mngreg

Did a search but couldn't anything on this but...

What do you think an LS3 would be rated at using the old gross hp rating system from the 60's and early 70's?

Just curious...

Gearhead Jim

One of the magazines did an article several years ago, and concluded you couldn't simply add "x" percent to the new rating to find the old rating.

Having said that, I'll open the bidding at about 500 hp gross.

davanz

About 540 - 570 gross rating. The net ratings are usually 70 - 80 percent of gross but vary from car to car depending on intake, exhaust systems and tune.

This is why the old muscle car hp specs look impressive, but their peerformance in literal stock, showroom condition falls far short of our modern machines. And yes i was there. I well remember when a car that could do 0-60 in less than 10 seconds was considered really fast.

AORoads

it could be 500 or even 500+ would not surprise me. the numbers were so all over the map.

I remember someone saying that if you ever experienced 400 rear wheel horsepower, it'd practically snap your neck. well, I guess that one was wrong.....not that a stock LS3 is RWHP, but the 500 crank hp cars are more than that.

Vette5.5

Probably not even worth the time to speculate, as RWHP HP is really the only thing that matter's. I recall reading some article's on older muscle car's, and 325 RWHP was a rarity on anything stock out of the factory. Should give some kind of indication.

not08crmanymore

L88.
ZL-1. TERRITORY, I would imagine.

GSRANDY

I have always used a 1.15 multiplier, i.e. 436HP X 1.15 = 501.4HP.

Regards,

GSRANDY

C6LSx

Can someone explaine to me the difference?

From what I understand; "Net Horsepower" as with our 436 BHP LS3 engine is calculated with the LS3 engine on a dedicated engine dyno with all of its accessories attached including the NPP mufflers.

If my assumption on calculating "Net Horsepower" in 2010 is in fact correct; can someone please explain how the "Gross Horsepower" was calculated on a 1967 C2 equipped with a 427 ci engine producing 435 BHP?

TIA -

AirBusPilot

http://ateupwithmotor.com/automotive...orsepower.html

davanz

In the 60's horspower era it wasn't unusual to determine advertised horsepower in this manner :

Put the engine on a dyno wth no exhaust system , (or maybe high quality headers), no air filter, no alternater, power steering or fan belts. In other words, have the crankshaft turning nothing but the dyno. Pump coolant through it from an external source, have the room temperature at optimum, and set the cam and ignition timing for best "test stand", not "street "performance, and some impressive numbers could result. These numbers could then be used in sales brochures, ads, etc.

Put that same engine under a hot hood, turning power steering pump, allternater, water pump, and smog pump in some instances. Put on a street legal exhaust system and an air intake system to filter air quietly, tune it for acceptable street driving and the horsepower would fall substantialy.

The net hp ratings supposedly account for all these parasitic losses so that a more true rating is given.

johnodrake

I would say 525 SAE Gross for the LS3 and 532 for the LS3 with the NPP.

I base this on the 71 - 72 LT1 - same motor 330 SAE Gross in 71 and 270 SAE Net in 72.

C6LSx

Thanks for the link.

While 15-20% is the general guideline, is there a firm percentage number of parasitic drive train loss for the following LS3 C6 platforms?:

1. C6 A6

2. C6 M6

BTW: My understanding is that the Nissan GT-R AWD has the lowest recorded percentage of drivetrain loss at a recorded 7%.

Gearhead Jim

Even today, I sometimes suspect that GM numbers are written by the advertising department, not the engineering department.

Vette5.5

I enjoyed that article too. Really show's how some of those old gross HP rating's could just be a number pulled from the air. Also recall some of the GM 10HP/LB limit, where some of the Firebird's came from the factory with a throttle stop. A pair of plier's when you got home, and another 30HP. Also the reverse a few year's ago, when some of the asian car's were overated and some american car's under. Wonder if this will ever end.