cruisin'73

iTrader: (8)

No high dollar build here! just a $250 junkyard engine stuffed into a '73 Nova on a budget. Local performance shop had a $50 dyno day and I wasn't going to miss it!

Quick review of specs:
-2001 5.3 with 106K, now 109K’ish
-Completely stock internals
-Edelbrock dual intake
-Used/rebuild Speed Demon 750
-Ebay 3rd gen SS headers, 1 ¾” Primary, 3” collectors
-3” straight pipes to Thrust mufflers dumped at the axle
-Rebuilt TH350
-2000RPM converter
-Original 2.73 gears

The torque was what I expected, but about 400RPM lower than I expected to see it. The horsepower however was less than I expected, and 1000RPM lower then where a 5.3 SHOULD reach peak at!? WTF! I know I am leaving some on the table in carb and ignition tuning, but I expected a peak of about 275HP @ 5500RPM.



Now don’t worry, I am no Dyno queen, I know a dyno is a before/after tool and that kicking asphalt is what is REALLY important. As a baseline I am happy with how it performs on the road and on the track. This summer I am hoping to stab in a 224R or 228R cam, LS2 chain, hardened pushrods, beehive springs and maybe a trunion etc etc. Oh and some better rear gears!


Any ideas what might cause the HP to come in nearly 1000RPM earlier than in a stock configuration? Thanks for the input!

flyjum

Tuning?
Could be running rich?
Needs a cam bad even something like a LS2 cam will wake it up a lot in the top end
Most stock 5.3s dyno around 230~ whp i think
A carbed full exhaust one should do a little better
Have not seen that many stock 5.3 numbers to know but it looks like the torque is falling off pretty rapidly after 4,000 rpm

1989GTA

I don't know what the problem is either. I do agree that a cam will really wake it up. Maybe do a compression test?

DREAMZ28

iTrader: (1)

Yea that just doesn't seem right. Even if its a stingy dyno, I wouldn't expect it do completely nose dive torque wise at 4k..

cruisin'73

iTrader: (8)

I would say yes on a stingy dyno, but the torque numbers seem about right, if a little early in the RPM and falls off real quick. I am questioning if the 750DP is to large and and the secondary is not getting enough signal to pull additional fuel. So once the secondary squirters are exhausted there is a lean condition. Hence the 4K drop off and the small unsteady waves that starts at about 3750.

As crazy as it may sound, I am considering upping the secondary jets in a hope that it will increase vacuum signal.

But I am also working on the carb and ign tune and it is making a big difference in engine behavior already.

I am open to any thoughts or theories. Thanks for the input.

wesmigletz

iTrader: (6)

Have you thought about trying a softer spring for the secondaries? If the carb uses the same springs as a holley, you can by a secondary spring tuning kit. Try a purple or the stiffer of the two yellow springs.

cruisin'73

iTrader: (8)

The Dyno shop sent me a video of the Nova on the Rollers. It sounds pretty good, but a little tame.

CHEVELLEPOSSE

Nice swap look at the carb and timing

cruisin'73

iTrader: (8)

Update: Over the summer I swapped cam/pushrods/springs, added an AFR gauge and got the dyno on the rollers again. Check out the results here:

https://ls1tech.com/forums/dynamomet...-cam-swap.html