Dyno comparisons

[JPhil]

I'm going to start a dyno comparison thread of my car. I just got the new 383 back yesterday. We ran it on the engine dyno. Soon as I get it installed I'll take it back and put it on the chassis dyno and post those numbers. Then next year when I change out the TH400 to the TKO600, I'll post those numbers. Enjoy.

Here's what we ran yesterday:

SBC Chevy, 4.030 bore
Scat 3.75" cast crank
10.4:1 HE pistons
Lunati single pattern hydraulic roller cam: 274* adv, 218* @ .050", LSA 112*, .492" lift
Comp 1.6 full roller rockers, for .520" lift
AFR 180 heads with 71cc chambers
Weiand #8000 3/4" rise dual plane manifold
OEM Quadrajet (Lars tuned)
MSD distributor with 6A box. Initial 13*, total 37*, mechanical advance only
1 5/8" full length headers into 2 1/2" pipes with X-pipe & Magnaflows




Dialed in run with full exhaust, no air cleaner- 433 lb/ft & 391 HP:



Run with full exhaust and air cleaner- 437 lb/ft & 396 HP:



Open headers- 434 lb/ft & 400 HP:




Interesting, huh?

Stay tuned.....

 

[JPhil]

OK, here's my chassis dyno readout:

OEM TH400
2000 stall torque converter
4L80 HD Intermediate drum
34 tooth sprag
Red Alto clutches
Colleen steels
2.75/1.57 gearset
Trans-Go kit

3.36 rear end
27" diameter tires
3600 lbs actual weight




Fully 25% drivetrain loss!!!! Yipes!!

 

[JPhil]

And here's a comparison chassis dyno from the 350" motor before this build:

All same specs including trans except--

350" CID, 4.030" bore x 3.50" stroke
9.75:1 compression
Comp hyd. flat tappet cam, adv. dur. 268*/280*, .050" dur. 224*/231*, LSA 110*, lift .477"/.480"
with 1.6 rockers= .507"/.510" lift
Vacuum spark advance connected





The numbers tell me this wasn't such a bad motor after all, but the butt-dyno feel really let me down. This motor felt like a pooch. I also had a worn out advance bushing in the distributor.

 

[JPhil]

Here's the dyno readout for my TKO600. It sucks half the power that the TH400 did, only 12% compared to 25%. I did not expect that great a difference, but the numbers prove it. I gained 60 lb/ft of torque and almost 50 horsepower to the wheels.




Here, I'll reprint the TH400 dyno sheet for quick comparison:

 

[69427]

I don't have any experience with chassis dynos. How do they account for differences in vehicle weight during these runs?

 

[phantomjock]

John -
I'm liking your new found torque - A LOT! Hope my 383 (10:1) does well. It will be a bit before I'm ready to Dyno. It will be a chassi dyno too.
Cheers - Jim

 

[JPhil]

I don't have any experience with chassis dynos. How do they account for differences in vehicle weight during these runs?

I don't really know. I don't remember what all he asked me as entered my info into his computer last year and now he just clicks up my 'account'. I doubt it's that important since a dyno run is not a timed run like a quarter mile, it's just a measure of power to the wheels. It may or may not be a correction entry like air pressure, ambient temperature, tire size, etc. If it were a correction entry I would think it would have to be total vehicle weight and then axle weight also.
Somebody else will have to answer.

 

[69427]

I don't have any experience with chassis dynos. How do they account for differences in vehicle weight during these runs?

I don't really know. I don't remember what all he asked me as entered my info into his computer last year and now he just clicks up my 'account'. I doubt it's that important since a dyno run is not a timed run like a quarter mile, it's just a measure of power to the wheels. It may or may not be a correction entry like air pressure, ambient temperature, tire size, etc. If it were a correction entry I would think it would have to be total vehicle weight and then axle weight also.
Somebody else will have to answer.

I appreciate your honest answer.

The reason why I'm curious is that different weight cars will accelerate at different rates given the same engine power (obviously), and this differing acceleration rate will affect the speed at which the rotating engine and drivetrain parts spin up and "store up energy/eat up power". It just seems like the choice of gearing and inertial drum weight can have a noticeable affect on the power readings.

Just trying to understand how chassis dynos relate to the real world.