What are the main reasons that newer high performance engines can go much longer without a total rebuild than older engines we build? For example, the 485hp SRT challenger motor compared to a fresh built 500 hp aluminium headed 440 running less than 10.5:1 compression. . In most cases the 440 would need a rebuild or at least bearings and maube rings at a much shorter interval than the 392

Progress in assembly, oil formulation, fuel management, etc.

Back in the day, piston rings were a big one. Old cast rings versus moly rings, the difference is huge. Even in the late 318's and magnum engines, cylinder bore wear is night and day versus the old ones.

Also, fuel management. If you've ever cracked the head off a carbed engine compared to the same engine with port EFI, the pistons and valves on the fuel injected one are very clean. On the carbed one they are all junked and carboned up. All that raw fuel, running rich, poor fuel distribution, takes it's toll on engines.

1: Moly faced piston rings 2: Oil technology 3: Fuel management

4: AND this is probably the most important one, more so than the rings, harder bore sleeves. In 1981 it became federal law that cars had to pass emissions for 5 years/50000 miles. Old engines that were shot at 100K miles had significant bore wear at 50000 miles too (and were sometimes in need of a rebuild then). Bore wear leads to oil consumption and other nasty things that show up in emissions testing. So manufacturers had to make the bores hard enough to not be significantly worn at 50000 miles. A bore that is hard enough to not wear .001 at 50K miles doesn't wear much more at 100K miles, or 150K, and so fourth. Thats why we have engines with 300K miles that don't burn any oil and still make great cranking compression.

Overdrive transmissions are another reason that the engine last longer.

The cruising rpms on the highway are now 2k or less when they used to be 3-4k.
You've slowed the revs down by 50%.

As already stated with fuel injection keeping the a/f to where it needs to be there no more ring wash out and carbon build up.

EFI don't dump as much raw fuel on the cylinder walls because it atomizes better and is more precise. Fuel is a bad lubricant. The EFI on modern engines also has the ability to turn on a CEL and let average people know when there is an issue, with a carb the vast majority of people will never know when it gets a little out of whack.

Better oil control means they can run lower tension and thickness rings and that means less friction.

OD trannys keeping RPM down when not needed to be high.

Hypereutechtic pistons are used in most engines now and the alloy is more slippery as well as tighter fittin in the bore at cold starts thereby reducing blowby of carbon and other harmfull substances. It expands less than forged or even old school cast.

Machining precision, the machine tollerances are held to a lot tighter standard again reducing friction.

Oil is much better now than 50 years ago, there was such wide variations in oil back then that you could not mix different brands a lot of times.

Better ignition systems like coil on plug ensure more complete combustion.

Better material in the bearings block and rings and cranks...

More thought is put into getting the engine to warm up faster thereby lowering emmisions caused on cold starts, also the cars are heavy forcing the engine to warm up faster to a more efficent temp. Higher temp thermostats also make the fuel evaportate faster keeping it out of the oil. Hot parts also generate less friction.

There is more also and some of these things are easily added to old engines and some are not.

I've seen 727's go 100k+...

With zero fluid changes...


I've been in 225's with over 450k...

Seen 318's go 150k before I could lift the chain off the plastic cam gear...


Folks who did the maintenance, got the life...


Today???

Much improvement, no doubt...

Driven by 'warranty'...

It's the Japanese manufacturers fault AKA aside when the Japanese car invasion started back in the late 1960s they forced the American car makers to make better cars that lasted as long as the much cheaper Japanese cars and engines did the Datsuns and Toyota engines and bodies lasted way longer and used a lot less fuel than the Pinto and Vega cars did Of course progress and competion has a lot to do with any industries progress and development Mopar engines and drivetrains lasted a lot longer than the GM and Ford car lines did back then, Mopar started the Five and Fifty warrentee program in either 1963 or 1964, all the other cars had a 12000 mile or one year warrenttee back then, if my memory is correct. All of the other American car makers had to follow suit the next year to keep Mopar from getting all the new car and light truck sales that year
Edited, don't forget that the American car companys had large stakes, partial ownership, in a lot of foriegn car companys over seas, Mopar was in bed with Mitisbushi, Ford had Mazda, GM was in with Isuza in Japan and all of them where making cars and trucks in Europe and other country all over the world

unleaded gas is probably the biggest factor. overdrive transmissions drastically reduce rpm. better parts and better engineering.

Don't forget about manufacturing tolerances and processes.

Todays processes for machining are far more accurate than what was used "back in the day".

Ed

My opinion is fuel injection - but I am just some dude.

Interesting, whats the overall effect?

Lead sludge from blowby, also lead buildup on rings, combustion chambers, etc can gum up the works.

That's not to say all the old engines were used up at 100k, the IH sv series was known to go 300k between rebuilds. Those were carbd in the 60's. They were also industrial engines mmeant to chat away at 3 to4 thousand rpm all day everyday. High nickel blocks, forged cranks and generally heavy construction got them there.

lead wears an engine out. i don't think any metallics are good for them long term.

Not true about the lead additives wearing motors out, that is a bunch of horse pucky spouted by a lot of the enviormental haters If you go back to the engines made originally in this country for our cars and trucks before the lead additives where being used in the fuel the motors needed valve and ring jobs long before 30,000 to 50,000 miles The lead additives added to the gas stop the need for the valve jobs and also help increase the ring life along with better valve life The lead additives, Tetra Ethel (SP?) was a lubricant for the valve seats and cylinder walls that reduce metal to metal wear, it didn't increase the engine wear

lead and other metallics due wear engines out. i doubt that the intended introduction of "lead" in gas was a valve seat lubricate but more of an octane boost. before lead compression ratios were stuck in the 7:1-8:1 max. as compression ratios increased during the fifties more lead was dumped in the fuel. non-detergent oils were a big factor in engine failures prior to detergent oils which were developed around the same time as "ethyl" was introduced. but, believe what you want.

Without a doubt overdrive transmissions is the biggest factor.

EFI is better yes, but even they have to get run out on the highway to "blow the carbon out" every now and then.

Hmm. Had a 68 GTS 340, around 72-73 blew a head gasket with 125,000 miles on it. After pulling head, no ring grove at all, bores very smooth. I was expecting some wear but found none, lead gas and that bad oil, changed at 10-12 thousand mile intervals. Maybe I was on to something. Guy I sold it to turned it into a race car. 4.10 gears and headers, car ran low 12s for next two years. Lost track after that.

Here's what an engine designer says.

“The California Air Resources Board and the E.P.A. have been very focused on making sure that catalytic converters perform within 96 percent of their original capability at 100,000 miles,” said Jagadish Sorab, technical leader for engine design at Ford Motor. “Because of this, we needed to reduce the amount of oil being used by the engine to reduce the oil reaching the catalysts.

“Fifteen years ago, piston rings would show perhaps 50 microns of wear over the useful life of a vehicle,” Mr. Sorab said, referring to the engine part responsible for sealing combustion in the cylinder. “Today, it is less than 10 microns. As a benchmark, a human hair is 200 microns thick.

“Materials are much better,” Mr. Sorab continued. “We can use very durable, diamondlike carbon finishes to prevent wear. We have tested our newest breed of EcoBoost engines, in our F-150 pickup, for 250,000 miles. When we tear the engines down, we cannot see any evidence of wear.”

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“Competition is part of it,” said Peter Egan, a former auto mechanic and now editor at large of Road & Track magazine. “Japanese cars kind of upped everyone’s game a bit. With some exceptions, the engines would go a long time without burning oil or having other major problems.”

Hyundai and Kia, the South Korean carmakers, now include 100,000-mile/10-year warranties on their cars’ powertrains. If a relatively abusive driver can count on no major mechanical failures before 100,000 miles, a careful owner can — and does — expect his car to go much farther.

“My parents, with their ’56 Buick, used to have the wheel bearings repacked with grease before a long trip. Nobody does that anymore. The lubricants are better, the machining is better.”

from:
http://www.nytimes.com/2012/03/18/automobiles/as-cars-are-kept-longer-200000-is-new-100000.html?_r=0

Removal of lead, and reduction of sulfur from the fuel helped tremendously.

Finite element modeling of the engine structure and cooling system reduce assembly and operational distortion which reduces wear.

Ever look at how the head bolts are designed on a modern engine? they no longer are threaded to the top deck, but rather are long with counterbores to reduce bore and deck distortion.

Thermal modeling of pistons, valve bridges, and cooling systems is s.o.p now

Computer modeling capability wasn't available in the 50s and 60s. There was a lot of trial and error engineering back in the day.