Starting to get warm out around here. In prep for summer driving, a small primer on how to avoid fuel boiling in the carburetor on shut down. My "fuel percolation issues checklist"
I had this problem a lot in Southern GA. Part of the issue is me running whatever pump gas is available. Most of this is 10% Etoh junk. Sure sure people can say "well just buy pure gasoline." But I want my cars to be real street vehicles, I drive them everywhere. The only vehicles I own are carbureted, so it isn't an option to seek out special fuel, especially on 5-6 hour trips.
-Carb spacers. Edelbrock makes a 1/4inch spacer that is good. If you can go bigger, use the phenolic wood resin types, they are the best.
-exhaust crossover blocking. It isn't hard, just get some steel sheet jb welded in the exhaust crossover.
-Make a mini heat shield for the accelerator pump. If fuel in it expands it will push out the accelerator pump nozzle. I think in the 80's Ford addressed this issue by drilling a tiny tiny hole in the accelerator pump channel in the metering block which pushed the fuel back into the bowls. If you look at the location of the pump, it's pretty much a wide open heat sink on shut down. In my Galaxie, I run 2, 600cfm Holleys.... twice the fun! Would be just as bad with a double pumper.
-Keep your timing as far advanced as feasible. Limit mechanical to your max and push the initial a lil further if you can. I regularly run 18 initial and 38 total on a "stockish" engine, my HP engine runs 22 initial, 32total, and it helps keep it cooler.
-Fuel line insulation and isolation, keep it away from anything hot. Best is for it to enter the engine bay and go directly to the carburetor.
-Electric fuel pumps. Insulating the fuel lines doesn't matter if the fuel goes into an engine mounted fuel pump. Have you ever felt how hot the fuel pump gets while the engine is running? Hot oil is splashing on the inside.... just trust me, it gets hot. This also makes fuel routing easier as you can keep it away from anything hot. I run -8 SS braided hose and it stays decently warm through all scenarios.
-Fuel regulation and control. With modern fuels, the are designed for sealed fuel injection, so being exposed isn't an issue. Of course we run carbs, they are wide open. This fuel expands and contracts, and I do not have the data to back it up, but I think the specific gravity is different than it used to be. On side hung floats I regulate to 4.5psi With center hung floats I regulate to 5.5psi. I have also found that the .097 needle valves are better at keeping control than the .110 that most new carbs come with. Now some folks might say this isn't appropriate for performance usage. Everyone knows fuel in a carb is about flow not pressure. Use a larger pump and hoses than needed and have a good regulator.... no problems. I'm in the under 600hp crowd and the Carter HP 4600 works great as a lift pump, very quiet and seems very sturdy.
-Some folks suggest a return line. I have never used one, so I cannot comment. Thus far I haven't required one.
If you problem is only when shutting down in your garage, leave the electric fans running for a minute after shutdown or open the hood.
Anyway, this stuff has worked for me, and I run crap fuel and drive my vehicles freakin everywhere in 105 degree heat.
Starting to get warm out around here. In prep for summer driving, a small primer on how to avoid fuel boiling in the carburetor on shut down. My "fuel percolation issues checklist"
I had this problem a lot in Southern GA. Part of the issue is me running whatever pump gas is available. Most of this is 10% Etoh junk. Sure sure people can say "well just buy pure gasoline." But I want my cars to be real street vehicles, I drive them everywhere. The only vehicles I own are carbureted, so it isn't an option to seek out special fuel, especially on 5-6 hour trips.
-Carb spacers. Edelbrock makes a 1/4inch spacer that is good. If you can go bigger, use the phenolic wood resin types, they are the best.
-exhaust crossover blocking. It isn't hard, just get some steel sheet jb welded in the exhaust crossover.
-Make a mini heat shield for the accelerator pump. If fuel in it expands it will push out the accelerator pump nozzle. I think in the 80's Ford addressed this issue by drilling a tiny tiny hole in the accelerator pump channel in the metering block which pushed the fuel back into the bowls. If you look at the location of the pump, it's pretty much a wide open heat sink on shut down. In my Galaxie, I run 2, 600cfm Holleys.... twice the fun! Would be just as bad with a double pumper.
-Keep your timing as far advanced as feasible. Limit mechanical to your max and push the initial a lil further if you can. I regularly run 18 initial and 38 total on a "stockish" engine, my HP engine runs 22 initial, 32total, and it helps keep it cooler.
-Fuel line insulation and isolation, keep it away from anything hot. Best is for it to enter the engine bay and go directly to the carburetor.
-Electric fuel pumps. Insulating the fuel lines doesn't matter if the fuel goes into an engine mounted fuel pump. Have you ever felt how hot the fuel pump gets while the engine is running? Hot oil is splashing on the inside.... just trust me, it gets hot. This also makes fuel routing easier as you can keep it away from anything hot. I run -8 SS braided hose and it stays decently warm through all scenarios.
-Fuel regulation and control. With modern fuels, the are designed for sealed fuel injection, so being exposed isn't an issue. Of course we run carbs, they are wide open. This fuel expands and contracts, and I do not have the data to back it up, but I think the specific gravity is different than it used to be. On side hung floats I regulate to 4.5psi With center hung floats I regulate to 5.5psi. I have also found that the .097 needle valves are better at keeping control than the .110 that most new carbs come with. Now some folks might say this isn't appropriate for performance usage. Everyone knows fuel in a carb is about flow not pressure. Use a larger pump and hoses than needed and have a good regulator.... no problems. I'm in the under 600hp crowd and the Carter HP 4600 works great as a lift pump, very quiet and seems very sturdy.
-Some folks suggest a return line. I have never used one, so I cannot comment. Thus far I haven't required one.
If you problem is only when shutting down in your garage, leave the electric fans running for a minute after shutdown or open the hood.
Anyway, this stuff has worked for me, and I run crap fuel and drive my vehicles freakin everywhere in 105 degree heat.