Seems strange the lower oil control rings look like they butted as well. Thats not common, I wonder if they just got trashed when the others let loose. I hope so, I just re-gapped the top 2. You really think power alone bent the rod? Haven't others made quite bit more power without bending the rods?

 

people with gen4 rods and pistons have made more than this yes

gen3s are known to get bendy at 650+rwhp

might be my particular tuning style but i break lower lands alot!

i did on my civic when i learned what i could get away with timing wise on 25psi

 

After everything's been so mashed up like that, you can't use what they look like on the pistons as much of a guide for anything, you'd have to check the oil ring scrapers inside the bore, but that's not of much use either as the oil rings run so cool there's very little expansion in use and as long as they aren't butted or overlapping they're good enough.

But the damage shown is classic 'exceeded the power limits' damage, and not detonation. The bent rods and ring lands happened as the piston was already on the way down the bore, which can only happen from too much power. It's all showing signs of compressive failure - ring butting from detonation (i.e.: heat) will stick at the top of travel, and pull the piston tops off.

 

Thats amazing!! I'm still collecting parts for ls project and I bought two motors (they were cheap lol) The first one I'm just going to toss in until it pops, but the second I plan on opening the rings up and putting some better rod bolts in!

 

the rod bolts are not a failure point

dont waste your money

 

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OMFG, that one rod was tweaked and you were still pounding on it LOL! How many of the existing rods "appear" to be twisted or bent?

 

all of them were bent, that was just the most obvious

didnt get my parts today

 

Were you still reving it to 6800+ ? The 2003 5.3 in "Truckin" magazine made 1300 hp without bending a rod. Isn't the gen4 stuff the LS2 2005 and up? Or did they start earlier? I know they were keeping the RPMS to 6k or so. Seems like most of the big power stocker motors do as well. Just wondering if the extra RPM did the bending.

I don't see how you can tell at what point the damage occurred? Inertial loads are the nasty ones, not power loads. They go up with the square of the rpm in­crease. So RPM puts quite a bit more strain on the con rods that the boost will. You will always have the most stress at TDC and BDC. I'd think most likely the rods bent at one of those points with the excessive RPM, not from power alone. Why would you think it bent on the power stroke? Like you said if the rings butting were the cause of the rods bending I think it would have pulled the piston apart and shown in the piston bores. It has for me in the past anyway. Usually takes out the rod and piston completely.

 

they were making power up to 7k i believe.
i think that pushing an engine dyno and actually pushing a car are two different loads on a motor.

it could be that the octane is so high the motor wont detonate and pre-ignition is bending the rods, but i doubt that.

honestly im not an expert i just swing a big hammer

 

Good stuff!!

 

You may be thinking of the 4.8 "bigbang" deal? The 5.3 was cutoff at 6300 rpm according to the article. QUite a few others have made well over 650whp without bending the rods as well. If one were trying to squeeze the most power from a stocker, lowering the rpm and upping the boost would be less stressful on the rods...to a point of course. I'm glad your doing all this testing for us! Soon enough I'll be out there blowing these things up too.

 

What about when the headgasket failed? Coolant in the bores+ attempting to compress= something's got to give, even if just slightly. Then the continued hammering aggravated the situation??

 

I thought you bought good pistons and rods.

 

well i bought gen4 stuff for this 5.3

you might be thinking of my 6.0 stuff i bought, i bought weisco pistons and Compstar rods for that.

ballin'

 

what did ya have to spend on the gen 4 pistons and rods

 

it was like 80 shipped

 

Have seen quite a few rods like this in diesel engines that have had heavy doses of either...... so I agree with herder on the compressive load bending the rod. I always thought rpm failure were more evident with wrist pin, rod bolt, or rod breakage near the ends of the rod. And x3 on the butted rings pulling head of piston off.... saw a few times working on diesel pulling stuff.

 

Where did you score that deal?

 

ebay
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