how much loss of horsepower can be expected when going from gross to net. and what the heck does gross and net horespower mean? would i be better off getting a 67 396 or building up a more technologically advance small block? in terms of power, economy and reliablitly. any and all replies are appreciated

Thanks
dan

Think of it in terms of your pay check! Gross is what you earn and net is what you get to spend on car parts http://www.chevelles.com/forum/eek.gif ok pay bills with!!!

With HP gross is what the motor makes without all the power robbing stuff like alt, power steering, water pump, airconditioning and smog pump... Net is what you have with all the acc's hooked up, but before it gets sent to the rear wheels... I don't know a percentage off the top of my head...

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...Dennis
Topless '69 (http://home1.gte.net/ddunio/topless69)

As I remember it, Gross Hp is also known as Brake HP (bhp). That is the HP made at the flywheel. Net HP is the power put out at the tires after all the losses thru the trans, drive shaft and differential. The loss percentage is pretty sick, like 30 or 40%. It would be cheaper to get a mild 396 than to build a technologically advanced small block to make the same power and torque. Economy, small block is better as far as gas. Reliability, same. I'm biased, but if I had to do over again, I would still go Big Block! If you have the means, DO IT!

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Armando
So. Cal
66 Malibu,454,M22
64 El camino
57 Bel Air
95 Impala SS

thanks guys. but i thought that on the new LS1s people were talking about how they put around high 200s horsepower to the rearwheels but are rated at 305. so what is the 305 rating called? im confused not the smartest person.

Gross hp = Power without and accessories (water pump, power steering, ect.)

Net hp = power with accessories (not sure about A/C).

Rear wheel HP = power at the rear wheels, includes all power robbing accessories and the drive train.

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Pat Kelley
66 El Camino, daily driver
67 El Camino, STRIP/street
Pat's Page (CR Calculator, Utilites, car specs) (http://cochise.uia.net/pkelley/)

GROSS= pre 1972 ratings.
This was the hp at the engine WITHOUT water pump, alternator, (power robbing accessories) and WITHOUT drive train.

For a quick approxiamate conversion.

GROSS X .7 = NET.


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Creator of Team Chevelle's RADIO TECH (http://www.chevelles.com/radiotech) for original audio questions and answers

[This message has been edited by Coppertop (edited 11-08-2000).]

Gross horsepower and SAE net horsepower are BOTH measured at the flywheel. The ratings you see for modern cars are SAE Net, so they are rated at the flywheel, not the rear wheels.

It is correct that gross hp is rated without accessories or exhaust while SAE Net is with accessories.

I believe (my opinion) that, in general, SAE Net ratings are about 80% of gross.

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Dan Carr
dcarr@chevelles.com
Team Chevelle Gold Member #11, ACES #701
Author of the GMC Sprint, El Camino, and '68-'72 SS Authentication pages.
See my GM A-body fleet at:
www.rmi.net/~dcarr/cars/cars.HTM (http://www.rmi.net/~dcarr/cars/cars.HTM)

<BLOCKQUOTE>quote:</font><HR>Originally posted by needacar:
thanks guys. but i thought that on the new LS1s people were talking about how they put around high 200s horsepower to the rearwheels but are rated at 305. so what is the 305 rating called? im confused not the smartest person.<HR></BLOCKQUOTE>

A 2000 LS1 equipped SS is factory rated at 335hp net (all accessories hooked up!) from the dyno results I have seen this equates to 300-310 rwhp (rear wheel hores power).

Compare that to factory spec's of '60s cars you can see why these new muscle beasts are so quick. A '69 L-48 350/300hp was rated gross (before accessories were added). That 300hp turns to +-280 net then maybe +-260hp at the rear wheels....


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...Dennis
Topless '69 (http://home1.gte.net/ddunio/topless69)

thanks a lot for the info. it is appreciated and you have furthered my small knowledge of car.

DAN

Fine 69 I think that 300hp 350 would be about 250 net hp and about 190-200hp at the rear wheels.

As I understand it, gross was optimized and didn't even take exhaust manifolds into account. I also have seen formulas bandied about that seem to be different as to whether or not the engine is coverter equipped, ie. 70% pre coverter vs. 80% converter-equipped. I must check if I can find it. Also, hp at the rear wheels seems to me to outside the realm of this discussion, since both gross & net ratings were taken at the flywheel. Too bad a chassis dyno wasn't involved in the factory ratings. Ah, the mystery!