Technical What causes an engine to fail?

Everything.

 

This is true. I'm not particularly concerned about the specific engine in my car. I put most of it together myself (I assembled 1 engine out of 2 that I had), and the very tired shortblock needs rings and burns oil, but I don't push it hard anymore and as long as I keep oil in it it runs fine.

Last year, my Father In Law and I put together a fox-body mustang for the 24 Hours of Lemons race (yes, I realize this is OT but it speaks to the larger question). That car had a stock, low milage 302 SBF in it. After about 40 laps, despite good oil pressure and running at 185 degrees, the motor wiped itself out. Crank was totally scored, bearings were toast. Oil pressure obviously fell and that was it. In such a case, there was no single catastrophic failure like a thrown rod or dropped valve. It had good oil pressure. But the bearings got wiped out and the motor blew.

Is building a performance engine merely the task of assembling high quality opponents? I'd doubt it. That goes more to the question and point I'm trying to make. What else is entailed aside from just being super clean and following proper engine building procedures and specs?

 

Now that you mention it, yeah, you're right. Or sometimes just poor design, insufficient capacity or airflow. My old BBC Chevelle's always heated up in heavy traffic. My dd mini SUV was advertised as having 248 whopping horsepower and loads of torque from turbo-charged 4 banger. And it does run well. So I installed a trailer hitch and hitched it up to my little 17' 2100# wet travel trailer and set off to go camping, and the first hill I hit I was digging how that little engine just dug down and huffed right up the hill, very impressive! Until I noticed the temp gauge hitting max temp. Seems they gave the little thing plenty of power / torque for the job, but neglected to give it enough cooling capacity to dissipate the heat generated when you actually want to use that power for more than 20 seconds at a time getting own a freeway on-ramp. I have to back my foot out of the throttle as soon as the temp gauge starts to climb. Sometimes I'm just feathering the throttle pedal to make the top of the hill. I'm leaving 40 - 50% or more of the power on the table cause I can't use it or it'll over heat. Just a crappy design, they probably saved 50 bucks per car using a smaller radiator, not expecting anyone would actually want to tow with it. It's shame too, cause other than the heat it makes a great tow vehicle for the little trailer.

 

The life span of an engine is very different, but the quality of the parts and care taken when mounting them is paramount.
I bet you if you take a freshly build NASCAR spec engine but install a streetable cam, a small intake and carb that's blueprinted and set up for your power (and make sure it runs without a doubt not lean) install a RV sized Radiator for a small light car, never miss the shift point, run expensive oil (read good) and have the engine pre-heater (heating water and oil) and pre-pressurized oiling system.

So the only thing it will need to run forever is good maintenance.

But despite that I would also clame
that a stovebolt six is one of the best engines ever made, I would even make the bold statement that a 1950 barnfind with a six shooter pulled and given a big service some good and modern oils and some old gas (think receipt not old fuel turned warnish) new plugs and TLC will start run and take you to work like it was 1954 all over again. And that means an oil leak or two, some small water loss and the low MPG, but overshadowed by smiles per mile. And I even dare say, if one mind to take the rockers off and hit all the valves with a small hammer. Grease and refit rockers pure ATF/acetone down the plug holes over night before start up, that six shooter would run like it was 1954 again!
I like flatheads, but very few of them would do the same right out of the barn what a stovebolt would!


But I bet to this day that old school guys engines/cars last longer because they don't switch the engine on like a light switch, beat it when cold like sonny did with cher, and drive it at 4000 rpm on an engine designed to go 3000 or less.
And we check shit before use, only flight mechanic and hot rodder care about there own shit.
Apposed to pilots and ex-wifes!!!!

 

"Oil pressure obviously fell and that was it"
And the oil pressure failed for what reason ?

 

IDLING!gasoline in its liquid state washing down upper cylinders and removing lubricity cant be good.

 

Ive had two 230 chevy 6 engines fail for no reason. One the fiber gear in the cam shaft came apart. the other burnt a piston. it was a rebuilt jobber engine and I blamed It on sorry pistons. the most common engine failure for me was dropped valves. I like high RPM!

 

LOL I had a 300" ford one time that was recently remanned by a reputable local builder. It never really felt right but it motored around Ok in the old ford truck it was in. I decided to make a trip 80 miles one way mostly interstate. A about the 70 mile mark, kaboom then it ran like a scalded ape. But I knew that the kaboom was not a good thing, I pulled into a truck stop that was a little ways up the road where I knew the people and looked under the hood. Windowed the block. They said it could wait there until I returned with a two bar and truck and I hitch hiked home. When I got it home I tore into it, the broken rod was on the crank backward. Anything can happen and according to Murphy it will.

 

Top fuel cars rebuild the motor after just one run.

http://www.hotrod.com/how-to/engine/top-fuel-engine-rebuild/

 

SACRILEGE! (especially coming from a guy called volvobrynk, who should KNOW that the Volvo B16/18/20 is the best engine ever made!)

In all seriousness, the reason I love my Volvo engine is the same reason that engines function well in the real world and on the track: Start with an engine that was designed well, so that it can dissipate heat easily from moving components into the block, then into the coolant. Uuse quality components when building that well-designed engine, and most important, be meticulous about ensuring that every component in that engine fits well against its neighboring parts. Good fit along the crank components ensures high oil pressure, which reduces heat buildup. Good valve adjustment ensures that heat is dissipated around the valves. Good piston, ring and cylinder fit assures heat dissipation and reduced heat buildup, as well as good compression.

When you think about it, it's a truism to say that overheating causes engine failure. But that truism doesn't tell the whole story. There is always an underlying reason for the overheating. Sometimes, that reason is as simple as high mileage and associated wear, causing reduced oil pressure and then heat buildup until a rod bearing spins. But poor attention to detail during assembly will cause poor oil pressure, maybe poor heat dissipation, and result in early failures even with low miles on the engine.

 

Dry sump oil systems go a long way in curing oiling problems. Measuring rod bolt stretch instead of using a torque wrench is pretty standard. Cryogenic treated parts and performance coatings are standard fare for race engines.

As far as comparing race engines with production engines - production engines are measured by units/hr. Race engines, not so much. A top fuel engine that gets looked at every 10 seconds of running time can probably get by with a little less precision assembly than a endurance engine that has to perform for up to 24 hours.

 

In a word: Tolerance.
Spend the money to design and build an engine to a high level of tolerance and you'll find yourself in a Formula One laboratory (can't call it a "garage") with a 1.6 liter engine spinning at 20,000 rpm for hundreds of miles.

The problem is that it is impractical for mass manufacturers to build to such a high level of tolerance. The longer a car lasts, the less likely they'll sell you a new one.

 

All engine s designs have tolerances in mind, tight loose or in between they all have to be minded, an assembly line motor usually has a wider window to hit and at least nearly all American motors are not interference motors like an F-1 motor or some imports but they all seem to hang together as long as they are maintained properly.

 

I seen older cars that were checked every weekend and proper oil changes go 200K and the biggest contributor to wear was carburators or what we called carbonators , excess gas and carbon will cut a motor apart over time , these new cars with Fi control the oil washdown and excess carbon because of proper fueling plus it helps keep the gas/water vapor ( which makes acids and sludge ) under control too .

I have a engine ( 70 pont 455) here at the house that has 245K on it and very little wear and some carbon , it was taken care of by the little old man who owned it , the only reason I got it was the framerails and floor rotted out of the car , I felt I was cheating the guy when I gave him the $500 he was asking ( for the whole car) , the motor started up quietly and had good oil pressure and was clean ..

I recently bought a car cheap with only 63 K miles on it ( 2012 Impala LT ) for a flipper , it was a lease vehicle turn in , that the motor (3.6L ) was hammering , after draining the 1-2 quart of what was supposed to be oil , the original oil filter was on the motor (asy line paint marks on it ) and the drain plug was never touched , aparently the car never seen a oil change during the lease ( dealer could not find any record of it and they did them for free for the leases ) plus the brakes and tires were shot )
the company who leased it just put gas in it , washed it and drove it ( they detailed the car several times as we found the reciepts for that ) .My buddy at the dealer was going to sell it to a insurance parter ( the leasors insurance paid for the damage and the car wasn't worth fixing in there eyes ) , and he said with nowdays with leases this is not uncommon . people do not care or know how to take care of there cars anymore* . the motor was so badly damaged, bearings cooked like it was siezed as the saddles were discolored , I just replaced it with a good lo mile salvaged motor ( wreck) and sold it.

* In highschool when we took drivers ed they taught us how to change a tire and check oil and tires , when my step son took it in 2007 , they barely covered anything , and most importantly checking the things on a car , one student got a burnt out headlight warning ticket ....
.

 

plus some of the uber exotic materials they use in them little motors , just the price of a set of valves you could by a decent house with ... funny how they went from v-10s and 12s back to 6's and 8's

 

....after reading the above I see that the 1 reason that was not mentioned was ..." THE NUT BEHIND THE WHEEL "...

 

At least he isn't texting!

 

I always get a chuckle on break in procedure. The engine plant only checked to see if they started then sent them to the assembly plant where they are installed.When they ran the vehicle it was on an alignment rack for a few seconds then the drum was stopped and the car driven forward onto a moving belt. The fitter went around the vehicle with a big rubber hammer to make adjustments. At the end of the conveyor 4 drivers drove the cars into the parking lot and get a ride back. Next they were run long enough to load them on a truck or rail car to take them to a dealer.

 

The three "F's", assuming the auxiliary systems, i.e. cooling system are designed properly and in good working order.

Form, Fit, and Filth.

 

I THINK what Joe is looking for is partially answered in Beaners post # 38. Someone installed the rod backwards. I bet we all have done something of that nature. I think if we go back to Joes first post/question, if both engines received identical parts , two possibilities exist. One is answered by Beaner. The other , although all parts are identical, something is not. Details.

Ben

 

At the end of the day -what Squirrel said.I have been fixing peoples broken engines and teaching people to fix peoples broken engines for over 50 years.I have told thousands of students"if you dont beat it when its cold and change the oil with reasonable frequency it will likely run until you are sick of looking at it".

 

Big cam and big carb primary venturis = poor fuel atomization at low RPMs, which makes matters even worse. Too much rumpety rump = splish splash.

 

Thinned out oil or Sludge kills an engine,due to lack of maintenance, non detergent or crap oil . Sludge takes over the job of the oil filter and traps dirt and metal and then eats away bearings, ect. When the engine over heats if it hasn't deformed the block,the heat breaks all the sludge hanging on to the walls of the engine & dumps into the oil pan, clogging the oil pump screen. Its like throwing a grease caked cast iron frying pan on a hot fire and it will come clean.

 

And Just under 1000 revolutions under load

 

Poor study habits.

 

Yeah, when I worked in the equipment repair business, we'd fire a new or rebuilt engine up, check it for leaks, and if all was good we'd immediately put it to full load to bring it up to temp, check & record hi idle speed, lo idle, converter stall speed, full stall speed, turbo boost pressure, etc. Make any adjustments that needed to be made. Shut it off and re torque the heads, and put it back to work. There was no break-in procedure, no taking it easy, nothing. These were a lot bigger engines making a lot more power/torque than a hot rod, and costing several times more. $35k - $50k easy in parts and labor. There's dirt to move, trucks to load, etc, no time for taking it easy.

 

My old lady. She stands on the go pedal; causing one failure. The other she drowned (no s@#t submerged it)

 

Bad Engineering:
1. Selection of materials.
2. Cross Section of mechanical Parts.
3. Tolerances. (especially accounting for thermal loads).
4. Tribology (Friction, Lube, wear).
5. Manufacturing methods

All these are major factors in the service life of a high performance engine. Beyond these, as others mentioned is maintenance.

 

I agree with maintenance. I've taken quite a few DD's over 200K.

 

I knew one guy who scrapped cars for a living. If he found one that ran good enough, he'd take it for his wife to drive. He'd do what was called a no-parts tune up, just clean the plugs, points.. maybe splurge for a gas filter, swap newer wires off another junker. He told me that the secret was not to over heat them and keep up with the oil changes.

I drove a few junkyard dogs myself back in the day. Almost everything came off another junk car to keep them running. The 'yards would give stuff to us if they knew what we were up to.