TPS vs MAP AE 7427 $0E

[CDeeZ]

My Assault racing heads have a nice fast burn style chamber and like timing. The Vortecs I have tuned like about 12° at the minimum.

You are thinking wrong. The old swirl ports like less timing than Vortecs. About 26-28° is all they need.

Also you likely need to change the shape of your AE tables. Progressively higher values with bigger TPS/MAP delta's. Ease off on the lower values if it is getting rich at slight throttle changes.

Must have gotten really lucky on the LS. I had the Express van with the 0411 run 5.7 dialed in very well. I went from the factory converter to a looser converter. All of a sudden it started lean popping if you smacked it to the floor. I ended up adding both timing and AE to fix it. After it rapped up much quicker.

Even port fuel setups can lean pop. Its not a TBI or Carb only thing.

https://youtu.be/gNyr_Z6Q_ck

Well, more efficient heads require less timing. Or so I've read anyways. That's what got me to thinking that. But, I believe you. It really seems like based upon what you're saying, that with these Trick Flow aluminum heads, that this setup can really benefit from some more timing. I will sprinkle some in today or tomorrow and see what happens. I built this 355 with forged pistons. Since it has forged pistons, I might just slug the entire spark table up 5 degrees and see what happens in the knock retard.

What exactly would be a good proportion for "progressively" higher values in the Delta MAP and TPS AE tables? Thinking maybe something like bump the first 1/3 of the tables up 25%, the middle 1/3 of the tables up 50% and the last 1/3 of the tables up 75% or something similar?

The S475 LS has a frankensteined 32 spline T56 built by yours truly. Might have been an issue if it was an auto with a loose converter.

Oh yeah I'm sure. TBI or carbs seem most susceptible to it, to me anyways. LS has the injectors nearly right behind the intake valves. TBI or carb being all the way upstream of the incoming air, seems like either system would be more prone to lean popping as the fuel would be more likely to fall out of suspension and wet the intake walls....

When you change your AE tables both MAP and TPS, are you moving the whole table up and down or are you playing with the curve?

Well so far, I have usually been slamming the entire tables up by a percentage. RBob and several others on TGO have posted about multiplying the entire tables by 10% to 30%... I can now see the potential benefit from adjusting the curve rather than moving the whole table up..

[1project2many]

Well, more efficient heads require less timing. Or so I've read anyways.

They do. Max timing on the older Bowtie race heads was around 36-38 degrees. Vortec are generally run with 32 degrees.

Trick Flow aluminum heads

Aluminum is the key. Aluminum heads transfer heat out of the combustion chamber more quickly and it takes longer for the reaction to occur. So you have to start spark sooner.

I can now see the potential benefit from adjusting the curve rather than moving the whole table up..

Correct. The shape of the curves needs to be adjusted to match the engine's needs.

[PlayingWithTBI]

Chamber design has come a long way since the days of the first smallblock. The size, shape, depth of the chamber all play a part in efficiency. Today engineers are looking for faster and more complete combustion and heads with a well designed chamber need less spark advance. Look at some of the old and new designs in this link: https://www.chevydiy.com/chevy-small...-fundamentals/ If the Summit heads are a copy of an old design head, you may need to add a bunch of spark timing. If they are a newer fast burn type chamber the increased efficiency may work to balance the heat loss through the head in a way that lets the stock L05 timing work. My comment wasn't necessarily about curing popping with timing changes, but more of a comment on how close the stock L05 tables will be to correct.

Here's a picture of the chambers in the Summit 162108 heads CDeeZ and I are using. From what I can tell, based on your link these are the newer "fast burn" style?

Trick Flow Chamber.JPG

[Fast355]

Here is the design I run.


9.6:1 350
271/284 @ .006
215/224 @ .050
.578/.578" w/1.7 rocker
110 LSA
106 ICL

Idle = 24* BTDC @ 750 rpm

WOT
12* @ 800
16* @ 1,200
20* @ 2,000
24* @ 2,400
28* @ 3,000
32* @ 3,600-6,500

Cruise timing is up to 48* BTDC @ 3,000 rpm and 40 KPA MAP.

WOT air/fuel ratio is 12.5:1 near peak torque and leans out to 13.2:1 at higher rpm

Cruise air/fuel ratio is stoichiometric or up to 16.5:1 in highway lean cruise.

[PlayingWithTBI]

Nice, are you going to put your new marine intake on this setup?

[Fast355]

Nice, are you going to put your new marine intake on this setup?

That is my plan. Will have the intake ported first.

[Fast355]

Will also say I was working on an 0411 running a stock long block LQ4 6.0L with an Edelbrock Proflow intake, stock manifolds and 3" dual exhaust in a 1971 Chevelle last night. Cruising around with the stock timing map it was running 48-50* of advance at 2,500 rpm @ 70 mph and that car gets about 25 mpg highway. Pretty impressive for a big car with a 4L80E and 4.10s. That was closed loop with the VE and MAF tables calibrated to a point the fuel trims were staying within +1 and -2%. It had been running a bit rich in the -10 to -15% range. After tuning it smoothed out and just flat ran great.

[1project2many]

Here's a picture of the chambers in the Summit 162108 heads CDeeZ and I are using. From what I can tell, based on your link these are the newer "fast burn" style?

Trick Flow Chamber.JPG

They're a much better chamber design than many of the earlier heads. The spark plug is angled toward the exhaust port to reduce intake shrouding, the chamber walls appear to be slightly tapered at the intake valve to improve flow, and the shape of the chamber appears to encourage swirl during combustion. I would expect these heads to require less spark advance than most of the pre-80's heads.