Major
 

Ok how can you determine stock HP in an engine? For instance, my old engine had 164 hp in it, how much do you think is to the wheels? How can you dteremine that?

Dyno

chris

I always guess around a 20 hp loss through the transmission, but the only true way to know is a dyno test.

it's either dyno or some virtual engine programs like desktop dyno or stuff like that

You can figure anywhere from 15-30% drivetrian loss depending on everything from the crank to the wheels including clutch/converter, flywheel, driveshaft, tranny, etc. A good average is 20%.

*DING DING DING* V8killimports' got it. Generally speaking you can expect a 10%-15% loss through a manual transmission and 20%-25% through an automatic. So 20% is a good average number. It also depends slightly on the efficiency of your transmission. That percentage can also go up and down depending on your power level and parts. Take my last dyno...it read 657hp at the wheels. Using a loss of 20% (657 x 0.2) that means I'm loosing 131.4hp through my transmission and rear end and making 788.4hp at the engine. There's no way this is correct cuz my block would fly apart. But I've got a wide ratio gear set in the transmission and a really good converter so it lessens the loss probably a lot closer to that of a manual tranny. and cuts the actual hp loss in half. Still in danger of ripping my block apart...but not nearly as bad.

so my old engine had 164 horsepower in it, what do you think was to the wheels?

Roughly 131hp for an automatic...148hp or so for a manual. Remember...these are rough estimates at best. It can vary a fair amount even between two similarly equipped cars.