Bent rod - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

Samspeed · 01-25-2023, 11:24 PM

Can a tuning issue cause a bent connecting rod while hitting the rev limiter?
Car is a 2010 ss with lsa blower. 2.5” upper Btr stage 3 cam headers cat delete e60 with zl1 pump and bap. Happened on a 2nd gear hit from 3,000 rpm , tires unloaded around 5,500 rpm and it hit the limiter. Let out immediately and there was a rattle.
Checked rocker arms/ springs / push rods all looked excellent.
Pulled plugs and checked gaps. They were good.
Turned engine over by hand and it stopped
Pulled cylinder heads and all the valves look great
Head gaskets are in excellent condition as well.
The intercooler brick is double plated and in excellent condition.
Pulled the engine and discovered the number 1 connecting rod was bent causing the piston pin bosses to make contact with the crank counter weights.
Any thoughts on the matter is very appreciated!

JMI · 01-26-2023, 07:59 AM

Hi boost numbers with aggressive timing below max torque would cause that issue for sure.

Samspeed · 01-26-2023, 11:15 AM

It was only making 9psi though and the tuner said the timing ramp was soft.very confusing.

stevieturbo · 01-28-2023, 03:30 PM

Generally speaking no it should not.

But over the years on the likes of LS1Tech, there are a lot of reports of people with stock motors, stock ecu's....that have bent stock rods after incidents with the rev limiter.

I would imagine there is some sort of causation, because that alone should not cause harm, rev limiters done right should be safe.

Drifters bounce off the limiter all day on theirs for example and do not cause harm.

Or maybe it was just time for it to die

cc-rider · 01-28-2023, 05:01 PM

I took out my engine in a very similar fashion as your stating. Was doing a big burnout and hit second gear and lit the tires up to the rev limiter…felt a big shudder and dropped rpm. Ended up being that the guts of my (supposed) high flow cats let loose…and lodged in my x-pipe. This plugged my exhaust in an instant at high rpm and sent a huge back pressure pulse back into my engine and took out the bearing on the piston that was in the wrong spot at the wrong time. I didn’t bend a rod. But it wiped out the bearing. Knock, knock, knock…

If you have cats…check them.

stevieturbo · 01-29-2023, 04:05 AM

Quote:

Originally Posted by cc-rider

I took out my engine in a very similar fashion as your stating. Was doing a big burnout and hit second gear and lit the tires up to the rev limiter…felt a big shudder and dropped rpm. Ended up being that the guts of my (supposed) high flow cats let loose…and lodged in my x-pipe. This plugged my exhaust in an instant at high rpm and sent a huge back pressure pulse back into my engine and took out the bearing on the piston that was in the wrong spot at the wrong time. I didn’t bend a rod. But it wiped out the bearing. Knock, knock, knock…

If you have cats…check them.

That seems a very unlikely scenario.

Slowhawk · 02-03-2023, 07:22 AM

I've had a few customers bend a rod just banging 2nd gear on sticky tires. It can happen. Just rare.
Have had customers burn pistons from pushed back cats.

So,not really a new thing bending a rod. You found the weak link of your motor.

01-25-2023, 11:24 PM	#1
Samspeed Drives: 2010 2ss Join Date: Jan 2022 Location: Arizona Posts: 11	Bent rod Can a tuning issue cause a bent connecting rod while hitting the rev limiter? Car is a 2010 ss with lsa blower. 2.5” upper Btr stage 3 cam headers cat delete e60 with zl1 pump and bap. Happened on a 2nd gear hit from 3,000 rpm , tires unloaded around 5,500 rpm and it hit the limiter. Let out immediately and there was a rattle. Checked rocker arms/ springs / push rods all looked excellent. Pulled plugs and checked gaps. They were good. Turned engine over by hand and it stopped Pulled cylinder heads and all the valves look great Head gaskets are in excellent condition as well. The intercooler brick is double plated and in excellent condition. Pulled the engine and discovered the number 1 connecting rod was bent causing the piston pin bosses to make contact with the crank counter weights. Any thoughts on the matter is very appreciated!

01-26-2023, 07:59 AM	#2
JMI Drives: Red Jewel Camaro SS Join Date: Mar 2014 Location: East Coast Posts: 392	Hi boost numbers with aggressive timing below max torque would cause that issue for sure. __________________ BTR LSX388,AGP Twin Turbo.6L90,GM 9.9" Diff.Fore Innovations Level 4 fuel system.Great fuel economy !!!! 1xxx RWHP

01-28-2023, 05:01 PM	#5
cc-rider Drives: 2010 Camaro SS Join Date: Dec 2006 Location: MN Posts: 1,172	I took out my engine in a very similar fashion as your stating. Was doing a big burnout and hit second gear and lit the tires up to the rev limiter…felt a big shudder and dropped rpm. Ended up being that the guts of my (supposed) high flow cats let loose…and lodged in my x-pipe. This plugged my exhaust in an instant at high rpm and sent a huge back pressure pulse back into my engine and took out the bearing on the piston that was in the wrong spot at the wrong time. I didn’t bend a rod. But it wiped out the bearing. Knock, knock, knock… If you have cats…check them. Last edited by cc-rider; 01-28-2023 at 07:31 PM.

01-26-2023, 11:15 AM	#3
Samspeed Drives: 2010 2ss Join Date: Jan 2022 Location: Arizona Posts: 11	It was only making 9psi though and the tuner said the timing ramp was soft.very confusing.

01-28-2023, 03:30 PM	#4
stevieturbo Drives: it changes Join Date: Nov 2010 Location: Norn Iron Posts: 1,126	Generally speaking no it should not. But over the years on the likes of LS1Tech, there are a lot of reports of people with stock motors, stock ecu's....that have bent stock rods after incidents with the rev limiter. I would imagine there is some sort of causation, because that alone should not cause harm, rev limiters done right should be safe. Drifters bounce off the limiter all day on theirs for example and do not cause harm. Or maybe it was just time for it to die

02-03-2023, 07:22 AM	#7
Slowhawk Drives: 1999 Trans Am Join Date: Jul 2009 Location: Bridgewater,Ma Posts: 2,017	I've had a few customers bend a rod just banging 2nd gear on sticky tires. It can happen. Just rare. Have had customers burn pistons from pushed back cats. So,not really a new thing bending a rod. You found the weak link of your motor.