure at idle) Got the heads off and saw this on my rear cyl 7 (8 has a similar mark except on the top) I JUST read a thread about this maybe 3-4 days ago, cant find it again. Something about these rear cyl run leaner and causes this and maybe worn rings? 30k miles on the engine so i would doubt it, but im finding some weird things.... first owner might have been a monster
I think blow-by is the incorrect term... but what causes this? is it something to correct while i have it torn down? Also does this seem like a extreme amount of carbon build up for 30k? I did have a good amount of oil in the intake, car also sat for 3 months, then made a 9 hour drive and immediately had the engine pulled if that is relevant at all.
That clean area could be a sign of coolant getting in there. How did the gasket look? Ever have issues with coolant running low? You may have never noticed as just a small amount seaping through would "wash" that area of the piston. I'm sure a new gasket and proper torquing NEW HEAD BOLTS will fix it...don't re-use the stock head bolts...they are torque-to-yield and should never be re-used.
Is your engine stock? Cylinder 7 is notorious for going lean. I've seen many pictures over the years with cracked pistons in that very spot (mostly with LS7s).
That clean area could be a sign of coolant getting in there. How did the gasket look? Ever have issues with coolant running low? You may have never noticed as just a small amount seaping through would "wash" that area of the piston. I'm sure a new gasket and proper torquing NEW HEAD BOLTS will fix it...don't re-use the stock head bolts...they are torque-to-yield and should never be re-used.
Yes bone stock.... you say this now and i just remembered the drivers side was MUCH MUCH harder to get off. My little air compressor worked its heart out.... i dont see any signs of it but maybe this head was off? gasket on both sides was glued together all the same, kinda a pita.
Yes bone stock.... you say this now and i just remembered the drivers side was MUCH MUCH harder to get off. My little air compressor worked its heart out.... i dont see any signs of it but maybe this head was off? gasket on both sides was glued together all the same, kinda a pita.
Did you put a straight edge on the heads and block to check they're flat? I'm still thinking it was a head gasket leak.
Did you put a straight edge on the heads and block to check they're flat? I'm still thinking it was a head gasket leak.
yep, 3 ft straight edge visually contacts the whole face well. No indication on the gasket. Whatever thread iirc read it was something about oil coming up from below but yea, head gasket leak makes alot more sense to me.
12-12-2023, 02:07 AM
Piston "blow-by"
