DEALING WITH ETHANOL IN YOUR GASOLINE
Ethanol, which comprises up to ten percent of each gallon of "normal" gasoline, has been causing problems for
motorists --- especially old car owners -- for years. Because it produces less energy by volume than "pure"
gasoline fuel economy is reduced (3+ fewer MPG reported), engine wear is accelerated and under-hood temperatures
are increased as the engine struggles to accomplish the same amount of work with less efficiency. This
sometimes causes vapor lock and/or heat soak in carbureted engines since the "gasohol" mixture also boils at a
lower temperature than gasoline --- a vicious cycle.
Organically-based ethanol is difficult to mix (and to keep mixed) with petroleum-based gasoline. These two
dissimilar chemicals have a tendency to separate, especially when in the presence of moisture --- even tiny
amounts of it. When this happens, the ethanol and water (both heavier than gasoline) sink to the bottom of the
fuel tank and render your vehicle inoperative.
Another problem with ethanol is that it is extremely harmful to buna (organic) rubber components in the fuel
system and will deteriorate them quite rapidly; wherever possible only synthetic elastics should be used.
Below you will find some suggestions to help you mitigate these problems.
• Visit pure-gas.org. This site may be able to direct you to a station which still sells ethanol-free gas.
"Trust but Verify": This is a user-driven website, so call the station just to be certain that they
have it. Because the farmers lobbied for exemption for their agricultural equipment to be written into the
ethanol mandate, ethanol-free gas can still be found at some stations . . . particularly in rural areas. All
Quality Plus Gas House stations in our area carry 93 octane ethanol-free gasoline.
• Replace all rubber hoses (no matter how old or how new) in the fuel delivery system of your carbureted
vehicle with Gates Barricade Carburetion Hose. For fuel-injected vehicles, use Barricade Fuel Injection Hose.
It has a synthetic fluoro-elastomer liner and multiple layers of other synthetic material to avoid
gasoline permeation and subsequent deterioration.
• Use products such as Bell Performance Ethanol Defense which extends the short "tank life" of modern
gasoline while it works aggressively to keep the ethanol form separating from the gasoline.
• Ensure that replacement rebuilt carburetors and fuel pumps (mechanical OR electric) are built to handle
ethanol. Rotary electric pumps seem to hold-up better than diaphragm-pulse electric pumps. Fuel
injection units seem to be holding their own . . for now. If you rebuild your own fuel systems components DO NOT
use "new old stock" kits, only newly-manufactured parts.
Questions? Contact Jeff Dreibus
The Old Carb Doctor
1127 Drucilla Church Road, Nebo, NC 28761
Special Info for Updraft Carburetor Owners
Your updraft carburetor has a unique characteristic of which you should be aware.
When you stop your engine, it is still drawing fuel vapor upward into the intake system until it turns its last
revolution. Once the engine finally stops, the suspended fuel vapor condenses into liquid and drops down to
the lowest point in the carburetor, which is typically the air intake just beyond the choke valve.
When this happens, the condensed gasoline has nowhere to go except out of the air intake, so it makes a mess. I'm sorry, but this is physics --- I can't
Some updraft carburetors have a hole drilled into the bottom of the throat so the gasoline can drip out of it instead. Many of them are threaded with 1/8"
female pipe thread. Never install a plug into this hole! It is there for the condensed fuel to escape through. If fuel remains in the carburetor
intake and the engine should backfire upon restarting (a common problem with early cars), then the fuel could ignite and start an engine
Instead, install a 1/8" brass male pipe thread fitting with a 1/4" compression nut and ferrule on the other end, then bend and install a 1/4" copper line to
direct the fuel away from the chassis and/or exhaust of the car. Do not bend the pipe after you install it; you could easily break the carburetor
casting if it is made of pot metal.
Also, don't tighten the fitting too tightly into the 1/8" pot metal threads; they can easily strip, or the casting can break. Instead, use some Permatex
High Performance Thread Sealant (Permatex #51521) on the male threads and tighten gently.
Questions? Please call 800-945-2272 and speak to Jeff.
Thanks for choosing The Old Carb Doctor for your professional carburetor restoration. Your carburetor should now function well, and hopefully you are
pleased with its appearance. To avoid any complications or disappointments, here are some installation tips. Not all instructions will apply to all carbs,
so just ignore those which don’t pertain to yours.
First, shake the carburetor gently to be certain that the float(s) can be heard to move. This is particularly important if the restored carb has been
stored for a long period prior to installation.
Before placing the carburetor on the intake manifold, check the mounting surface to be certain that all old gasket material has been removed and that the
surface is perfectly smooth. One or more mounting gaskets has been supplied with most carbs, and you should be sure to choose the correct one(s) for your
application. PLEASE note how they are wired onto the carburetor and be certain to install them in that same relationship.
Once mounted, be certain that the throttle linkage moves the throttle lever from completely closed to completely open without binding. Also be certain that
the throttle return spring is not rusted, distorted, too long or too short. If it is, obtain a new throttle return spring. Adjust the automatic
transmission throttle linkage and manifold-mounted choke to factory specs, if so equipped.
Install the vacuum lines. If they are rubber and are cracked or hard, replace them. Always use suitable clamps when installing power brake booster hoses.
Remember: Distributor advance and EGR valve circuits usually use spark-timed vacuum which increases with engine RPM; choke pull-off, thermactor,
transmission modulator, power brake and PCV circuits use manifold vacuum which decreases with engine RPM. Choke fresh air and bowl vent circuits install to
fittings located near the top of the carburetor with no vacuum present.
FUEL PIPE / FUEL HOSE WARNING: to reduce the possibility of fire use ONLY steel fuel pipe, never copper which can easily crack. Likewise, due to ethanol
and other additives blended into today’s fuels use ONLY Gates Barricade brand hose, never use 30R6, 30R7 or any other type of fuel hose. For those systems
which require the hose to be immersed in the fuel tank, use only SAE 30R10 hose. Clamp all hoses securely!
If fuel system has been open for any length of time, first purge any dirt from it which may contaminate the carburetor. With coil wire removed from the
distributor and securely grounded, use an extension hose and a suitable container (not glass) to catch the fuel as you crank the engine (or run the electric
pump) to flush out any debris in the system. Make all metal-to-metal fuel connections (not just those at the carburetor) with Permatex High Performance
Thread Sealant #56521or equivalent Teflon thread paste product used sparingly. Never use Teflon thread tape as it can shred-off and contaminate the fuel
Use only clean, fresh gasoline less than six months old because modern gasoline deteriorates very rapidly when stored in quantities as small as a vehicle’s
gas tank. If water, rust, dirt or old gas is present in the tank, it must be drained and cleaned prior to pumping gas to the carb. Ethanol Defense
additive should be used to stabilize new fuel and keep the gasoline and ethanol blended together.
Now re-attach your coil wire and start the engine. If the above procedures have been followed and the engine and fuel pump are otherwise in good repair,
the engine should start within 30 seconds of cranking (fuel bowl must fill first). Do not attempt to prime the carburetor as it is very dangerous and
unnecessary to do so if your engine is in good shape.
Allow the engine to warm-up, checking for gasoline and vacuum leaks as it does so. Correct any of these immediately.
With engine warm, make curb idle speed and mixture adjustments to the engine per manufacturer’s specs. In many cases, fast idle adjustment (if so equipped)
will already be made for you. If a correction does need to be made to the fast idle speed, do that the next time the vehicle is started cold and the choke
is not yet fully open.
Do not adjust air valves in secondary bores as these have already been adjusted for best drivability.
Install the air cleaner (when so equipped) and you are ready for a test-drive.
OUR WARRANTY: We warranty your carburetor restoration to be free of defects in materials and workmanship for a period of six months unless otherwise
specified. Failure to follow the above procedures voids this warranty and is limited in liability to repair, replacement or refund of the price of the
SPECIAL NOTES – PLEASE READ!
ETHANOL: what a nightmare! This stuff has caused all sorts of problems. Because it contains less energy than the gasoline with which it is mixed, the
engine must work harder to accomplish the same result. Working harder equals higher under-hood temperatures. Unfortunately, ethanol (hence the gasohol
blend) boils at a lower temperature than pure gasoline. Results: reduced fuel economy (typically 3 – 4 MPG) and more frequent occurrences of heat soak and
Heat soak occurs when heat rising from the engine saturates the carburetor and causes the gasohol to boil out (it boils at a lower temp, remember); much of
the gas boils into the carb throat. Now the engine is flooded and it won’t re-start until it cools down. It may also leave a mess on whatever is beneath
Vapor lock occurs when the engine heat becomes so extreme that the gasohol boils in the fuel pump or the fuel lines. The fuel vaporizes before it can reach
the carburetor, and the fuel pump simply can’t “pump through” this bubble of hot, vaporized fuel. Same result: the engine isn’t going to re-start until
THE OLD CARB DOCTOR CAN’T FIX HEAT SOAK AND VAPOR LOCK, NOR CAN WE SOLVE THE FUEL ECONOMY ISSUE! Therefore, these problems cannot be covered under our
warranty! Reducing engine temperature through various means and use of a regulated electric fuel pump may help, but no promises; I’m sorry.
Please don’t hesitate to call with questions regarding your carburetor.