How to Install a Carburetor Fuel Log Safely (Step-by-Step)

Quick answer

Install a carburetor fuel log by mounting the log to the carburetor inlet with new sealing washers, connecting the dual feed lines with the correct AN fittings, and tightening flare connections to a snug, leak-free fit. Pressure-test the system before starting the engine, then recheck every joint after the first heat cycle. Most leaks come from reused washers and over-tightened flare nuts, not from the log itself.

A carburetor fuel log is a simple part, but it sits between the fuel pump and two float bowls, so any mistake shows up as a leak, a fuel smell, or a stumble under load. This guide walks through a safe fuel log installation on a dual feed carb setup, from parts check to first start.

The process below assumes a typical V8 with a mechanical or electric pump and a dual feed carb. If your carb uses a single inlet, skip the dual feed steps and cap the unused port with a plug. Work with the battery disconnected and the fuel system depressurized.

Prep the fuel log and fittings before you touch the carb

Lay out the log, the two carburetor fuel line sections, and every fitting you plan to use. Check that the log threads are clean and that the inlet and outlet ports match your pump line size. If you are converting from a hard line, have new hose and the correct AN adapters on hand so you are not improvising mid-install.

Dry-fit the log to the carburetor inlet without washers first. It should seat flat against the bowl or inlet boss with no gap and no binding. If the log contacts the intake, a throttle bracket, or a vacuum line, change the clocking or add a 90-degree fitting before you tighten anything.

• Mistake to avoid: forcing a log that does not sit flat. That usually means the wrong inlet adapter or a bent mounting flange.
• Checkpoint: the log should rest on the inlet with light hand pressure only.

Mount the log with fresh sealing washers

Install new copper or aluminum sealing washers on both sides of the banjo or inlet fitting. Reusing crushed washers is the most common cause of a seep at the log. Thread the fitting in by hand until it seats, then snug it with a wrench while holding the log steady so you do not twist the line.

For a dual feed carb setup, orient the log so both outlet ports point toward their float bowls with equal line length. Unequal lines can make one bowl starve first under hard acceleration. Once the log is clocked correctly, tighten the mounting bolt or fitting to a firm snug, not a death grip.

• Mistake to avoid: overtightening the inlet fitting and crushing the washer. Snug plus a slight turn is enough.
• Checkpoint: the log should not rotate when you gently push on the outlet fittings.

Route and connect the carburetor fuel lines

Cut or select lines that reach each bowl with a gentle curve and no kinks. Keep the lines away from the exhaust, EGR tube, and any sharp bracket edges. If a line passes near a heat source, add a heat shield sleeve rather than wrapping it in tape.

Tighten each flare connection by hand first, then wrench it snug while holding the mating fitting with a second wrench. This prevents twisting the hose or the log. For hose ends, follow the manufacturer's assembly instructions for the specific hose type you are using.

• Mistake to avoid: letting a line rest on the intake or valve cover. Vibration will wear through it.
• Checkpoint: every line should have a small amount of slack and no contact with hot or moving parts.

Pressure-test and check for leaks

Reconnect the battery, disable ignition so the engine cannot start, and cycle the fuel pump a few times to pressurize the system. Watch each joint at the log, the bowl inlets, and the pump outlet. A dry paper towel held under a joint will show a weep that you might miss by eye.

If you find a leak, depressurize before tightening anything. Most seeps stop with a slight additional turn on the flare nut or a new sealing washer. Do not keep tightening a joint that has already been snugged hard; replace the washer or fitting instead.

• Mistake to avoid: skipping the pressure test and going straight to a first start. Fuel plus a hot engine is the wrong place to find a leak.
• Checkpoint: no fuel smell, no damp joints, and stable pressure after three pump cycles.

Torque the log and recheck after the first heat cycle

Once the system is dry, go back over the log mounting and line fittings with a wrench. Fuel log torque is usually a firm snug rather than a high number, so use the carburetor or log manufacturer's spec if one is provided. If no spec is given, tighten until the joint is seated and just firm, then stop.

Run the engine to operating temperature, let it cool completely, and recheck every joint. Heat cycles can relax sealing washers and flare connections slightly. This second check catches the small weep that only appears after the engine has been hot.

• Mistake to avoid: assuming the install is done after the first start. Re-torque after cooldown.
• Checkpoint: after cooldown, all fittings are dry and the log has not shifted.

Fuel log installation checklist

1. Dry-fit the log: Test the log on the carburetor inlet without washers and confirm it sits flat with no contact on the intake or brackets. If it does not sit flat, stop and fix the adapter or clocking before tightening.
2. Install new sealing washers: Use fresh copper or aluminum washers on both sides of the inlet fitting and snug the log by hand first. Reused washers are the most common source of a seep at the log.
3. Connect the dual feed lines: Route equal-length lines to each bowl with gentle curves, then tighten each flare while holding the mating fitting. Keep lines off hot and moving parts, and add a heat sleeve where needed.
4. Pressure-test before starting: Cycle the fuel pump with ignition disabled and check every joint with a dry paper towel. Fix any weep before the first start, not after.
5. Re-torque after the first heat cycle: Run the engine to temperature, let it cool, then recheck the log and all line fittings. Heat cycles relax washers and flares, so the second check matters.

Parts that make a fuel log install easier

• 90-Deg. 6AN to 5/16 in Bulkhead: The DeatschWerks 90-Degree Bulkhead Adapter connects a 6AN male flare to a 5/16 inch male barb in a right-angle configuration and includes a nut, finished in DW Titanium. A right-angle bulkhead adapter lets you route a carburetor fuel line cleanly through a panel or bracket without a tight bend that could kink the hose.
• 6 ft, 8AN Black Nylon Braided PTFE Hose: The DeatschWerks 8AN Black Nylon Braided PTFE Hose is a 6-foot length of black nylon braided PTFE hose. PTFE hose is a practical choice for fuel lines near heat, and a 6-foot length is usually enough for a dual feed carb setup with some slack to spare.

A safe fuel log installation comes down to a flat mount, fresh sealing washers, equal feed lines, and a pressure test before the first start. Take the extra ten minutes to recheck after cooldown, and the log will stay dry through the season.