Engine Tuning

[hondarider188]

I am looking to get the most out of my engine like everyone else when it comes into the fuel economy. And i dont have any idea on how to tune my engine to get good mpg. I have a 1983 chevy k10 with the 350 and a edlebrock intake manifold and carb. with the high flow triangle air box. And the main thing i need help with is that i dont know where the air/fuel mixture screws should be at and the same for the idle. The truck runs great and starts good but i would like to get more out of it. The last thing is the choke, it has been converted to manual and i do need to use it to start easier in the cold cold mornings but shouldn't the engine be able to run with the choke still on? for my doesnt but kills the engine.

[Fairlane514]

You can use a vacuum gauge plugged into a port with full or "manifold" vacuum to tune the idle mixture screws. Your goal is the highest vacuum reading. You can also check your timing, initial should be around 10-12 degrees with the vacuum tube disconnected and plugged, then reconnect after you time it.

Yes, it should run with the choke on. It may be possible you have the idle mixture screws "off" enough to cause problems.

You didn't say what carburetor you have...................I'm guessing Edlebrock?

[Tazman]

Have you given thought of going to a throttle body injection like the 87's have?

[hondarider188]

Yes my carb is an edlebrock, but i dont know what size it is or how to identify it. and i havnt thought about the throttle body injection, but i would think that the conversion would cost alot.

[gildardo01]

i dont think that converting a carburated engine into an injected engine is very feasible... by spend over a thousand dollars just to gain 2-3 mpg... a well tune carb engine can give the same results as an injected engine...

[DanInMichigan]

No disrespect,  but I think you're fooling yourself if you think you can get a carb to perform like injection.

About the best you can get with a carb will probably be by using what GM put on it and modifying everything else to be more efficient, like the exhaust and friction reduction measures.

The factory had many years of engineering and testing to design and tune their carbs.  They usually work pretty well.  Buying an edelbrock, holley, or even a quadrajet that was not calibrated for your engine will end up being a compromise.

Take a look at the Holley on a 1985 mustang GT.  Very highly tweaked version of what summit racing sells.

Dan

[gildardo01]

check out this article... http://www.chevyhiperformance.com/tech/engines_drivetrain/induction_poweradders/0510ch_carburetor_tuning_gas_mileage/viewall.html

[Fairlane514]

Interesting article, too bad it doesn't address qudrajets

[gildardo01]

Interesting article, too bad it doesn't address qudrajets

true... but 21mpg as stated in the article is not bad for any old v8

[DanInMichigan]

I have a narrow band O2 sensor now installed in my header pipe and it's of limited usefulness but I plan to get a wideband towards the end of this month.

I actually have fully adjustable air bleeds in the carb body(s), I have 6/32 brass set screws, and a tap that I used to install them into the metering block for full control over my IFR.  I have a box of jets, a boatload of squirters, a downleg booster body, an annular discharge booster body, a vacuum gauge installed on my dash, quick fuel e85 metering blocks (I've run e85 for a bit) and lots of time sitting under the hood pulling changing parts (one at a time) to tune.

While I won't claim that 21mpg is impossible in a car with a cam over 250 degrees duration @.050 and a holley, I think it's probably extremely rare.  I gotta say that just because a magazine says they did something like that I hesitate to take it at face value.  It looks like something that sells magazines.  I'm not arguing that carbs can't be tuned, but that it is very difficult and time consuming to tune them to work as well as fuel injection.   The carb in the magazine article didn't even have a choke.

Dan

[bake74]

No disrespect,  but I think you're fooling yourself if you think you can get a carb to perform like injection.
Dan

     I have to agree and say that it is not as easy as everyone says to tune your carb only to get great mpg.  It is a little bit more involved.
   
 

You can use a vacuum gauge plugged into a port with full or "manifold" vacuum to tune the idle mixture screws. Your goal is the highest vacuum reading. You can also check your timing, initial should be around 10-12 degrees with the vacuum tube disconnected and plugged, then reconnect after you time it.

     This is the best for you are your current level of understanding.  It is admirable that you acknowledge your limited understanding.  I encourage you to learn all that you can.
     Your choke is there to help cut off air flow (basically) until the carb has warmed up enough to atomize the fuel properly.  With a manual choke it could be you do not have your mixture screws set properly, or your manual choke is not adjusted right, so when you pull it and think it's closed off it really is not, or both.
     Also as DanInMichigan stated, you could spend months resetting, retuning and messing around and never match what EFI can give you.  Just got to take it as it is and shoot for the best outcome you can get.

[hondarider188]

thanks for the help guys, what is am still wondering though is that are their any base line settings that i can start out from besided where the carb is set at now. and the other thing i wonder is what are the screws that i need to be adjusting and tuning in. also does changing the jets to a different size make a difference.

[Captkaos]

If it is a basic Edelbrock 1406 start here:
http://www.edelbrock.com/automotive_new/misc/tech_center/install/1000/1406_manual.pdf

[hondarider188]

thank you capt. i think that the manual is exactly what i needed.

[hondarider188]

so one question i had when reading the manuel is that when i adjust the A/F mixture screws do they need to be turned in a sequence and adjusted the same amount. and the manual didnt talk really talk about how to adjust a manual choke. thanks