Well, a buddy mentioned a place here in Northern Virginia who had a dynojet and today I made it over there in my 73 454 with headers and 99k miles on the car (not sure how many miles on the engine since I haven't tracked down when it had been replaced). It's had aluminum heads put on, a Holley carb (not stock obviously), side pipes & headers, 200RPM B&M torque converter, 3.08 rear.

During the first run, they stopped in 3rd gear and said they needed to disable the vacuum kick-down function and they clamped off a vacuum line (I haven't taken a pic of the particular line they clamped).


Here's a rather disappointing result:



And here's a link to a video where I could hardly keep from crapping myself as I heard the RPMs climb!
http://youtu.be/10Et7jnaOTU

Few questions:

1) Why is there only 182HP? Obviously not something anyone here can answer without more data, but I'm guessing this should be producing more and want to know where to start looking.
2) Is the smoke at the end "normal"?
3) Is the HP and Torque delta "normal"?
4) Why is it necessary to disable the kick-down for WOT?

 

Might get a little on decel dont worry about it. Or youre blowing carbon out.
Looks shaky up top wonder if youre floating valvesprings
They werent powerhouses stock torque wasnt bad though.

Dont feel bad a "built up" sbc I did many yrs ago put down the same thing couldnt believe it. LOL Old clayton dyno
Probably an honest low 14.high 13 sec car.

how does it feel on the street?

 

You know - it feels a LOT more ballsy than my 190HP BMW. It's hella quicker off the line and certainly burns out the tires on command. Never done that in the Bimmer.

Also, I was just looking at the stock specs of the 73 with a 454, and the lowest HP they produced at the engine was 275. Is it possible I'm losing almost 100 horses to the tranny? I thought they only lose 25% or so?

Is it possible the dyno run is giving bad numbers?

 

Turbo 400? You can lose a lot to the rear wheels yes
Stall converter even more
Dynos are humbling:forget #s.
There are dyno queens out there that couldnt run a good # at the track if they tried.

Take it to the track see what it does.
COuld be old valvesprings timing etc.

Just have fun

 

yes, it's easy to lose 100 hp through the drivetrain.... normal numbers is 30% losses (give or take 5%). Turbo 400s are pigs on hp because there's so much mass inside.... of course, they also don't break, and ask the late Lingenfelter said "torque sells cars".... which is why your BMW is a slug comparatively speaking.

Still, your motor is somewhere near 310 hp at the crank - not bad for a smogger motor... need more everything to make that a stomper

Smoke - yes, dynos are terrible to motors - especially if the tech is "driving".... I lost a piston because of a tech's stupidity on my first dyno session, never again will I let them drive.

Yes, you need to disable the kickdown at WOT, otherwise it'll change gears and the results will be useless.

and here's what an inexperienced efi tech can do an acquaintances' 320 Buick... the owner was a nice guy - told the tuner that the 320 'had weak cylinder walls' - steam locomotives have thinner walls... more likely, the fuel flow wasn't balanced across the injectors and they put too much fuel into #1
http://www.youtube.com/watch?feature...&v=Nnn6-QPoN3A

 

I have heard the same about the turbo 400's taking tremendous power from the equation. I am pretty surprised myself that a smog 454 only puts that amount of power to the rear wheels. Take a look below:

http://forums.corvetteforum.com/c3-t...-the-dyno.html

At my 78 L-82 4 speed-not an automatic-with all original components-motor never been apart. I run a Holley 650 4175 spreadbore Q-jet replacement, 2.5 inch duals, McJacks shorty headers, zero pollution control of any sort, and comp cams 1.5 roller tipped rockers. My engine also runs about 50 degrees cooler than when it was smog latent and totally stock. Best dyno pull was 233 RWHP and 269 TQ-with the stock 882 smog heads. I did blow some smoke on Decel from the passenger side cylinder bank-just a hair. I did also just did a compression check on all the cylinders since this past October on the dyno, the engine was pushing a lot of whitish smoke through the pass side Valve cover breather. The engine has been pushing light smoke through the breather for years but decided to find the cause after the dyno runs. #6 cylinder is "weak"-90 PSI versus 160-165 PSI on all the others.

My point is that even with a weak cylinder, the L-82 with smog heads did 233 RWHP but the 73 454's really did not have much more Net HP than the 73 L-82 (which is the same engine as my 78 L-82). That tranny could be a 50 RWHP difference than the 4 speed, I suppose.

 

You may be running out of carb and cam on the top end.

 

consider a cam swap if the engine has the original valve train.

 

Did you verify that your carb is actually giving you full throttle? If it is, you either have weak valvesprings or the cam is not opening those valves very far. I say this because your power peak is at a very low RPM even for a very mild street cam. I'd start by checking the throttle cable to make sure it's opening the carb all the way.

 

I concur. The description of your engine and the power peak at around 3700 rpm don't add up.

When checking for full throttle opening, don't just check it at the carb linkage, have a helper press the gas pedal all the way down, and visually observe how far the throttle blades are opening. Lars has said He has seen cars gain 25 horsepower just by removing the floormat!


Scott

 

As Les mentioned, your HP rpm peak is way low. Chevy advertised the horsepower rpm at 4400. (for a stock 73 LS4 Vette)
After you check the throttle cable, check for a plugged fuel filter, or stuck mechanical advance weights.
Valve springs could be an issue, but the stock cam is so mild that its not what I'd check first.



I noticed your air/fuel ratios were shown after I first posed. I doubt your fuel filter is a big restriction based on those.

 

There is a lot of restriction through the side pipes - how big is the pipe feeding from the exhaust headers to the side pipes? I'll bet it's pretty small.

 

Wow, very surprising Dean!!! Smells like a body off, LS-9/6-speed install!!!

Just kidding...

Rogman

https://www.corvetteforum.com/articl...ngine-Swap.php

 

It's very easy to lose 30% in a C3 with a T400, especially with a stall converter.

Here are the HP killers:

1) T400 and stall converter
2) Exhaust, stock manifolds and side pipes are major killers
3) Mechanical accessories, especially the clutch fan
4) Carb and ignition performance/air cleaner setup is very important
5) IRS eats up power too
6) Rear tire weight and psi.

My engine went from 657hp on the engine down to 460rwhp on a SuperFlo chassis dyno. So roughly 200hp... And that was with an electric fan that was not running and a full 3" mandrel exhaust system with free flow muffs..

I'd say you have a lot of room for improvement with your current parts, I'd start with the carb operation and work down from there.

 

It is just too inconvenient and expensive to tune on a dynojet. no fun either.
Buy the G-Tech GTP-240 $199
and tune it yourself.
Sell it when done, net cost will be cheap!

 

[QUOTE=ajrothm;1582583201]It's very easy to lose 30% in a C3 with a T400, especially with a stall converter.
/QUOTE]

That year was the worst for HP loss in the big blocks or small block for that matter. With the T400 you can lose 30-40% to the rear wheels. I used to have Gross/Net/RWHP speadsheet for every C3 made. I wish I could find it again but I do remember that year with the 454 lost 40% to the rear wheels ( the most power loss out any C3), through the T400. I was shocked.

The actual gross HP for the motor wasn't very high in the first place, so I believe you are seeing what I saw on the spreadsheet. Now properly tuned and everything running the way it is supposed to I believe your HP should be higher at a higher RPM but not that much.

 

Visually verify that the carbs throttle plates are fully opening when the accelerator pedal is fully depressed. Sounds like an unnecessary thing to do...but it is a common problem that folks rarely check out.

 

For comparison, my original #s matching 350/270hp 8.5-1 compression and 143k miles(new rings/bearings/valve job at 95k) made 195rwhp on the same Superflow chasis dyno that I also used later on with the big block. It made 204rwhp with the hood open, air cleaner lid off and the air fuel ratio perfect at 12.8, timing at 36*.

This was with a Performer intake, stock q jet, 327/350 HP cam(L79) 1 3/4" headers and 2 1/4" exhaust w/flow masters. T400 and stock converter.

The car ran 15.0@91 mph setup like this with 3.08 gears.. 3540lbs race weight.