I have a friend who claims that his dad did something to the family car several years back that caused a piston/rod to be ejected through the hood and onto the pavement while driving on the freeway. I have a hard time believing this is possible. Is it and what could cause such a dramatic event?
I am not a mechanic, but my guess would be that this is extremely unlikely.
I’ve broken rods before while going close to 100MPH and all I got was a dead engine with horrible noise, but the engine casing was not damaged.
If you approach this analytically, you will see if the engine somehow had the power to eject a rod through it’s own casing, through the head and onto the pavement it would not withstand its own operation. Since the situation does not allow for additional leverage or energy in the system than there is already, most of the damage during an engine blowout is going to be due to the torque and rods/pistons have no rotational momentum. Most likely is that a rod broke and possibly cracked the cylinder/headgasket and over the years the story got blown out of proportion.
I’ve heard this from more than one person. Maybe its more likely at a NASCAR event or the like.
Nope, it’s an embellishment of what happened.
It’s more likely a rod would be shot out the oil pan onto the ground than a piston head being forced through the head, manifold, fuel intake, hood, and anything else in the way. NASCAR has 700 H.P. engines turning upwards of 10,000 RPM’s and even when they blow up I have never seen an internal engine part laying on the track.
It’s less an urban legend than it is exaggeration of an expensive repair made out to gain a little ego-building.
It didn’t happen. Unless the engine was running on solid rocket fuel.
BTW, thanks for bringing up bitter memories. :mad:
I had a '69 Goat with a 400 that I threw a rod on doing 65 coming home from work. I made it the 20 miles from that point home, but I thought I’d go deaf or die of embarrassment from the noise it made.
$300 later (in 1991) I had a rebuilt 400 that still smoked the threadbare tires (I was poor) at 50 mph. Point is, a thrown rod didn’t do too much damage to the engine overall.
Good Lord I miss that car. :mad:
And being so pissed at my lack of current GTO-owning-ness, I meant to say a '68 Goat.
My day is totally shot now.
I have seen the engine/rad fan go through a hood (on a Nova SS). Never saw anything else from the engine compartment go through the hood.
I blew the single cylinder Kohler engine on my minibike when I was 13. It blew a hole in the side of the engine case and spalttered what was left of the hot oil on my leg.
That was the root cause, checking the oil wasn’t yet in my mechanical knowledge of internal combustion engines. The immediate cause was the stress of three kids on the mini bike going up a hill at full throttle.
Years later I broke three rods in a beater of a pick up truck. Nothing protruded from any point of the engine.
As a former race car driver, I have blown more engines than most folks. My attempt at racing a Chevy Vega resulted in 11 blown engines in half a season. None of the engine failures ever resulted in pistons flying through the hood but the lower parts in the engine compartment took a beating. One engine explosion was strong enough to cut the center link of the steering assembly in half. Another took a couple of brake lines with it. The best one was in a 67 Pontiac figure eight car. The 454 broke right in the front of the engine sending rods, pistons, crankshaft, and even the timing chain throughout the engine compartment. The frame of the car had bits of metal embedded in it and the heavy crossmember was riddled with holes. The timing chain ended up embedded in the grill of another race car.
I once threw a a rod in an '81 Pontiac Phoenix - the slightly gussied-up variant of the Chevy Citation.
The rod broke at the little end (piston, rather than crankshaft) as when I stopped, there was a fair sized hole in the block and the top end of the rod was peeking out with the piston sitting on top of it.
Other than the chunk of crankcase and whatever was left of the oil, nothing was actually ejected from the engine.
I’ve seen holes punched in cast iron blocks from rods that broke free of the crankshaft. I’ve never seen a piston ejected from an engine, though racer72’s experience indicates that it’s possible – but that’s an EXTREME and highly unusual case under extreme conditions. And note that even then nothing went through the hood.
In the great majority of engines, the cylinder heads are on top of the engine block, and it’s essentially impossible for a piston and/or rod to punch its way through the head. They could never reach the hood.
Some engines might be able to throw a rod upwards, but…the horizontally opposed engines I’m familiar with have intake manifolds and such on top of the block, and it’s hard to imagine a loose part getting past those. On a Chrysler slant-six engine, an errant rod might get aimed towards the hood, but I’m very skeptical that it would have enough energy to penetrate it after cracking through the block.
I don’t see how it would be possible for a piston to exit the engine unless the crankshaft fell out (a la racer72’s story) or the block somehow disintegrated. I can’t say it’s absolutely impossible for that to happen to a stock engine being driven at highway speed, but the odds against it are overwhelming.
Sounds to me like exaggeration, embellishment, and distortion of whatever actually did happen.
Thanks for this thread! I’ve thought about starting it myself a few times.
I’ve heard stories like the one in the OP many times since I was a kid. Never saw any corroborating evidence, always thought it was bunk.
I saw an engine that was on display in a rebuilding shop many years ago. It was a flat-head six cylinder that had been rebuilt by an apprentice. He had trouble starting it, removed a spark plug, poured the (entire!) contents of a six ounce can of ether into the cylinder, reinstalled the spark plug and engaged the starter. The rod burst through the block, the head fractured, and the piston more or less disappeared. IIRC, the crank shaft fractured, but I can’t be positive about that. Materials used in those days were not as strong as today’s but even so, nothing came through the hood.
Sure it can, at the dragstrip. I’ve never seen a street or race engine fire internal components out via the head but on the strip wierd things happen. If an engine is supposed to last seven seconds but only makes six and a half… I’ve seen a piston extruded out the hole where the intake valve used to be. I’ve seen a bearing on the crank seize and fling a rod through the block. I’ve seen many reciprocating parts get ejected through the oil pan - it’s just aluminum and not much of it either.
Look in the middle at the Keith Black engine…
On the street or track, you’re a lot more likely to see ancillaries and valvetrain components get jettisoned. My mother cut a tire on a pushrod from an old 302 Ford, and I’ve seen many a lifter while cycling down the side of the road.
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- As far as pistons sent flying, I have not heard of that happening to anyone IRL with a “normal” street-level car. I’ve seen cylinder heads cracked off from water getting in the intakes, and a few years ago a pal had an Audi Quattro that lost the timing belt, the piston hit the valves and broke the piston rod off at the top, and then the rest of the piston rod fell over sideways and smashed a two-inch hole out the side of the (5-cyl inline) engine.
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- With “Hot-rodded” cars, I think I’ve heard everything. When these kids get a small Japanese car (with a small engine) and then put twin-turbos and nitrous on it, they’re lucky if anything on the engine is useful after a blowup.
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Being a stock car racer, I guess I have to reply to this one too. I find it very unlikely that the story in the OP is true, but I don’t think I would make a blanket statement that it’s impossible. My worst “blown” engines have been from connecting rod failure. The exterior damage is usually a hole in the oil pan. On the inside, the broken rod generally breaks the block and the cam. I had one break up the cam and lifter area badly enough that it left lifters and a chunk of cam on the track. All of these went out the bottom though, not the top.
The first time I blew an engine, I had no real clue what was happening. I was letting off the gas to enter a corner. The next instant I heard a “jake brake” like sound and my car was swapping ends in front of 20 other cars. The engine had broke and seized. When it locked up, my back tires were on a trail of oil and water. I have never felt a car spin that fast before or since. I did get the clutch in and catch it after a 360. It didn’t matter. The trail of oil and water took 9 other cars with me including the one that rear ended my car. It was not a good night. Since then I’ve been able to recognize the signs quickly enough to not wreck so hard. knocks on wood
Between racing and auto repair I too have seen far more than my share of blown engines.
The two strangest that come to mind was a Trimuph Spitfire that would not start when it came it. Ran a compression test, and there was zero in #1. I pulled the head. When I looked down at the block there was no piston in #1! WTF? I pulled the engine and removed the pan, and found the rod, and many pieces of the piston in the bottom of the oil pan. The big end broke and the crank caught it, put about a half twist in in and about a 60 degree bend on its trip to the bottom of the oil pan.
That pales in comparison to the 454 I saw that came out of a motor home. One of the Chevy heavy line techs came over to my stall (I worked at a Chevy/Volvo dealership) and told me I had to come see what he had just taken apart. We walk over to his stall, where he shows me an oil pan full of broken bits, pieces of pistons, pieces of rods, pieces of camshafts! (think about where the cam lives in a 454) along with chuncks of cast iron, and lifters and such.
He then tells me not to miss the best part and shows me a small hole in the exact bottom of the oil pan. It is about 7/16" and has four pedals of metal peeled back from the inside. It looked like somebody fired a .38 relolver inside the engine and blew a hole in the pan. It turns out a pushrod got fired out the bottom of the pan. Oh yeah the transmission was destroyed when pieces of the camshaft went back into the bellhousing and did some serious damage to the torque converter and bellhousing.
But I have never seen a piston through the hood.
The engine out of B&I is on the stand in my garage right now (I build engines as a hobby). I busted the crank and 3 or 4 pistons beating the hell out of it. Nothing shot thru the hood. Broken cranks can take out the trans but nothing is likely to go out the top.
Although, my neighbor’s Porsche did blow a spark plug out of the head hard enough that it dented the hood.
Most of our racer boys who’ve checked in are far more experienced than I, but I did rack up some racing, and engine building, experience in past years. With a front-engined rear-wheel drive car, it seems to me that parts most likely to actually be ejected would first come from the front end of the engine (fan, belts, etc. - I did watch a harmonic balancer depart a Nova on the start line at Houston Drag Raceway in ~1968 and then proceed to crawl up my leg - it was very hot).
The next place I’d look for shrapnel borne of extreme stress to the system that actually departs the automobile might be the clutch assembly, and the first in line for risk of injury there is the driver. Next, I’d look to the drive train to lose some pieces.
Add me to those who vote that a piston through the hood is hard to imagine. I really can’t concieve of the physics that would deliver that scenario. The most extreme force a piston experiences in usual operation is in the downward direction, on the compression cycle. For it to be propelled through the cylinder head and related stuff would require a an explosion in the crankcase, and that would require some circumstances more unusual than just running it near redline.