Fuel System

Progressive Weber Carburetor Set Up

It is important to follow all linkage and lever installation instructions.
The number one and two reasons for tuning errors are improper linkage installations and
over tightened linkage nut, causing a binding in linkage assembly.

CALIBRATIONS MAY VARY DUE TO REGIONAL FUELS AND STATE OF ENGINE TUNE AND PERFORMANCE. POOR RUNNING QUALITY DOES NOT MEAN A DEFECT IN THE CARBURETOR.
AN ADVANTAGE OF THE WEBER CARBURETOR IS ITS EASE OF ADJUSTMENT AND TUNING.

SET UP ADJUSTMENTS

Start set up by confirming carb base line settings.

Do not depend on the factory delivered settings. Check them before the carb is installed.
All settings are done with choke disengaged or warmed up so that the choke is fully opened and disengaged.

Parts you might need – link to category Performance Carburetor Kits

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IDF Carburetors Low Speed Circuit Tuning

It is most important to verify all linkage and levers are installed without binding
and the linkage opens to full throttle and is allowed to close to the Idle Speed Screw.
This is the number one and two reasons for tuning errors, improper linkage installations and over tightened linkage nut, causing binding in the linkage assembly.

The Individual Runner carbs, IDF, have individual Idle jets and mixture screws for each barrel.
They also have an additional air bleed screws and lock nuts. This is not used for idle adjustment or idle quality.

The settings for these screws should be closed.

Standard IDF Settings:

Parts you might need – link to category Performance Parts

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Carburetor Set Up and Adjustment 34 ICT

It is most important to verify all linkage and levers are installed without binding and the linkage opens to full throttle position and is allowed to close to the Idle Speed Screw.
This is the number one and two reasons for tuning errors, improper linkage installations and over tightened linkage nut, causing binding in the linkage assembly.

Parts you might need – link to category Stock Replacement Parts

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Parts you might need – link to category Stock Fuel Pumps

Parts you might need - link to category Carburetor Jets

Someone wrote with problems with the 34 PICT/3 carburetor on his 1600cc twin-port engine (new manifold boots and gaskets, new plugs and leads, 009 centrifugal-advance distributor). I have read lots on the common “flat spot” problem (stumbling at low-rpm acceleration) and have tried the adjustments, but I still have the flat spot. I have opened up carburetor and checked the float, needle valve and seat — all okay. I also cleaned and blew out all visible rubbish. The motor seems to idle okay, but it spits and coughs when accelerating. If I up the size of the main jet and idle jet by one size or two will this help?

Parts you might need - link to category Ignition System

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Parts you might need - link to category Stock Carb Replacement Parts

Checking for Vacuum Leaks

Leakage of air into the intake manifold can be an exasperating problem. This phenomenon occurs because the pressure inside the intake manifold is lower than atmospheric pressure. If there are any holes in the manifold or at any of the connection points, then air can be sucked into the manifold, causing the fuel-to-air mixture to become too lean.

Air being sucked into the intake manifold can cause -

The car acts like it’s not getting enough fuel; i.e., running too lean.

The car may run well at highway speeds, but the engine dies at idle and will only idle at higher than normal rpm (e.g., >1200 rpm).

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Trouble Shooting – Fuel system

Excessive fuel consumption

The air filter element is dirty or clogged.

The ignition timing is incorrectly set.

The emissions system is not functioning properly.

The carburetor/fuel injection internal parts are excessively worn or even damaged.

The tire pressure is low or the tire size is incorrect.
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