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  #16 (permalink)  
Old 05-26-2014, 01:35 PM
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Originally Posted by Catfish11 View Post
Howdy folks I am still messing with this.
I believe I have everything real close , no black soot in pipes.
Here is what I have
I am running stock exhaust system with a catalytic converter.
Stock iron intake. (one crossover port blocked / one open crossover port.)
"high performance" ignition curve in HEI. 36 all in by 3000 RPM. Limited vac advance to 16 . Manifold vacuum
4.5 PSI
350 engine
Cam is a stock truck cam. (photo attached on cam)
350 automatic trans
2:73 rear end gears
31" tall tires.

I seem to have it tuned correctly for the most part but I seem to be a little lean coming off idle. I say lean because at idle I am reading 12.5 A/F on a edelbrock narrow band meter. I have tuned idle with a vac gauge and tachometer.
When leaving a red light I get a VERY SLIGHT hesitation and the lights on the meter go out then its fine and smooth and the meter lights come back on. Then I am reading about 13.5-14 A/F at 70MPH. No black soot in the pipes. I seem to have the idle,cruise,and wot correct but still trying to figure out the slight off idle hesitation. I think it might be related to the throttle angle you talked about. From the ignition side of it though I read that full manifold vacuum is best?
Any ideas?
cam specs

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  #17 (permalink)  
Old 05-27-2014, 05:52 AM
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Sensor position is good.

Try 1 or 2 degrees more initial timing and see if it improves. Otherwise it needs a little more pump shot.
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Old 05-27-2014, 04:09 PM
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I did some tuning on my engine with nothing but an UNheated o2 sensor (it's what I had laying around) and a $20 sunpro o2 gauge from the parts store. Like F-bird said (and he's right on the money) narrow band o2 is a great tuning aid IF you know what it's telling you

note: just remembered.. my 02 sensor is mounted in a bung, in my passenger side header collector about halfway between the individual pipes at the front, and the flange at the back. I run a dual plane intake, so the sensor is reading both sides of the carb even on one side of the exhaust.

I have a holley 4150 vac secondary carb.. so my tuning parameters are a little different then your qjet.. but it's the same idea with the meter.

I tweaked my primary jets down until I got a steady reading right in the 'ideal' range on the meter 14.7:1.... then I used a vacuum gauge on the manifold, and the seat of my pants to 'feel' where I felt the acceleration enrichment should come in.. (I had a little bit of a sag before the power valve kicked in) I used the readings from the vac. gauge to pic a new power valve. licked the bog in one.

What really surprised me, was at wot that the meter was hanging out in the 'lean' range.. I ended up going up about 6 jet sizes on the secondaries to get the meter 'pegged' all the way to the rich side.. that may not be exactly 12:1 or whatever the ideal # is (Depending on who you ask, and what fuel you run). but it runs WAY better

I did as F-bird explained, I set my idle mixtures with a vac gauge.

That being said, if you have the $$$ a WideBand o2 sensor kit with a data logger is definitely the kick-***** way to go about this

and funny enough.. after the car sat for 4 years while i did the body work.. and just idled it around the yard from time to time.. it's running like crap again.. o2 meter shows rich ALL the time.. and then swings lean when I open the throttle... and it bounces all over the place when I'm cruising at higher rpm where I've got a bad miss... definitely time to throw a rebuild kit at the carb.. clean it out.. blow it out.. and try to get it back to the way it used to run... (perfect)

Last edited by kc8oye; 05-27-2014 at 04:14 PM.
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Old 05-27-2014, 06:30 PM
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I got the choke working but still working on the other part.
@ idle the gauge shows 12.5
@ WOT the gauge shows 13
@ 45MPH , No Load, gauge goes out
@ 45MPH , with load/up hill, gauge is 13
@ 70 MPH, no load, gauge is at 13

The hesitation I am talking about it very slight and some times I dont even notice any hesitation.
When at a red light I ease on the pedal and the gauge shows 13 and around 10MPH the lights goes completely out, any slight load/movement of peddle the lights come on at 13.

Next I am going to try a little more timing, 1-2

Maybe this is normal for a quadrajet?
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Old 06-01-2014, 12:09 PM
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No open spacer on the stock iron intake. Its a 4 hole quadrajet spacer.

Can you take a look at this and see if i am reading this right. At highway speeds the lights flutter (NO LOAD) and I cannot get a accurate reading. With slight load @ same highway speed the lights are steady with accurate reading. Can I use the "slight load" steady measurement and lean it out a little more at highway speed? If so the lights will go completely out at same speed with NO LOAD.

I adjusted the float level to 3/8" to see if it would make a difference but did not see any change.
I also disconnected the EGR and took it for a drive. Heres what I came up with while using the narrow band meter.
12.5 @ WOT
13. @70MPH slight load, uphill on highway
13.-13.5 @70MPH no load, but the meter is "fluttering" off and on also. I am thinking the metering rods are going into jets at high vacuum(leaning out at no load)

Meter goes lights out at cruise, 45 MPH, but at the slightest movement of throttle the lights come on( seems on the edge of lean)

This is reading the meter no complaints with engine operation through power band. Engine runs smooth, at idle, cruise, and WOT. Off idle acceleration is now smooth also.
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Old 06-01-2014, 01:30 PM
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Worth every penny I paid for it.

MTX-L Wideband O2 Digital Air/fuel Ratio Gauge
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