Tuning a TBucket Dart 400 cuin Engine

I think he can easily get in the 10 second. and hes probably near it. if he can get some traction.

Am not a fan of too lean idle, maby because of the big plenum area from the blower, but i need a slighly rich idle to get good throttle response.
 
I think he can easily get in the 10 second. and hes probably near it. if he can get some traction.

Am not a fan of too lean idle, maby because of the big plenum area from the blower, but i need a slighly rich idle to get good throttle response.
It depends if Rick can control the T or not.
He is short shifting now..
No Rollcage or Roof over his head if the T gets airborn or if the Rear suspension breaks.
Best to be at the dragstrip.
Safety crew present.
 
boosted applications almost always require a richer fuel/air mix ratio,
n/a applications tend to foul plugs if the idle below about 2000rpm runs near 12.7:1 f/a ratio where max power is generally found
while every engine will require custom adjustments, the basic starting points will hold remarkably consistent
start by doing a compression test , and all cylinders should be within 7% max,and by verifying TDC and your timing tabs and damper reflect true tdc.
set the carb floats and verify your getting near 5 psi of consistent fuel pressure and ideally your using a fuel pump that can supply at least 50% more fuel volume than your engine requires with,the engine at max loads at max rpms
Idle- up too about 2500 rpm try for 14.7:1-15:1 f/a ratio
from about 2500 rpm- too about 4500 rpm try to smoothly and predictably transition the fuel/air ratio mix richer to about 13.5:1
from about 4500 rpm- too about 6500 rpm and higher ,try to smoothly and predictably transition the fuel/air ratio mix richer to about 12.5:1
your using reasonably fresh spark plugs with a .043 gap, ignition wire with a ohms lower than 500 ohms a foot resistance,the exhaust back pressure is less than 1 psi at peak rpms.

this is only a starting point on the engine tune but it generally gets you in the ball park and tends to reduce the chances of the engine reaching detonation conditions.
the ignition advance curve needs to be checked,the electrical grounds are checked,
your engine is running at least 10-15 psi of oil pressure per 1000 rpm with the correct engine clearances and your alternator and battery provide consistenly 13 plus volts at idle thru max rpm


volumetric.gif

FuelFlowDiagram02a1.jpg

Stoich.gif


chart3e.jpg





http://garage.grumpysperformance.com/index.php?threads/carb-tuning-info-and-links.109/

http://garage.grumpysperformance.com/index.php?threads/setting-up-your-fuel-system.211/
 
In your post #175 you suggested I lean out the primary main jets by one step, so that's
what I did. I went from a #71 to a #70.

Looking at the graph there seems to be a delay between a dynamic throttle position and
AFR. Notice how the throttle is wide open at 4.5 seconds, but the AFR doesn't stabilize
until 5.5 seconds on the graph or about a 1 second delay before the changes in throttle
position actually show up in the AFR.

The lean spike at 2.2 seconds might be the same as the slight hesitation I feel at tip in
during cruise. This all came about during the IAB adjustments. I'm wanting to go from
the .081" I have now to .074". I think it will get rid of the lean spike at 2.2 seconds.

Grumpy_2015-09-18-1500.jpg
 
normally a longer duration shot , or longer and larger volume of fuel from the accelerator pump through the squirters, compensates for and eliminates that,partial momentary additional gulp of leaner air during the rapid change of vacuum in the plenum due to rapidly opening throttle blades, at the start of the transition, Id look into adjusting or replacing that accelerator pump cam, ID try the BLUE ONE, then maybe GREEN
http://garage.grumpysperformance.com/index.php?threads/holley-accelerator-pumps-cams.1790/

http://www.summitracing.com/parts/hly-121-37/overview/

http://garage.grumpysperformance.com/index.php?threads/holley-carb-power-valves.1639/
This chart gives the pump shot volume in CCs for each cam in each position.

Position 1 Position 2
White 17 19.5
Blue 18 20
Red 18.5 20
Orange 19 24
Black 19 18
Green 24 30
Pink 30 37.5
Brown 36

hly-20-12_cp.jpg

holleyfuelpumpcamn2.png
 
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Ran the very same test for gas mileage using the same pump and the same
path as before. Drove 49 miles and used 2.5 gallons of gas, which figures out
to be 19.6 MPG. The AFR meter was showing 14.5 to 15.0 most of the time
during the drive.

That's an increase of 5 MPH (19.6-14.6) at 65-70 MPH.
 
well thats certainly decent mileage but my first question is DOES it run correctly and have nearly instant and consistanly repeatable throttle responce,
I'm sure theres ALWAYS a few areas that can be checked,verified, modified,and improved.
As Im sure your becoming aware, engine tuning is about 80% science, that you can test and verify,
about 10% art,or skill thats developed over time, and 10% intuition based on previous experience.

and by now that engine should have enough power to easily spin the tires if you apply a bit more throttle than required to at least 40-50 mph, and your aware that all gas brands change octane and additive formulas several times a year and that octane varies between brands and between batches made.
(obviously tires , type of road surface,and suspension being set up correctly could be a factor,)
which I can assure you that engine should be fully able to do once correctly tuned,
having built similar engine combos several times in the past.
youve done a spectacular job and you do damn impressive work,
in fact so good I wish you were local so we could work together!
frankly its rather rare to find someone willing to do the research and listen to experience
(one reason its also rather rare to see guys build impressive engines , with properly matched parts with proper clearances etc.
rather than assembling , out of the box, over the counter, and frequently mis-matched parts)

so I'm sure you remember that before we started this engine build we discussed your intended use of the car and the engines basic requirements,
and it was never intended to be a true race engine!
HOW DO YOU FEEL WERE PROGRESSING at this point,
and WHAT WOULD you change or want to work a bit more on?


yes as we discussed awhile back theres still things that might be changed to allow you to build a bit more horse power rather easily,
but generally at the cost of less use or easily driving the car in traffic for long periods at lower engine speeds,
As Im sure youll remember , as we entered into the engine build goals we discussed ,the combo was not designed as a race car engine ,
http://garage.grumpysperformance.com/index.php?threads/tbucket-engine-project-dart-shp.3814/
but rather, youve built a good dependable performance combo with both good durability decent street manors,
and rather easy low 11 to high 10 second potential in that car.
you've avoided a very common mistake I see guys make frequently, and that is looking only at the peak horse power numbers ,when planing an engine build, or reading those magazine engine build's that frequently, and conveniently,try to sell some manufacturers parts,that don,t tell you about 90% of the machine work, time and care required in true engine building, vs slapping parts together,that point mostly to the peak power numbers,that might get used 2% of the time, mostly for bragging rights,If your experiencing detonation the fuel/air ratio your engine is running , the fuels octane rating,it runs on may have and very likely did get lower or the fuel/air ratio , leaner
and ignoring the fact that a street driven car engine must have durability and dependability,and have instant massive available torque ,
and peak power is a very seldom used factor on a street car, engine.
that peak HP, seems to get far more attention .by many guys, than having a huge flat instantly available torque curve available under your right foot, which can be used 98% of the time.
 
I agree with Grumpy Rick.
The T is not set up to Drag Race to 11's & 10's.
I worry about the rear suspension taking long term abuse.
4-link be best.

Let me go after the Hellcats.
My 1970-1/2T/A RAIV Is already setup for Drag Race Duty.
 
enough power to easily spin the tires if you apply a bit more throttle than required to at least 40-50 mph,

First gear has no problem spinning the tires, but once it's in 2nd gear not so much.
That's with a 3.7:1 rear gear, traction lock and 31 inch diameter tires.

youve done a spectacular job and you do damn impressive work,
in fact so good I wish you were local so we could work together

That truly mean alot to me coming from you Grumpy !

HOW DO YOU FEEL WERE PROGRESSING at this point,
and WHAT WOULD you change or want to work a bit more on?

Progress seems to be in spurts and sometimes undetectable, except by instrumentation.
Measured in tire spin, all the little changes have added up to a big change in off the line
response. It's after that, that the little changes are not as noticeable by seat of the pants.
At least by me, I have to rely on the AQ-1 to tell me.


Not sure there is anything that I would change and do differently, except move to Florida
so your experience would be easier to tap.

.
 
2016-08-28

The problem is at tip in during a 65-70 mph cruise, such as starting to negotiate a
slight incline. The AFR goes way lean to 16.5-17.0 under very light load and starts
detonating. NO DATA LOGGING WITH THE AQ1, JUST AFR OBSERVATION.

Idle Air Bleed - IAB Now = .074" (49) TO .040" (60)

Would hardly idle, way to rich, then I adjusted the idle mixture screws to obtain a
14.0 AFR at idle. They were ¾ turn out. No driving test was conducted before the
next change. IAB = Idle Air Bleed.

------------------------------------------------------------------------------------------------------

IAB Now = .040" (60) TO .064" (52)

Idle mixture screws are 1.25 turns out, AFR 13.5-14.0. During driving test on highway
and easing into the throttle the AFR was still going too lean, but better,
AFR = 15.5 - 16.0. Detonation is less, but still there, slightly less audible.

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09/03/16

PriMainJet Now = .070 TO .072
Note: Power Valve = 7.5
Ambient Temperature: 90°F

Detonation is much better, but there is still a slight note of pinging sound under very
light load. AFR is running about 14.0 under light load. Pinging only happens with
torque converter locked up.

My next step will be to go back to the ignition timing advance curve, returning to my to
the light-silver/heavy-silver springs. Then backing off on the Total Timing from 35° to 33°.
 
from what youve stated backing off on the advance curve on the ignition will more than likely help, but I think I'd also go one step richer on the power valve, you want to keep the r/a ratio fairly lean at idle lets say 14:1-14.7:1 but smoothly and consistently transition to about 13:1 to 13.3:1 by 3000 rpm then slowly transition to about 12.6:1 at 5500 rpm and up. to reduce the engines tendency to detonation under load
Stoich.gif
 
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My next step will be to go back to the ignition timing advance curve, returning to my to
the light-silver/heavy-silver springs. Then backing off on the Total Timing from 35° to 33°.

When did you switch back to the blue springs? On pg 8 you had light-silver/heavy-silver springs.
I think you might now be at the point of going in circles Rick with so many variables to test, analyze, make a change, and test again.
If you don't have grey hair already, you will by the time you are done (or bald).;)
But your fuel delivery system is inadequate and cannot keep your float bowls filled to the proper level.
This is giving you inconsistent results and leans your A/F ratio automatically as the bowls empty.
This will affect the tip-in points of the many circuits in the carb.
Ask me how I know. Along with a few other problems, my 84 TA also had inadequate fuel delivery.
It was using an electronic quadrajet at the time (really small fuel bowl). You have 2 large ones.
Making 1/4 mile runs on the highway, after I shifted into D at around 90 mph, the engine would stop
like someone turned the ignition off. Pedal still to the metal and slowing down. Then it would sputter
and pick back up and finish the run. How LEAN do you think I ran? By the time I figured it out I already
had bigger problems. I thought for sure that I damaged the pistons from detonating too many times because
I was now spraying oil out of the tailpipe and obviously fouling the plugs in short order. My testing revealed that
the stock fuel lines themselves were a major restriction. Bigger block-mounted fuel pumps didn't make a difference.
To overcome this for the time being, adding a small electric fuel pump at the rear of the car to give the fuel a push
up to the block-mounted mechanical worked as a band-aid.

I realize you plan to redo your fuel system this winter, but how is it set up right now? Is it dead-headed, or are you
using a return line. Does your tank have a vent to let air in?
I think that Holley RED pump might be shot. If you are using a regulator, plumb it in after the carb
and installed backwards (return style). This way the regulator does not add yet another
restriction to the fuel supplied to the carb.
 
from what youve stated backing off on the advance curve on the ignition will more than likely help, but I think I'd also go one step richer on the power valve, you want to keep the r/a ratio fairly lean at idle lets say 14:1-14.7:1 but smoothly and consistently transition to about 13:1 to 13.3:1 by 3000 rpm then slowly transition to about 12.6:1 at 5500 rpm and up. to reduce the engines tendency to detonation under load
Stoich.gif
I agree with Grumpy 13.5-14.0 maybe to rich at idle, maybe going to .054-.058 on IAB and maybe 8.0-8.5 on power valve, timing - maybe all in by 3000, test it, then if needed drop to 33 degrees total timing. I would test it with the faster mechanical advance first before dropping the total to 33 degrees, I am not sure about dropping the total timing and the mechanical advance change . I was wrong about my overlap today when I said 63-65 mine is 60 degrees, I may have to run a little richer but not much.
 
Rick, I was reading some of Grumpy's links and found this:
transferslot2b.jpg


BTW on carburetor equipped engines 5.0psi--5.5 psi at the carb inlet port is about ideal.
YOU CANNOT JET OUT A MOMENTARY LEANNESS CAUSED BY AN INSUFFICIENT FUEL SUPPLY IN YOUR CARBS FUEL BOWLS, THE WRONG POWER VALVE,OR ACCELERATOR PUMP CAM, or the CARBS TRANSITION CIRCUIT THAT WILL NOT SHOW UP IN A NORMAL PLUG COLOR READING. !!!
 
Thanks Loves302Chevy for thanking about me. I don't believe I have a fuel delivery
problem at cruise condition, fuel volume needed is low under such conditions. At WOT,
then yes, I most likely have a problem then.
 
again, the fast and pragmatic answer is that local fuel octane levels change with both the brand and time of year, and youll be forced to make a few changes, like richening the F/A ratio and reducing the ignition advance and of course the easy answer is buy higher octane fuel.
even my neighbors complain, when his 440 road runner runs like crap during the summer months, and he has lower 9.7:1 compression
you may and in fact are very likely to find youll need to either run high test from a different fuel source or add octane boosters if your current fuel octane is to low.
I found that the local mobile and texico have very obvious seasonal octane changes in my local fuel source I use for my corvettes.
part of the year thier 93 octane runs fine, but durring the hotter months I need added octane boosters. like adding 4 oz of MMO and a gallon of (toluene) to a tank of 93 octane
 
09/04/16

Changed the distributor advance spring back to the light-silver/heavy-silver. This slowed down the advance, all in by 3500 RPM. After a 50 miles test drive, the problem is still there with little to no change. So I'm not sure that retarding the ignition timing from 35° to 33° is going to help.
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09/05/16

PriMainJet Now = .072 TO .075
NOTE: PVCR = .067” (51) They can’t be drilled any larger for an 8-32 set screw.
Test drive didn’t show any improvement in detonation, although the AFR was in the 13.5-14.0 range.
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One observation I have is the fuel curve seems to be much flatter as I ease into the throttle now with
the richer PriMainJet. Looks like I can backup to a PriMainJet of .074 and regain some of my fuel
economy without changing detonation. Will just have to run without a the torque converter locked up
when I'm running over 70 mph in the heat of the summer. At least until I decided to get back into the
motor and retard the cam timing.
 
I really wish I was able to stop by ,(regularly) as if you were local,
, simply because the tuning issue should be rather easily modified ,
to match your desired fuel/air ratio curve.
Engine tuning is mostly science and a bit of art and experience.
as long as you have steady and consistent 5-6 psi of fuel pressure at the carb inlet port,
and your not seeing any significant exhaust back pressure,
between your ability to change and test,
power valve's, and your ignition advance curve
primairy and secondary jets,
squirters, and cams for accelerator pumps,
theres not a great deal that can,t,
be compensated for with experience,
your access to a fuel/air ratio measuring gauge should make tuning much easier since you can see the result of changes AND use the spark plug condition and narrow the potential choices
 
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as long as you have steady and consistent 5-6 psi of fuel pressure at the carb inlet port,
Under constant cruise condition, I believe my fuel pressure is constant. WOT is a definitely another story.

and your not seeing any significant exhaust back pressure,

My back pressure exhaust test was approaching 4-5 psi. I hope to change my headers to a new Tri Y system from Schoenfeld.
Back Presure Test:
http://garage.grumpysperformance.co...gine-project-dart-shp.3814/page-89#post-46858
 
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