While estimating horsepower is a good excersice you will never know just how much you are ACTUALLY putting out until you dyno it.
Repost from a much earlier thread:
My Dyno Experience
Well last week I decided to put my Cobra on a dyno and just see all those four-hundred and yadda yadda horses I've been bragging about. Just like talking to a new date, we tend to embellish things.
Now my engine certainly has the potential for power: 351W bored +40, TRW forged pistons, Edlebrock performer plus cam and timing setup, 58cc AFR alum heads with Harland Sharpe Roller Rockers, Edelbrock Performer intake, 650 Speed Demon, etc. and running 93-94 octane.
I was really disappointed when I saw my rear wheel hp at 267 and torque at 330. I really thought that I would be more powerful than that. Hey, with a 2400 lb car that will still propel it down the highway at tremendous velocity but, still, I should be getting more…right? Even allowing for 18% power loss through the drivetrain that is still only 315 hp at the crank.
Well I faxed the dyno sheet down to the Demon tech guys. They were very helpful and I made the following changes:
1) Replace the progressive linkage to one-to-one
2) Raise the throttle cable on the carb to the big 1/2" hole to allow for full stroke of the linkage and better leverage.
3) Rejet down 2#'s from 70/78 to 68/76
4) Replace my 1/2" open spacer with a 1" 4 hole spacer.
Well I did all this, at very little cost, and took another run on the dyno yesterday.
I made three runs and all were about the same: 291 hp at the wheels and 365 lbs of torque!! What an improvement!! This is almost 350 hp at the crank and there is still room for improvement.
I just faxed the results down to Demon for more suggestions. Now running 66/74 with 315 rwhp and 392lbs of torque.
Anyway, I guess the point is that we all tend to talk up our cars but you never really know what you have, or where you need to tweek, until you get it on a dyno. I certainly had the potential but was not tuned properly.
You would be kidding yourself if you try to estimate what you are running. You can only estimate potential and not actual. You could sit around all day and say "well I should be running 375hp in that puppy!" It is a feel good experience only.
Then you find when you dyno it you are actually running 300! Not a feel good experience.
Best to get to a dyno and get that engine tweeked and running at its peak potential otherwise you will never know.
I guess some people just go around telling everyone they've got 400hp and that satisfies everyone but don't you really want to know what you have under that hood? Don't you want that engine maxed? I do.