How does such a big engine produce so little power?

[Afromonk]

Having a browse on ebay for classic pickups when I come across this http://www.ebay.co.uk/itm/Chevrolet-454ss-Pickup-C... , now being a fan of the GMC syclone I look up the 454ss's power which rolls in at a measly 255bhp despite having a 7.4l V8

How does a engine of this size produce such little power? and is there anything you can do to increase it excluding forced induction?

[LarJammer]

Thats pretty good! cadillac coupe de ville, 6036cc, 140bhp!

[Fox-]

How much torque does the engine have? What do you think is most suitable for a truck - high revving high power or ample low down torque?

[IrnBruFreak]

Cause it's from the us ..

BHP = rev * torque...

You find the majority of us motors are built for low down torque and don't rev very high, hence the bhp figures are lower than euro take on large motors

[Mastodon2]

Another raging beast of a muscle car, the Mustang King Cobra from 1978, 5.0L V8 with 139bhp, a mighty 29bhp/L.

[Afromonk]

Ahh the whole revving thing kind of makes sense, just seems insane to have such a large lump with so little BHP.
Apparently it has 405lb-ft (546.8Nm) @ 2400 rpm which in fairness is quite a lot of low down power.

The Cadillac coupe de ville and the Mustang King cobra are both a disgrace

Out of curiosity is there a way to make the 454 perform without serious mods/and or forced induction?

[k-ink]

On the upside those unstressed engines will no doubt run for another hundred years with oil changes. Whether you want to to is another issue.

[Matt UK]

Fox- said:

How much torque does the engine have? What do you think is most suitable for a truck - high revving high power or ample low down torque?

Exactly. A Moto GP bike makes 240bhp, but it wouldn't tow 5 tonnes for 100,000 miles.

[brillomaster]

well assuming the flow of air is not restrictive, then simply advance the timing and hack the ecu to raise the rev limit - maybe stick a thinner head gasket in there to increase the compression ratio. admittedly all these things might make the engine fail prematurely, but while its working it should be making more power!

[9mm]

Poor breathing and fuelling as much as anything I expect although there are probably other issues around old materials, exhaust, friction surfaces and other stuff I don't understand. A book on tuning old engines will probably explain a lot of it. I seem to remember the phrase 'strangled by emissions equipment' back in the day concerning big US engines.

[GTiRichTea]

Reading up on that truck, the engine has a 7.9:1 compression, small ports and restrictive intake, which would explain why it makes so little power.

It also said it will do 0-60 mph 7.1 and Quarter mile 15.6 stock so not to shabby for a big old truck.

[carpetsoiler]

Cadillac Eldorado.

8.1 litre V8.

190bhp.

Emissions pipework had a lot to answer for in the '70s/'80s.

If you stepped back a few years, the Chevrolet El Camino 454 SS was putting out some pretty healthy figures from that same 454 lump- 375bhp+ was not unknown.

[XJ Flyer]

It's all about state of tune in the form of compression ratios,cylinder head design,valves/cam,and manifolding flow rates etc etc.

www.youtube.com/watch?v=fLCw2pi0O0I

Edited by XJ Flyer on Friday 6th December 00:56

Edited by XJ Flyer on Friday 6th December 01:01

[Baryonyx]

I can only imagine the looks on some of the faces of the blokes driving these Emissions Era cars for the first time. Expecting seven litres of big block V8 power and getting nothing back from it!

The US car market has always been a funny thing, mainly because it's so massive it could survive just by making cars for domestic sales. This led to an insular culture of taste and design. The Americans preferred big engines, even in spite of the 70's emission regulations. It's a strange place where piles of st like the AMC Pacer (penned by a cross-eyed idiot probably trying to copy European cars of the time) could have a 5.0L V8 and make 124hp.

[tali1]

Going back in time .... and sorry for thread kill .Thank you please.
1905 Panhard et Levassor 50 cv 21.1 litre/ 50 bhp =2.4 bhp/litre
For comparison
1886 Daimler 0.5 litre/1.1bhp = 2.4 bhp/litre

[anonymous-user]

The disco v8 had 180 bhp, i think that was 4 litres,it was all noise no go.

[benny 61]

Not just American cars my old 3tr Capri= 138 bhp
What has been the break through?

[slinky]

IrnBruFreak said:

Cause it's from the us ..

BHP = (rev * torque)/5252...

You find the majority of us motors are built for low down torque and don't rev very high, hence the bhp figures are lower than euro take on large motors

EFA

[98elise]

IrnBruFreak said:

Cause it's from the us ..

BHP = rev * torque...

You find the majority of us motors are built for low down torque and don't rev very high, hence the bhp figures are lower than euro take on large motors

Just to expand on this, quoted BHP is peak. Small high reving engines can produce high peak power but thats achieved through rev's, so al low revs the power is low. A large capacity engine low reving engine achieves is power through high torque, and normally across the rev range.

If both engines ran at peak all the time, they could do the same amount of work. As engines actually need to work across a range of revs, you want a big engine if you want to pull loads from standstill.

[The Wookie]

slinky said:

IrnBruFreak said:

Cause it's from the us ..

BHP = (rev * torque)/5252...

You find the majority of us motors are built for low down torque and don't rev very high, hence the bhp figures are lower than euro take on large motors

EFA

Technically the 5252 is only a scaling factor for units. In SI units (Nm, W and Rad/s) he's correct.

Gloyyyven!!