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5.3 sbe pulled head found something I wasn't expecting
I got this motor from a guy who bought it from a "wrecked running truck" aren't they all... Made two hits with it first pull on 93 octane no intercooler no meth 11.9-12.0 the whole pull on afr. 15* of timing. Second pull it blew the waste gate line off the intake and went to 15psi stayed at 12.0 afr timing for some reason went up to 16* according to the log but tune was calling for 12 in that map range but that's beside the point. It pushed out the head gaskets and emptied the block of water in about 400 ft.
Tore it down to do head studs and mls gaskets and found this piston that's missing some of the top of the # 7 piston. Looks to me like long term detonation but wanted a second opinion.
I agree it was leaner than I wanted it we had just started tuning it. If it was the tune I'm 100% okay with the learning lesson. It just looked old to me and was trying to decide if I did it or it was a previous issue.
It would be very hard to convince me that you did that kind of damage to one single cylinder with two runs. You would be harder pressed to convince me that it had anything to do with the tune at the time if all the other cylinders looked great. If every other cylinder looks good- then it sounds like a pre-existing condition, and if you follow that logic, you must inspect your fuel injectors flow rates, for that cylinder potentially had a poor-flowing injector is one of the few ways such damage would occur to a single cylinder.
another theory is oil got in there somehow, that would cause the damage you see to a single cylinder also. Do you see a trail-line of oil running from the pcv valve through the intake runner to that cylinder by any chance?
Every intake runner had oil CAKED in it but nothing I noticed in particular to this cylinder. And it has brand new simens Deka injectors with literally 20 mins idle and 2 pulls on them. Br7ef plugs FYI . Like I said it was a junkyard motor so it could have had an injector issue prior to this
Pull it and get a side view. Looks like the ring butted and it pulled the top of the piston off to me. It's very common. Go super light on timing with pump gas IMO. 10* tops over 15lbs until you can get the fuel dialed in and a good plug reading so you know what is going on in the cyl. I had a few pistons like that in my first "ran great when pulled" 5.3.
It's really a good idea when doing your wide open throttle pulls do take the first one to 4000 rpm, then check out your readings. After that, go up in increments of 500 rpm. A lot of engines could of been saved by following this routine. Bob
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I have to say that sounds super aggressive of a tune to me. No meth no IC, 2 pulls can do that under those conditions. 15 degrees and 15psi with an IC is pushing it especially at 12:1
It would be very hard to convince me that you did that kind of damage to one single cylinder with two runs. You would be harder pressed to convince me that it had anything to do with the tune at the time if all the other cylinders looked great. If every other cylinder looks good- then it sounds like a pre-existing condition, and if you follow that logic, you must inspect your fuel injectors flow rates, for that cylinder potentially had a poor-flowing injector is one of the few ways such damage would occur to a single cylinder.
another theory is oil got in there somehow, that would cause the damage you see to a single cylinder also. Do you see a trail-line of oil running from the pcv valve through the intake runner to that cylinder by any chance?
That sort of damage could be done in 2-3 seconds...even less.
There is no way a stock engine in a stock vehicle would suffer damage like that
At 6000rpm, that's still 100 turns per second, 50 firing events..plenty of time to cause serious damage through improper tuning.
True in general theory. But with these ls motors with the stock style intake we all know #7 goes first. I have melted 2 number 7 pistons in my day. Rest were fine. Nothing wrong with injector or anything cylinder specific.
11-09-2015, 04:38 PM
5.3 sbe pulled head found something I wasn't expecting 
