Old Engines are inefficicent at creating power/torque,WHY? 3

[mechanicat16]

Why do old engines produce such little power for their displacement, for example, the 1968 426(7.2L) hemi produced 425HP.The modern 6.1 L hemi produces about 425 HP, the same as the 7.2! Why is this?

 

[GregLocock]

Because for the last 40 years engineers haven't just been sitting on their bums playing on the internet.

Notice the rpm at which max power is developed - that's increased due to better materials, and perhaps better structural design.

The torque at max power has increased because you've got 4 valve heads, or better cams, or better porting, or better header tuning.

Every cylinder actually fires every time. That is a big help. Every cylinder has roughly the same mixture in it. That is a huge help. The cams actually open and close when the designer thought they should. That helps.

Also, no cold spots on the cylinder walls, able to run higher cc temps due to materials again.

But basically, 40 years of competition and hard work.

A cynic might ask why with hundreds of millions of dollars spent is the specific output of the new engine only 16% better than the old one?

That's a much funnier question.



Cheers

Greg Locock

I rarely exceed 1.79 x 10^12 furlongs per fortnight

 

[SomptingGuy]

and...

Better understanding of the mechanicals (rings, bearings, etc) relaxes self-imposed longevity limits.

- Steve

 

[patprimmer]

better oils and fuels also helps as does electronic controls which is what produces the results Greg states re reliable ignition and uniform mixture.

A big gain has been manufacturing technology to greatly improve precision and complexity at lower real cost.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[thruthefence]

Something else you might consider, are the insurance issues; back 'in the day' the rated horsepower contributed to your insurance payments. The hemis ,the tri power 440's ,the crossbolted Ford 427's, and the Chevy 427's of this era were all under rated.

can't vouch for this link, but it seems reasonable.

http://www.ultimatecarpage.com/foru...43-actual-horsepower-60s-70s-muscle-cars.html

 

[SomptingGuy]

Compare bike engines. In the early 90's 100 BHP was considered ample and almost became a legislated limit (in Europe). Nowadays bikes like the ZZR1400 are doubling that. Even the ZX10R is putting out 180+ BHP from a litre.

- Steve

 

[swall]

Thruthefence--I am having a hard time believing the explanation in the link. I was always of the opinion that the horsepower ratings at the time were SAE gross. If so, the ratings would have been determined by a standard test procedure and there would be no way to "derate" an engine for insurance purposes, as that would conflict with the test results.

 

[BrianPetersen]

swall, there are all sorts of ways to play games with this, both then and now. That was an era of mechanical (points and breaker) ignition timing, mechanical carburetors, etc. Think "production tolerances". To give but one example, the ignition timing on the factory spec sheet, and the ignition timing that the engine shipped with, and the ignition timing that actually gave peak power, can be three different things. Sometimes you can game the test procedure, too. If the official test procedure calls for stopping the test at the manufacturer's specified maximum RPM (remember, that was an era before rev limiters), then you just specify an artificially low maximum RPM.

Modern engines are built to tighter tolerances and have fewer adjustments ... but games can still be played.

The difference between SAE gross "back in the day" and modern SAE net corrected figures makes the difference in specific output from then to now bigger than it first appears.

Improvements in other areas besides peak power are more impressive. Fuel consumption, for one. Back then, anything with 200+ horsepower got 7 mpg. The reduction in emissions is spectacular by comparison. And then there's durability, driveability, cold starting, etc.

As others have noted, engineers have been doing something in the past 40 years.

 

[evelrod]

Agreed that time does not stand still, ESPECIALLY for the engineering professions. However, it's the huge advancements in electronics that are responsible for much of the gains. That and manufacturing technology advancements, also in part because of modern computers and electronics.

A blanket statement that old engines make so little power...
Take a peek at some of the early 1920's Indy engines. DOHC, 4 valve, duplex supercharge/turbocharged, methanol fueled, etc. As for machining complexity...try the Jumo 211, DB 601 or, RR PV-12 Merlin. I've seen the internals of all three and they do not lack for any deficiencies in machining. Especially the Jumo...it is like a Swiss watch.

Your right, Greg. WHY aren't we further along the curve?

Rod

 

[dgallup]

WHY aren't we further along the curve? Because they limited themselves to a long stroke OHV pushrod port injected configuration. For a more modern layout, look at the 4.5 l V8 in the new 458 Italia. 570 hp naturally aspirated, 127 hp/l vs 70 for the hemi.

 

[mechanicat16]

Thanks guys, I'm buying a 1968 GTO, my first car. It has the stock 400 engine with the TH400 tranny, it produces about 350hp, is there any way to get more horsepower from it? I know i could buy new parts, but i just mean modifications i could make to the existing engine.

 

[evelrod]

No problem, mechanicat16...It's a simple formula. Just remember---Horsepower is directly proportional to $$$ spent. More $$$, more HP !

As to the OP, the 426 Hemi Superbird that I had the chance to see run up on a chassis dyno made well in excess of 425hp AT THE WHEELS! You need to brush up on the "politics of the era". Big brother had a BIG influence on published numbers!

Since you specifically ask for advice---From someone who has BTDT---Stick fairly close to the stock setup for your GTO. The closer to absolutely stock you can make it will pay dividends further down the line. You can get by with a mild hydraulic cam setup, maybe a set of headers (keep the original stuff)...dual exhaust with the stock exhaust manifolds works just as well on the street, though...and, a good Pertronics or similar electronic ignition. That's about it. You will have more power than you can ever use on the street.

"Why aren't we further along the curve"? Wow, DG. Perhaps I was being TOO subtle!

Rod

 

[SomptingGuy]

Then there's materials. There haven't been too many new ideas in the last 40+ years, just ideas that are now practical.

- Steve

 

[dgallup]

Rod - I always thought horsepower was proportional to dollars cubed.

And I agree about keeping the 68 Goat close to stock & keep all original parts if mods are made. Look at the Barrett Jackson auctions, it either has to be a really wild custom or totally original restoration to get top dollar. Typical backyard hot rodder mods will kill value.

 

[RossABQ]

Pontiac made some seriously good cylinder heads and other go-fast parts back then, under their Super Duty label. These are still around, VERY pricey, but in general will not detract from resale value (to a collector) the way an Edelbrock or Weiand part would. (Save all your original parts!) A friend with a '66 Goat just picked up a desirable set of 455 heads, and had them freshened by a Pontiac specialist. He has over $2500 into them, and they won't do much good without the related parts (manifold, cam, etc).

Do you really need more power anyway?!

 

[lawayosh]

I believe back in the 60's that the High Priest of Horsepower, Reverend Mr. (Keith) Black stated that "How fast you go is directly proportional to how much money you spend!" As we could not afford one of his drag motors we were not quite as fast as others less fiscally challenged.

Back then, the cost of insurance would go up with the HP rating. So, many were labeled with lower than actual net and way under the gross HP ratings. Part of it was to make it more affordable for the typical young, barely insurable (remember assigned risk?), wanna go fast car buyer. If I recollect, a magic number was 300 HP, which my '69 Z/28 Camaro, with a 290 HP sticker on the air cleaner, just got under. With a '71 Z/28 I gave my insurance guy the 275 net rating instead of the 330 gross and was able to avoid the factory hot rod insurance penalty again.

Mechanicat, it has been said already and I will say it again, if it is totally stock, leave it that way or make only reversible modifications, keeping the original bits.

Yosh

 

[dicer]

In the old days gas was cheap, they didn't have to worry about being effcient. And when you say old engines, you need to be more specific, because the automotive world of engines has taken years to catch up to what the aviation world was. Huge difference there too, automotive engines usually only run at 20% of capacity when driving down the road, aircraft is more like 80% or so, kinda like any continuous industrial application like a pump or generator, the HP usage is constant. The only time you need HP in the automotive world is accelerating and passing.
I also agree about those big auto engines of the past being under rated for insurance reasons.
Another reason they would not rate them or make them output more HP is most all manufactures then had a performance parts division, and to sell hot rod parts you don't want to make the stock engine that great, else your performance parts department would not be a needed entity.
And its taken the after market to figure out how to make such things as high flow cylinder heads, that has added greatly to the increase of HP in the auto engines of today.

 

[YvesLLewelyn]

To get back to the original question: Cars from the 1960's were carburetter types - a carby must always have some pressure drop across it to draw the fuel in - lowering the VE. (and generally quite a bit of air flow restriction in the carb to make the cars more "driveable"). Modern electronic fuel injection systems don't have this problem. Also most manufacturers have taken advantage of the port injection etc. to use tuned length intake runners which add to the power. The FI use alone probably adds 15% or so to the torque/power.
Two engine types that make an interesting comparision are the small-block Chevys and the modern LS1-type engines. Both are pushrod, both 2-valve but the LS engines make far more power more easily than the old engines.

 

[lawayosh]

Something that you have to consider is how much influence the bean counters had on what made it to the showroom. Making more HP out of the same size envelope takes better materials along with more engineering and manufacturing sophistication. There were people at the Big Three that knew how to make plenty of power with smaller packages. How to get it made at a required price point was probably an insurmountable challenge. Now, with fuel economy as a major influnce on design, smaller, lighter engines that can make more power with less fuel are a necessity. Of course, this ups the cost. Oh boy, to remember that a '57 Chevy with a fuel injected 283 was about $2000 new, and now??

Yosh

 

[thruthefence]

That's $15,269.54 in today's dollars. Not a bad deal. I'd buy one, but order it without the F.I.

or you can get a bespoke version:

http://www.autoblog.com/2006/08/22/57-chevy-for-sale-again-50-years-later/