ok, I remember seeing an article in a recent car mag discussing this, anyone know which?

I'm hoping for 500 @ the wheels with the 396 LT4 (AFR 210s by agostino racing, comp solid roller custom but I'll say it's over .600 lift on both sides, 1-3/4" hookers, 58mm tb, 42# svo's)
this will be through a 4L60E w/ PI vigilante lock-up unit that stalled 2800-3000 behind the stock LT1, then to a "dead man walking" LCD 10-bolt (then maybe a 12bolt)

guesses, theories, opinions?
anyone tell me which mag?

thanks as always?

with 20% loss the motor will need to make around 625hp

I've always heard about 15% loss with a manual, or about 25% loss with an automatic. So like Quick said, about 625hp at the flywheel. The magazine your thinking of is Car Craft, they did a rwhp vs. engine hp article. I can't remember the month, but it was a couple of months ago. graemlins/thumbsup.gif

There is a real interesting thread in the Engines forum about torque vs horse power. Last I checked it was well into 2 pages long.

If you are using an automatic, keep in mind that you will be multiplying torque at lower driveline speeds. So while 20-25% HP loss is a reasonable rule of thumb, your at-the-wheel hp curve won't simply be 25% less than the at-the-crank hp curve. Just beware that it isn't quite as simple as multiplying the crank HP by (1-.25) to get driveline power. The rule of thumb is fairly good at estimating the difference in peak HP, but the peak will most likely shift and low speed torque / hp will increase due to the increased RPM of the motor through a stall converter.

why do "they" say that you lose a certain percent of power thru the driveline? doesn't a tranny use so much power, a rear axle use so much power, and the mass of things like the driveshaft use up so much power? i don't think it's ever as easy as saying "you will lose so-and-so percent of power produced at the flywheel thru the driveline". i do suppose the faster you accelerate things, the more power you will need to accelerate it even faster.
would you use different loss facotrs fo using synthetic oil vs. dyno oil in the tranny and rear end? how do you compensate for different tire diameters and weights, as well as driveshaft and even brake drum or rotor mass?
the only way to know for sure is to dyno your engine out of the car, then install it into the car and run it on a chassis dyno- then hope the engine and chassis dynos are both calibrated somewhat the same..
in the end, it only matters how fast your car is, not some power number that a machine tells you.

agreed derrick
wouldn't the apparant percentage of loss look smaller with a higher hp motor?

There are a lot of things that change from the usual engine dyno test to a chassis dyno test. Most engine dyno shops have their own headers, carbs, electric water pumps, etc. After you put this dynoed engine in your car with all the accessories installed and an inferior exhaust system, you'll be down some in power. Our tests have shown about a 15% loss with a manual tranny and 20% with an automatic. We dynoed a 450hp Vette that put 380+ to the rear wheels through an M21. We also did a 640hp Chevelle that put 527 to the rear wheels thru a TH400.