Carb Capers

Keeping That Holley Carburetor In Shape

Bob Mehlhoff Aug 1, 2002 0 Comment(s)
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Hot rodding thrives on making and maintaining power. Whether the added power is supplied from a full-flowing exhaust system, better cylinder heads, or adding a better carb, the search for more performance never stops. To add that extra power, many performance enthusiasts choose proven Holley carburetors. They work great, are easy to install, and look cool when the hood is up. But as with any component, proper installation and maintenance are key to optimal performance. To help with that, we spent an afternoon with carburetor guru Ted Granger from Ted's Carburetor Service in Lancaster, California. Granger showed us the best, time-tested ways to get the most performance from your carburetor.

Ensuring that your carburetor operates properly requires routine inspections. After several thousand miles of use, check that the carburetor mounting nuts are tight. But be certain to never over-tighten anything. Warped baseplates from over-tightening can create vacuum leaks or cracks. Vacuum hoses should also be periodically inspected. The most common cause of poor driveability can be attributed to vacuum leaks.

After adding performance parts, many enthusiasts decide their carburetor needs to be jetted, but usually the factory jetting is right where it should be. If your carburetor is not performing as well as you think it should, consult a Holley repair manual and try the stock jetting. A properly jetted carburetor provides a crisp throttle and delivers better fuel economy.

Granger says that he often receives carburetors that are simply out of adjustment. Whether it's the electric choke or air/fuel mixture screws, many carburetors have been adjusted far from the factory settings. Returning these settings to factory specifications frequently makes the carburetor perform like new.

To repair Holley carburetors, Granger recommends using either a Holley rebuild kit and gaskets or a quality aftermarket kit. Inferior gaskets can cause driveability problems or fuel and vacuum leaks. It's also important to use the proper tools. Flare wrenches, correct-size screwdrivers, and a clean work space all contribute to a quality rebuild.

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Working on fuel lines requires special tools. Remember to use a tubing cutter--never cut a metal fuel line with a hacksaw. Ream out the cut, and add a flare appropriate for the application.

Because a flare fitting seals under compression, there is no need to apply thread sealer or Teflon tape to the tube's nut. Teflon tape can work lose and enter the carburetor's fuel system and clog passages.

When reinstalling the secondary diaphragm, be certain that the sealing-cork gasket is still in place. If it's not, the vacuum leak will not allow the secondary diaphragm to operate.

To prevent the screws from grabbing the rubber secondary diaphragm during assembly, add a few shots of WD-40 to each screw.

Is your carburetor giving you idle problems? If so, start with the basics. For most Holley carburetors, the air/fuel mixture screws should first be set to 1-1/2 turns outward before their final adjustment. Always adjust all idle mixture screws evenly.

To allow your distributor's vacuum-advance unit to operate properly, the hose should connect to a ported vacuum source and not direct vacuum. A good test for this is to remove the plug with the engine idling and check for vacuum. There should be none at idle.

When wiring the electric choke on a Holley carburetor, run a 12-volt source from a switched terminal. Never connect the choke to the positive side of the coil.

An air cleaner not only delivers clean, undisturbed air but also minimizes the chance of a fire spreading in your engine compartment. Also make sure that the air-cleaner lid does not block or interfere with the carburetor vents. If this happens, stalling can occur.

After installing the carburetor, check wide-open throttle (WOT) operation. For proper throttle return, install a return spring that is just strong enough to pull the throttle back. Too strong a return spring can cause unnecessary wear to the throttle shaft and bushings.

To remove a stubborn fuel bowl, tap it with a plastic mallet. Using a screwdriver to wedge the bowl away from the carburetor body could create a permanent leak.

Be careful during reassembly because over-tightening the carburetor can strip threads.

When checking accelerator-pump operation, remember there should be no clearance between the actuating-lever screw and the diaphragm lever at idle. When adjusted properly, the diaphragm lever should be able to move enough beyond WOT to accommodate a 0.015-0.020-inch feeler gauge as shown in the photo.

All gasket surfaces should be cleaned carefully with a wire brush to remove old material.

Use a wide-blade screwdriver or a jet-removal tool when replacing a jet. The wrong-sized screwdriver could damage the jet's orifice and affect the flow.

Work in a clean environment to prevent debris from entering the open carburetor, and remember to blow out all passages with air before reassembly.

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