Too many times people just speculate about carb tuning! Well here are some hard numbers. I interfaced an oxygen sensor with my Digital Volt/Ohm Meter (on a CARBED car)and drove aroud checking Edelbrocks STOCK Manual Choke 750 carb for proper Air/Fuel Ratios. I ran 862mV at cruise and WOT. Thats is about 13 to 1, just a tad rich. This is on a 420 HP 350 and I find these readings absolutely perfect! Props to Edelbrock. So many people think they have to "Tune" their carbs to perfection, when in reality Edelbrock does a pretty damn good job. So if you have ever wondered if box stock carbs are close then the answer is YES, as long as you follow the manufacturers recommended applications.

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84 Camaro ZZ4 with HOT cam. 1.88 60' (12.98 @ 105MPH E.T.)
Recently Ported Heads, Installed Larger Race-Flo Valves, RPM Air Gap Intake, and 1 3/4" SLP Headers (No new times)
Other Mods: You name it and I have probably changed it.

2001 Dodge Ram Quad Cab 5.9L 4*2

The Bowtie
ASE Certified Auto Tech
LIVE AND DIE BY THE ALMIGHTY BOWTIE!

[This message has been edited by CamaroMike (edited July 12, 2001).]

 

I appreciate you posting real data. We need more of that kind of stuff.

Not to be argumentative, but 13:1 is REAL FAT (did not check your Mv to A/F conversion but I'll take your word for it). Up around 14:1 is "a little rich" for part throttle. And your readings should be significantly richer at heavy throttle than at part throttle. ~14:1 at part throttle and ~12:1 wide open would be what I'd shoot for with the tuning.

I agree that running a little rich is better than a little lean for a street non-emissions performance motor, though.

 

I agree with Damon, thats a tad lean for WOT, and way rich for cruise.

Also I recommend you get a A/F ratio gauge. I used a DMM for that for awhile....but the gauge really works much better.

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"American made baby. 100% American iron. The muscle among the masses. My hero. Yep, you can take your ergonomically designed, space age, computer controlled, 4 door, cup holding map lighted split double wishbone split fold down retractable cargo covered moon roof piece of transportation and keep it. For I have felt the thunder. And I know the difference!"
JSP Motorsports
ICON Motorsports

 

My 1406 right out of the box gave a 12.6:1 A/F ratio at WOT on my 383. That's with a real exhaust gas probe, not just an O2 sensor.

 

Camaromike, I'll be you can still gain some performance with some carb tuning.

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350 with stealth intake, holley carb, 470 lift cam. 700r4 with .5 boost valve, vette servo, tci lock-up kit, B&M megashifter. Richmond 3.73 gears, powertrax locker, timkin bearings, synthetic lube. Custom 3 inch single into 2 2.5 pipes. 1 1/2 drop springs, 1 5/16 solid front sway bar, 1 inch rear bar, custom subframe connectors, custom LCA relocation brackets. Kobel ground FX, current red metallic paint. Lots of other stuff...
82camaro

 

In regards to hooking up the oxygen sensor to a multimeter, I've heard that this is a bad idea. Chiltons says that you can hurt the sensor unless you use a 10 mega ohm resistance multimeter (or something like that). Ditto for either the booklet that came with my new o2 sensor OR my Helm manual. Do air/fuel guages allow for this? (You'd think so...)

I was running 70 jets, and it was averaging 485 or so. I bumped up to 72's and its down to 350-385. I had a multimeter and an air/fuel guage hooked up. Either the sensor got damaged, or my carb is tippin back a few.

 

Chiltons: "No attempt should ever be made to measure the voltage output of the sensor. The Current drain of any conventional voltmeter would be such that it would permanently damage the sensor."

 

Jeez, RELAX! I have done this before on many vehicles and have never had any erroneous problems. Please explain how I could damage the sensor. It is just a coated ceramic that outputs current due to oxygen differences. As long as there is a load in the multimeter then it will not "fry" the sensor.

BTW, did you ever think that a "conventional" voltmeter may be refering to an ANALOG voltmeter. Almost all DIGITAL voltmeters are 10M Ohms resistance and that's what I am using! I don't know if you are trying to be smart but if you are please do some more thorough research before jumping my testing procedures.

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84 Camaro ZZ4 with HOT cam. Ported Heads, Installed Larger Race-Flo Valves, RPM Air Gap Intake, and 1 3/4" SLP Headers (Best 60',Quarter Mile, MPH) (1.88, 12.91, 106.77)
Other Mods: You name it and I have probably changed it.

2001 Dodge Ram Quad Cab 5.9L 4*2

The Bowtie
ASE Certified Auto Tech
LIVE AND DIE BY THE ALMIGHTY BOWTIE!

 

This is a perfect example of my "worst tone" theory. For some reason, when reading a written message, people more often then not seem to infer a negative/aggressive tone, whereas this is not often the case. No offense to you, just an observation on human nature.

As to my message, I guess I phrased it wrong. I was giving information I had read, and wanted to know what other people knew about this.

Thanks for the info, I havent been around voltmeters long enough to think that 'conventional' meant anything other than a cheaper voltmeter... That does makes good sense...

 

X5 speaks of the older style needle-type multimeters. Chilton's just hasn't done a good job of updating their manuals for the times... I don't believe you could BUY an Ohmmeter with the improper resistance but you could sure find one a d USE it by mistake, I guess... In general, if it is newer and digital, you are good, BUT the refresh rates of the digits make it pretty useless, that's why a nice O2 LED monitor was mentioned. Once you try one, you'll NEVER use that multimeter again... I use Edelbrock's... Good stuff.