"Blown Engine"

[KSMike]

Has anyone ever blown up a SOHC from overreving it? I have I was playing around with my 2001 the other day in 4wd low and I got the rpm up around 6500 and the engine let go. I was in drive, letting it run through the gears at WOT and it didnt seem like the rev limiter kicked in, at least not before two rods came out the bottom. I've already got another engine in it, but just curious if any one else had done this.

 

[jimbo74]

i have never heard of anyone actually breaking an engine due to over reving other than a real drag car..

i kinda did it in my 85 yota, but that 4cyl doesnt like doing 50 mph in first gear for over a mile....

 

[Chew_12]

That is quite impressive

 

[Billy177]

i know 6500 is the max allowable rpm some people have their chips set to shift at 6500. did you have rod knock before that or something

 

[V8Exploder]

why would you do that...... Talk about an expensive "little" mistake

 

[KSMike]

Oh heck, why would I do it?, I just had a couple of grand I wanted to throw out the window no, there wasn't and rod knock ahead of time, at least not for more than a couple of miliseconds...... I really expected the rev limiter to kick in, because I know it does normally around 6,000. The engines must be pretty durable, if held to a reasonable (<6,0000) rpm, because they are quite plentiful at the salvage yards.

 

[GimPin]

did it to a civic once ... rev'ed an integra LS motor to 8000+ several times and it finaly decided it didnt like it anymore and threw a rod through the block

 

[bipolarbob]

We did it to a dodge dart once. It reved for about 3 mins, and then flames came out of the bottom and then it started missing, knocking and nuked. It took a long time. A few seconds and it blew? You must have had a bad rod bolt or something. Did you do an autopsy to determine cause of death?

 

[KSMike]

I did a very quick "autopsy" and my best guess would be a broken rod bolt. I found two rods had the bolts broken on them. One rod was twisted in half and the pistons were almost vaporized. That was the first time I had seen the inside of a 4.0 and I was suprised by two things, how sturdy the rods were but how puny the rod bolts were. Im used to seeing 3/8 and 7/16 rod bolts in race engines, but these bolts were tiny. No evidence of a spun bearing. It was only at WOT for about 3 seconds when it let go with no warning, other than going beyond 6500 on the tach. Im not sure if anything was savable in the engine. It wiped out both sides of the block and the oil pan and even did some minor damage on the outside of the engine. Im sure the heads were probably trashed also, but i didnt look at them.

 

[bipolarbob]

It's allways the rod bolts

 

[hermitrl]

Imagine how much torque load that engine and drivetrain was under--especially in low range. Looks like the engine was just the weakest point.

 

[Shinibents]

This message would've been a little more unnerving for me if I'd have seen it last week when my Nav was stuck in 4low. I'm even happier that it's fixed after reading this.

 

[bipolarbob]

Hey I didn't see you were in low. I put mine in low all the time and then the shifter to "L" and the rev limiter kicks in instantly. It takes less than half a second to rev fully out.