Got the Nova on the rollers last weekend at a Dyno Day put on by a local performance shop. It went well, but it makes me think I have an issue that need to be investigated:

Quick review of specs:
-2001 5.3 with 106K when installed, now 109K’ish
-Completely stock internals
-Used/rebuild Speed Demon 750
-Edelbrock dual plane
-Ebay 4th 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



Diagnosis:
-286LBFT @ 3800rpm is pretty awesome! And just about right in line with all the junkyard engine dyno tests the magazines have published.
-233HP @ 4600rpm seems about 40HP low and 1000rpm early?!
-It seems that both numbers lose their momentum and start falling off after 4000rpm.
-I think if power did not “give up” after 4k, that torque would hang out longer near the peak, and HP would continue to climb to a peak around 5500rpm
-What would cause the engine to "give up" above 4k PRM?
-Secondaries not getting enough signal to pull adequate fuel?
-Secondaries are drowning out engine?

Here are my current settings:
Carb:
-Jets: 74/78H
-Squirters: 35/35, white cams
-Power Valve: stock and can not decipher rating

6010 settings:
-15° initial
-20° at idle
-rising to 36° by 1800rpm
-No MAP timing

Based on my experience and research on the carb section, here is what I am considering for the carb and MSD:
Carb:
-Jets: 68/74
-Squirters: 31/35, ???? cams
-Power Valve: At idle I am making 21HG, so maybe a 9.5 or 10.5?

6010:
-10° initial
-20° at idle
-rising to 36° by 1800rpm
-10° MAP, dropping to 0° by 11

I would greatly appreciate any questions, suggestions, theories you guys can may have. Thanks guys!

 

In my opinion with a stock cam, stock converter and 2.73 gears your car is nowhere near loose enough to digest what a 750 double pumper is throwing down its throat and your lower rpm numbers reflect this.

Also do you have a map sensor? 36 degrees seems pretty excessive if you ask me. I would try something in the 32 range and possibly taper that off to high 20's above 5k

This said and up till a week ago I was oblivious to this but if you're not using a wideband you're just as well off at guessing.

My current carb is a 670 vacuum secondary and I'm pulling my best AF# and it's running best on 68/69 jets one 35 squirter and no powervalve. That's with a pretty big cam, 2700 stall and 3.27 gears on short tires in a 2800lb car. So take this and just imagine how rich your engine is with that much MORE fuel and that much less of an ability to use it

 

Look up the jetting specs for your speed demon, the as delivered from BG specs. Compare them to what you have in it. And go from there. My next suggestion is to invest in a wideband O2 setup.
As for Power valve, you want a 6.5 in there unless you have a wideband telling you otherwise.
As for timing, I like fairly agressive curves. I would keep it at 15* from 0rpm to 1or 200 rpm below your idle speed, and have it at 32 from there through top rpm. You can play with that a bit and see what it likes when you go to the track. I suspect it will like 34* after you test.
I think you should get yourself a Map sendor as well, and at thst point re do your entire timing curve and build a map curve.
You can use a map sensor from any ls chevy truck . I hot mine from the junkyard

 

You both hit the nail on the head! I am trying to save pennies here since we have a kid on the way, but I know I’m going to be chasing my tail without one. Haha, I bet I would spend less on a AFR gauge then I would on parts and poor MPG trying to live without one.

Also, yes on the MAP sensor, I had a spare truck intake that I pirated the MAP from and installed last night. So with additional MAP would you recommend:
-0 to 500=10°
-500 to 1000=ramping to 22°
-MAP=10° falling to 0° around 11 PSIA

How’s that sound for a starting point? That would keep total timing around 32° most the time, and be tolerant of lean or rich conditions.

 

My map curve is super simple. It's 10 degrees starting at my flat n level optimum cruise speed and 0 the 1psia step lower

 

Drive the car with a laptop hooked to the msd, and note the map readings at idle(plus idle rpm), idle in gear ( plus that rpm), and at cruise speed( and that rpm).
Once you know what map psi it runs at you can configure a decent curve.
10-12* will work well from 0psia through somewhere around 8psia, then taper out to 0* at about 12psia.

 

Thanks guys! This is a great start for my ignition curve. I even brought the laptop to work today so I can take the long way home and work on the tune while enjoying a rare sunny Washington spring day!

Sounds like hard work though, I bet the car will need a break to cool off on the way home and I know just the bar!

 

Innovate MTX-L wideband is on the way! Very excited, but I feel like a stalker peeking out of the garage every time I hear a diesel truck idling by!

Further refining my fuel and ignition tune has improved the cars behavior. Nice idle, just a small stumble off idle and small stumble at low speed tip in. Going WOT from idle or low speed has a small stumble, but then quickly starts laying black patch. Cruise is smooth. Tip in or WOT from cruise is pretty sharp and the power comes on quick!

Double checking my accel linkage and I found no slop BUT instead that the bolt was adjusted almost ½ way through the accel pump range. I backed off the bolt until it was just at the top of the range and now the pump shot is much larger and longer. And what guy doesn’t want that. I also moved the white cam to the more aggressive #2 position, and that cured much of my stumble. I am running 35 squirters front and rear and it seems happy. I tried to step down to 31 in the front and the stumble became much worse. I’d try bigger, but don’t have 37s.

3Pedals’ ignition recommendation was pretty close to spot on and the addition of the MAP timing really helped throttle response through-out the operating range. I may play with the tune a little more, but I think I’m going to call if good until the AFR gauge is in.

I have even been thinking about a little lo-tech data logging…the MSD program has a realtime tach, vac gauge and total ign timging gauge, and the MTX-L gauge is capable of plugging into a laptop for data logging. If I found some cheap simple screen capturing software I could collect all 4 points of data for review.

 

Innovate makes a small data logger designed to work with their gauge. It has multiple channels that take a tach signal directly or things like a MAP sensor or TPS sensor. Their display software is very nice, you can do a lot with it.

 

Everything everyone is suggesting is very good tuning tips and will def help I getting it run the best ya can, however, peak hp at 4600rpm?! 100k mile ls motor, that you know of, could be a lot more. That just screams valve springs are shot to me...if it were me, my next move would be fresh springs and some hardened pushrods. I'm sure you plan to cam it at some point so you will need to do this regardless. Also, I've said it in another thread of yours, but im willing to bet those mufflers are hurting power too...

 

Pops’

The Innovate system is very flexible/expandable beyond a simple gauge. That and the price are the reasons I chose it.

I was sharing this datalogging idea with one of my buddies who is develops and tests heavy truck control software. Together we are investigating using several free internet downloadable data capture programs to collect, and display the input from the MSD and MTX-L. It would provide realtime display in a text format, which is not very useful. But that data could then be converted into graphs for review. Nerdy indeed, but a very powerful tool.

 

Toxic

I agree that there is SOMETHING missing from the top end to cause the engine to “lose momentum” after 4K. Also there is that “ripple” that appears in both the TQ and HP curves about 3800. I am not sure if it is a loss of valve control though. It is normally very evident on a dyno graph when valve control becomes an issue. Things like dips and flat spots that last several hundred RPM. BUT, are the tired old springs helping? That’s a big NO. I have a set of Comp 918s waiting for duty on my tool bench, and changing pushrods will add about 1 minute to the job! Good call. I’ll start searching for a budget set. I do plan to stab a cam in there at some point. The front runner right now is a TSP 224R or maybe a 228R. Something big, but not huge. And of course the 2.73s will be coming out in favor of something higher. Thinking 3.72s maybe?

I do recall discussing your concerns with my exhaust somewhere before, where was that? In my build thread? Regardless, yes I know that straight 3” pipes to essential 40-series mufflers may not be primo, but what is your concern? My only worry is that the system is too large = lack of back pressure = reduced scavenging. Thanks Toxic, friendly criticism is always welcome!...Dont tell my Wife I said that though!

 

Swap the springs and rods out and see where you at. If you can get back to the dyno and see difference. I'd prefer track times, would be cheaper anyways. As far as the exhaust, doesn't matter how big pipes are if they dumping into corks. Choke masters didn't get their nickname for nothing 😜. And im willing to bet those thrush mufflers are no better if not worse. This theory could easily be tested as well at track. Just unbolt pipes and swing them to side an make a pass. What could it hurt? Go faster?! Lol anyways, every car I've had went way faster when I took off or bypassed the choke masters. Jmo

 

The shop just sent me the video on my Nova up on the rollers. Is it just me or does it sound like it is hitting a wall and and climbing pretty slowly?...


AFR gauge has arrived and I hope to get it installed in the next few days. I am very excited to hopefully get my tuning on the fast track now!

 

Looks like a cam/pushrods/springs and AFR gauge were just what the doctor ordered. The Nova is a little terror now and I am in LOVE!. The feel and the sound are perfect and I feel little-to-no sacrifice in streetability.

-TSP224R .581”/.581” 112LSA
-Comp Chromoly 7.400” pushrods
-Comp 918 springs
-Innovate Wideband AFR gauge

The dyno shop had another dyno day so now I have before and after results! I combined the before and after into 1 graph for easy comparison:




Here is the vid of the July run:
*They tried to run the in 3rd gear on the first run. That dyno must have been at about 160MPH! haha. The second run was in 2nd and ran the engine up to 6500RPM.


Thanks to all that shared advice and time!

 

Holy Freolies. Now that is an upgrade you will feel.

Stock 5.3's are known to have weak valve springs, but I think you need to put Toxic99 on your Christmas card list.

 

No kidding! The sound is nice and rowdy, but not enough to get Johnny Law's attention. Really the engine acts almost stock until 4K and then it starts to sing. Even with my 2.73 gears it wants to rip the tire lose, and I have to get off the pedal or the shift into 2nd is a 50mph smoke show! Time for a posi and better rubber!

 

Nice gains! Looks like the 224r cam was a great choice.

Time for some gear and converter to take advantage of the major HP/TQ gains now available from 4K-6.5K

 

That's not bad. Makes me impressed my 4.8 with a 220/220 cam and .510 lift made 312 and 308. Has better heads though.

 

Gears are for sure happening over the winter, converter MAY happen. Pulling the motor in my tiny garage and sloped driveway would not be fun!

Thanks Zone! I could round up a few ponies with continued work on my fuel and ignition tunes, but I think the small valve 862 heads are the hold back now. I have been talking with Agearhead4life about a 5.3 that he built with an LS6 cam and 862s with LS1 valves and a home port'n'polish that turned 330hp. That may be the route I decide to follow.