Dyno numbers/ good,bad,explain......

[philbay]

No one seems to want to help explain this. 70 chevelle, 454 30 over,4 speed 355 rear, 27"tire... 781s ovals. In shop just finishing new guides, seals, valves, and had them cleaned up with portwork. I had a blue smoke problem,thus the headwork. Motor has a mild hydr. cam with hypo pistons. Here are the results. pull1 332hp-414tq, 311hp-415tq, 334hp-428tq.. I noticed on all three pulls, the rpms never went to 4000 .. So my questions,,, can it be that the car does not pull anymore than that. I certainly never thought the motor fell flat and I went to 5000 rpms all the time.. Do you think these numbers,dynojet rear wheel numbers,are low.. and what would you estimate my ET might be..

[nitrorocket]

The power could have been falling of real hard. Maybe they shut it down at 4000 because of this.

[camcojb]

Actually the numbers aren't off in my opinion for a mild big block combo. A friend dynoed his 427 combo at about 340-350 rwhp as I remember with aftermarket heads, cam, etc. He also hoped it would be higher.

Do you have the dyno sheets to post up?


Jody

[3kidsnotime]

Seems like normal mild 454 numbers to me, The car was probably laying over after 4k so no more reason to pull it.

[Old Man]

It's a big block the RPM's look just about right to me and I would say the power is right inline with what a mild BBC should make. I take it those are RWHP numbers, if so you have to take into account parasitic HP loss for the drive train. Manual transmissions lose less HP's than do an automatic on the dyno and you still have to look at what it's losing to the rear end. A 10-20% RWHP loss thru the drivetrain seems to be fairly common.

[Z-man]

Originally Posted by nitrorocket

The power could have been falling of real hard. Maybe they shut it down at 4000 because of this.

I think this is what's happening. On the dynos I've seen, the computer takes over and tries to accelerate the engine at a certain pre-set rate. When the engine can't do this anymore, the power peak has passed so the pull stops.

[chevymitchell]

A lot of people dyno thier cars and look at the horsepower reading and get disappointed. I did when I saw the sheets. Dyno computers horsepower readings are just a product of an equation. A dyno actually reads torque, which is what you drive, and enters that informatoin into a formula and puts out a horsepower reading. For a mild 454 with the setup you have the torque seems right. I would guess you would be running low 13's with you setup. Your horsepower reading are always going to be lower than torque before 5252 rpm, no matter what your dynoing. I wouldn't be disappointed in your numbers, they seem just right.

[rocketman]

Are these rwhp,if so it's in the 400hp range at the flywheel which for a mild 454 isn't all that bad,hp is made on the topend so the heads,cam and intake all effect that,so if it's running out of air a 4k the topend is hurting you