carb vs fuel economy on 200

[Timnmelinda]

changed carbs last weet went with 1100
the car is running really well went manual choke it is starting right up which it never had,it was always fussy and hard to start. It is now running strong compared to the holley 1 barrel that was on it, smoother than ever and maybe a little stronger, definatley peppier.
but the car seems to be thirstier it seems to be not getting as good of gas mileage. I do not think it is from the fact it is peppier feeling, trying to keep driving styles the same. In fact I think it is taking a little less gas pedal to cruise at equal speeds.

Is this normal? From all I have read on here it should be fairly economical with 1100 Other than carb it is stock except DUI, Headers, 2 inch dual exhausts with turbo mufflers and crossover. Should it be thirstier with the 1100 (Know I do not know what number the holley carb was top of my head and the old carb is on shelf in garage 20 miles away)

Tim

 

[Bort62]

Well, it's really hard to say w/o better data. "it seems to be thirstier" isn't really very quantitative.

It's entirely possible that you are running richer with the new carb.

 

[ASMART]

Itis probably runing richer. The fact that you can start it without any choke would tend to verify that.

 

[CZLN6]

Howdy Tim:

Is this a rebuilt carb? Where did you get it? Have you checked for gas leaks? They are hard to spot because gas evaporated so quickly. Fairly easy to smell. Given your mods a richer carb setting was likely needed to take advantage of your changes.

Have you tuned it at all?

The easy stuff- Start by reducing the idle to lowest possible setting with car in gear (Brake on). Next tune the low speed air screw. With the engine off slowly turn the screw all the way in, carefully counting turns. Write down and save. Put the screw back to that setting. Now start the engine. Let it warm up completely. Now slowly turn the screw in and out to the highest rpm, smoothest idle. IF it raises the idle speed of the engine, adjust it to lowest in gear idle setting.

Now, check the initial advance setting. It should be 12 - 16 degrees advance.

Now inspect the accelerator pump side of the carb. The accelerator pump arm is actuated by a pivoting arm. The fulcrum of the arm has two setting determined by the location of a roll pin. I can't lay my hands on my manual (Wife is remodeling) but the two settings are labeled "H" and "L" so I can't tell you which is which. One setting will lessen the amount of fuel squirted into the carb on acceleration. The other will increase fuel. IIRC you want the "H" setting for economy.

The next assessments involve removing the top of the carb. What is the float height set at? Too high a level will cause poor fuel economy because of siphoning.

What is the number on the main jet? Too large of a main jet will richen WOT and steady highway cruising. If you still have the take-off Holley you might want to check that jet for comparison. While Holley jets are not interchangeable I do think the jet numbers are comparable.

It would also help if you were to describe your typically driving situation.
Is it mostly in town? Highway?

Stay in touch.

Adios, David