pepperdad

i have an 85' iroc-z with a 305 tpi motor and a 700-R4 trans. i was recently looking through readers rides and kept reading about people with 305 tpi engines saying they make about 190rwhp stock. i did research on my 85's rwhp (stock) and i found it to be 215rwhp (stock). why is it that other people with the same engine as me claim to have different numbers? what am i missing?

Morley

THEY are missing the cam that came in the 85 TPI engine. The 85 TPI engines got the "good" cam, the years that followed the 305 TPI's got the "peanut" cam.

Z28DJP1987

NO 305 TPI came with 215 RWHP I will say again no STOCK 305
TPI has that RWHP. Any numbers you read are at the FLYWHEEL
and not at the rear wheels.

jfreeman74

I have the same car and the numbers that are listed on this website at https://www.thirdgen.org/newdesign/tech/techdb.shtml
are pretty accurate with my car. According to the site our cars have 215 HP and 275 TQ. I believe these numbers are at the crank and not at the wheels which would leave you at about 180RWHP and 230 RWTQ. If you look at my sig. you can see my dyno results stock and with mods.

Morley

No, not at the wheels, GM didn't rate their cars in RWHP, just at the crank (flywheel)

pepperdad

so the car makes 215 hp at the flywheel, but by the time it gets to the rear wheels, it's only 180 hp. where does the hp from the flywheel get lost along the way? at the torque convertor in the trans?


p.s. thanks for the link.

Z28DJP1987

About 20% of this power loss is divetrain related. Tranny, dr.shaft, rear axle and etc.

jfreeman74

Your drivetrain loss will be anywhere from 15-20%. It varies depending on if you have an auto or manual tranny. Someone correct me if I am wrong but I believe you have a higher loss with a automatic tranny than with manual.