Can you lean a Quadrajet carb?

[thesixs]

Is it possible to lean out a quadrajet carb for better fuel mileage? How would I do it?

[silicon212]

You don't. Not for better economy.

The only way you'll get better economy (without increasing emissions) is if it was too rich to begin with.

This is generally not the case. If you're after better economy, the best place to start would be a good tuneup using the manufacturer's specs as a baseline.

[MrPbody]

Cliff's High Performance in Mt. Vernon, Ohio, has a book specific to tuning Q-Jets. It is current and accurate.

As silicon212 says, Q-Jets are usually spot-on, but if it's not original to the vehicle or there have been changes made to either the carb or the engine, it CAN be optimized. Changing primary jets and metering rods, vacuum springs and float settings can all have an affect on fuel consumption. Be careful not to go TOO FAR. "Lean is mean, but fat's where it's at!" A too-lean condition WILL damage internal engine parts.

Jim

[bobss396]

I'm totally old school with q-jets. I use them right out of the box, I go for a quality rebuild or new ones and don't mess with them.

I set mine up with the tried 'n true crank in the mixture screws (gently!) until they bottom out, crank them out 1.5 turns. Then I'll hook up a vacuum gage, get it running and fine tune them at idle until I get the maximum gage reading.

Bob

[j cAT]

Originally Posted by thesixs

Is it possible to lean out a quadrajet carb for better fuel mileage? How would I do it?

this is not recommended....engine will be running too hot in the combustion chambers...

what will help to improve MPG is to increase the height of the carb over the intake manifold this greater distance will better allow the gas vapors to be injested by the engine with greater air evenly mixed ..

If you live in a hot climate this will also stop vapor lock....carb stays cooler..


limitation to this is the hood ...

[MrPbody]

What jCat says is only partially true. The engine MIGHT make more power if there is a spacer installed. However, economy will not improve, as the Q-Jet relies on mixture velocity to make maximum efficiency at lower engine speeds. Unless your spacer has the same flange as the intake (four individual holes, one for each "barrel", and the same size as the holes in the intake), that advantage will be lost. What "works" for a perfoemance application does not always work for an "economy" application.

Jim