Bent rod, engine ran fine

[justinh722]

I recently got a 96 GSX chasis and pulled the running 6 bolt motor out of my 95 GST. Up until I pulled the motor, the car was my daily driver. Aside from a idle problem, it ran just fine. Had the typical lifter tick but no major problems.

I planned to freshen up the motor before putting it in the GSX so I pulled the head. I noticed when number 1 and 4 were at TDC that the number 1 piston was like 1/4 inch lower. I pulled the pistons out and I find a bent rod. The bearings all looked to be in good shape yet. The cylinders were just fine. I did find a couple small chunks of metal in the pan but I couldn't figure out where they came from. They looked like piston material but could have been from a previous blown turbo.

Anyone know how or why this happened? I was running E85 with no knock counts. Who knows how long it's been bent though. Is it possible that it could have made the crank journal out of round? Would I be ok with some new bearings and a new rod? Thanks.

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[bastarddsm]

Man, if detonation did that I'd expect it to have the rod bearing pounded out of it, and the ringlands knocked off.

I bet it was hydrauliced. You might want to check that the crank isn't bent.

 

[ilco187]

Pre-detonation, hydrolocked.

i type slow

 

[justinh722]

Is it possible the previous owner of the 1990 GSX that this motor came out of had a head gasket go bad and only leaked coolant into the number 1 cylinder causing it to hydrolock? Maybe they replaced the HG without knowing. All I know, is that the motor ran good and pulled hard at 22 psi on a 16g with E85 and no knock.

 

[sciondan]

If the ring lands and bearings look good, id say it pulled cooant in and hydrolocked. Can't believe that ran good.

 

[4cedFed]

Wow iv never seen a rod bent like that and not knock, crazy.

I can't believe you ran 20+psi and it held up also. If it was still running good when you pulled it and the bearings/piston still look fine, just replace the rod, bearings and rings. If there are no marking on the crank you should be good.

An "out of round" crank would spin a bearing sooner then later, without a doubt at 20+psi.

 

[nfernotalon]

That's crazy just throw it back in and do 30psi ha

 

[tron2119]

That's crazy! You never know what you'll find sometimes.

 

[donniekak]

I've seen this in a few e85 cars now. Timing can be advanced past mbt, without any knock. When you do this the piston is still being forced up, against a fully burnt charge. Something has to give, usually a headgasket, but also a rod can bend.

I stopped using knock sensors on my e85 cars. I tune them by sparkplug reading, and logged times on the same road, through specific rpm ranges. When the times stop getting faster, i back off a couple degrees, and move on to the next set of cells.

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[justinh722]

I'm wondering if it was a prior HG failure but then again I won't ever know. I do know that I was lifting the head at 22 psi because I was pushing coolant. It would be fine at 17 psi but as soon as I hit 20+ it would fill the overflow tank. It coulda been my timing also. I think I was peaking at 22 around 7000 rpm on the E85.

I was running AFR's in the lower 12's upper 11's which I believe is fine for E85. The ring lands and bearings were fine. Although the bearings were kinda miss shaped and wouldn't seat in the rod or cap like normal. How the hell it didn't spin a bearing is beyond me.