Technical What causes an engine to fail?

I drive to work about an hour and a half in each direction, so I have a lot of time to think. Today's musing was, "What specifically causes an engine to fail?" Or more specifically, what is the difference between an engine that can perform at high performance, for extended periods of time, and just a regular-ass, stock running engine? Obviously, the quality of components plays a significant role. It goes without saying that a forged steel crank is stronger than a cast crank. But that can't be it, and I don't accept that if the people on the assembly line were slapping together engines in mass with race components that they'd be strong enough to handle the rigors of competition. In other words, if Yates and some random GM worker were both given the components of a NASCAR Chevy R07 engine, when assembled, would they both equally be able to run 10,000 RPM for 500 miles? My guess is no. So I'd like to hear from some people who are specialists. What is it that specifically that causes engines to break?

 

In real life? Lack of maintenance...

 

A heavy right foot has broken many

 

push rod exiting the side of the block

 

Mechanic failure

 

Over heating is mostly #1,but the list is big.

 

You have too long of a commute and too much time to think.

 

Poor or no maintenance, dirty oil, lack of oil, overheating, dirty fluids.
Pushing it beyond maximum limits for an extended period of time, again = overheating, oil issues, are possible....

 

I totally agree, but this is only the beginning of the answer. Specifically, what about hard driving causes engine failure. Inability to manage heat and breakdown of oil viscosity? If yes, then could a palliative measure be to use a high volume pump in conjunction with a increased capacity oil pan?

 

Cold engine starts are the worst thing you can do to any engine. It won't cause the motor to fail right away, just wear out quicker then fail.

 

As far as why a race engine will last for 500 angry miles and a stocker won't, it's got to do with the development work that is done before the race engine is built, money (lots of it), attention to detail.

I'm guessing there isn't a single OEM over the counter part in a Nascar engine.

Most street engine failures that I've seen are caused by abuse and neglect (oil changes etc. But some are just worn out.

 

Dirty oil = water jet cutter, cutting thru all that iron.

 

I agree w/Dana re: overheating. Or lube issues.
Then, if you look at higher output loads, my first guess would be wear-over time.
Rare, at least in the SBC world, have I seen fatigue fails. Any neglect like not cleaning out a block prior to assy, or re-torquing heads, rocker quality, stud pinning reqd. for higher valve spring strengths, can bring the Big Ooopps.

 

True, considering that Ford and Toyota haven't built a pushrod engine in over 20 years.

 

Yep that's it right there. ^^^ more than any other reason.

An assembly line engine should actually be more consistent than a one off engine. Look at it this way, the fella that checks the crank does it day in and day out with the same numbers and the same tool everyday, the fella that torques the heads is a head torque guy and he torques them day in and day out everyday. All the engines are identical and every component comes down the line identical day in and day out everyday.

Now a one off engine is just that one off. No consistency there at all and lots of room for a mistake. usually the same guy tat torques the crank is the guy that ground it and he is the same guy that measures the cylinder clearance and torques the heads. In the world of engine assembly he would be considered a jack of all trades as opposed to the assembly line guy who does one thing and hopefully does it well.

 

And using straight 30, 40, or 50 weight makes wear at start-up worse. Or even 20w-50. That's because lower viscosity oil, like 5w-30 or 10w-40, flows better on cold start-ups and gets pumped to bearings and valve train sooner. Only after warm-up do you need 30 or 40 weight. I'm not sure when you'd ever need straight 50 or 20w-50 except for intentionally loose clearances or to compensate for worn bearings.

 

That's a great point. The assembly line engine is actually strong. Amazing how the average car engine now can last 200,000 with just basic maintenance.

 

Apples to oranges.

Heat+stress=metal fatigue-->failure

 

True enough, and the thinner oil also allows less parasitic loss and has less stress on the oil pump drive.

I have a 454 in my pickup truck that has 184K on the clock, and I run 20w50 in that, which has helped keep oil pressure at a more appropriate level with the wider bearing space

 

Talking pre roller cams, break-in procerure (or lack of) plays a big part.

 

Something on the inside that wants to get out does it for me.

 

Dana nailed it. Overheating is the #1 cause of engine failure. #2 would be contamination, which pretty much is because of poor maintenance as Squirrel posted. Dirt is the #1 contaminant, but coolant contamination of the engine oil has killed many engines. So has fuel dilution, though it's not as common, but it happens (more common on diesel engines because of the lower volatility). Over extended oil drain intervals. Incorrect oil or poor quality oil, or even running low on oil, these are all maintenance issues. But there are myriad causes for engine failure, from improper assembly procedures (improper clearances, improper torqueing of fasteners - too tight or too loose, incorrect parts, etc) to exceeding the performance limits, i.e. over revving, or lugging; to metal fatigue (every part has a life span of x number of cycles it will withstand before failing, eventually every part will fail). Some forged or cast parts fail prematurely because of impurities in the metal, what are called "inclusions". A list of every possible cause of failure would be a long list.

 

Look at it this way in the later '60s both FoMoCo and GM had a 302 that was a general screamer. Both engines were assembly line motors, both ran best above 4K and preferred to be running in the 6-7K range and both motors were good for 100,000 miles with general maintenance. I have actually run one of each from the Lake of the Ozarks to Dodge City about 450 miles give or take, ran them hard, played while I was there and ran them back. Went to work on Monday.

Take any motor no matter who screws it together and flinch at maintenance and it will fail. Run it out of oil or without water, or gas fouled oil and it is doomed from the time that you got it.

 

And overheating is almost always caused by lack of maintenance....

 

Neglect when it comes to maintenance,not checking or changing the oiling on a regular basis, overheating because the radiator is low. HRP

 

Overheating is probably the number one reason for engine failure.
lack of proper periodic maintenance is probably number two with dirty oil, dirty filters and actually running out of oil.

Lack of preventive maintenance is right there too. Who's daily commuter rig with 5 years and over 100K has had all it's belts and hoses changed lately? We go over our hot rods with a fine tooth comb before hitting the road most of the time but that get you to work in traffic rig often still has the original belts and hoses after it's ten years old.

It's funny in a way but the lowest mileage rig in my yard right now is a 92 Dodge Dakota with 95K actual miles on it that has a broken timing belt. I picked it up for pocket change to get the front suspension. The thing even has tow bar brackets on it that show that many of those miles were behind a motorhome as a dingy. Again the result of preventive maintenance killed the engine.

 

I can personally guarantee that running with no oil with do it every time. And that adding 5 quarts at the next gas station is a waste of money. It's amazing the noises they make as they slow down right before they grenade.

 

57Joe....This is a case where knowledge can be a curse. Knowledge/worry used to wear me out on rides in my old cars...I'd be waiting for shit to break. Rarely happened luckily. Assuming you maintain your car and watch your gauges...say Fuck it. Since it seems I've gotten a little older lately I don't get wound up as often with things I can't control. Get AAA and if it breaks you get it home and fix it....

 

I drove semi truck. And Maintience plays a big part. however the nut behind the wheel plays a big part. After about a million miles Metal fatuge sets in. A rubber ball will only bounce a certain number of times. My 66 GMC is receiving its Bi Annual oil & filter change today It probably has some where between 4 and 5 thousand miles on the oil & filter. I never mess with the spark plugs since it has electronic ign.I have seen engines ruined by too few oil & filter changes. I have never seen one ruined by two frequent oil changes. I installed a rochester two bbl carb. The holley since I didn't open it up the secondairy the gas turned to varnish.

 

FRICTION

Less = Good
More = Bad