This question is generally speaking for any engine with a carburetor experiencing hot restart problems.The flooding problem, engine cranks,stutters,blows out black smoke then clears. This problem is noticeable on engine compartments with a low hood . The issue is fuel vapor pressure supposedly.Modern gasoline will boil in the fuel bowl and then some how get the fuel gets into the carburetor bore and floods the engine. Is the fuel evaporating in the bowl and then escaping through the main discharge in the venturi and condensing.? Or is the heat expanding the fuel in the bowl ,raising the level enough to discharge into the venturi? To be clear this isn't a carburetor float,fuel pressure or ignition problem.
I never gave that much thought but have had starting issues with my ot truck (a real late model 71) that starts at the push of the ****on on a cold day but wants a tender touch on the throttle on very hot days after being driven a few miles. I guess a guy could run his car for a few miles to get it good and hot and then set a small container with a measured amount of gas in it next to the carb on the manifold, leave it for the same period that he usually leaves the car and go back and see if the gas level has risen or if the gas has evaporated. It might even be an interesting science project for one's kid that needs a project for physical science in school to write a paper on.
checked out the cool carb thing. seems pretty straight forward, and a lot of great reviews. seems incredibly simple to make one as well. my apache was having issues last year around this time with hot restarts. cool idea
I'm already a step ahead with a heat shield I made recently.The carb sits on an 1/4 inch phenolic insulator,then the shield,then a about an 1/8 inch gasket.It helps a bit..... The engine runs at 170 degrees,heat riser is open.I cracked the fuel line to relieve pressure immediately after shut down to eliminate any fuel pushing past the needle... The hood clearance is tight on these vehicles. Ya,off topic vehicle,but it's vintage stuff,with a common vintage problem.............. See that Carter W/O carburetor,it has no typical bowl vent like every other carb I seen has. Just wondering if a vent will help
Google popular science nov 1966. On page 16 in the "Say Smokey" column there's an explanation of one of the mechanisms, and some suggestions for cures allegedly by Smokey himself.
I fight that problem with my Flathead powered Tub, it has an electric pump, I try to turn the pump off about 20 seconds before shutting off the engine, lowering the fuel level in the bowls. Do you think the alcohol in the gas is a factor ?
My guess would be fuel expansion in the bowl compounded by pressure in the fuel line between the carb and the pump. I have pulled the line off of an engine that hadn't been running for an hour and got sprayed by fuel.
The heat will do several things and the problem is multi factorial. First the heat will expand the fuel in the line , that increases fuel pressure of the stagnant fuel between the pump and the seat. That can over power the needle/seat valve and flood the carb. Now the hot flooded carb evaporation and fuel level rising has even more fuel to work with if the above is happening. That raw fuel spillage into the manifold creates a vapor rich environment that will be exactly the opposite of what the hot engine needs. These types of fuel filters were used to help eliminate part of the problem, http://www.jalopyjournal.com/forum/showthread.php?t=726747 and keep cool fuel instead of super heated fuel at the carb.
The style fuel filter 31Vicky linked helps quite a bit, I had to do this to an OT car recently as it would not even start hot is was flooding so bad. Still have a little trouble, will be trying the phenolic spacer next.
Yes,I thought I had eliminated that.....but being I have the IQ of the average a tomcat ................ So...came home after a good ride,then a few minutes later I cracked to line to vent the fuel.closed the hood.It's sitting out in the sun,about 80F today.1/2 hour later it starts just fine...... So reading what you say and the guy above mentioned the old Yunick article....I was wondering why I didn't insulate the fuel line...So I did it. Heated up the engine again and waiting for the result
Insulating the line seems to have done the trick.After sitting for 40 minutes the engine started up fast and clean..I think it was a combination of fixes,the heat plate and the line insulation...
happens to me in the summer, and around here they say the oxygenated fuel is only used in the winter. So....no, I don't think that's the problem. I think the basic problem has to do with fuel being blended for use in fuel injected cars, not carbureted cars...it's too volatile for our hot rods. Happens to me on the 55 when I park for a little while, then it will run fine until I get on it a little bit, it will flood. The carbs and fuel lines near the blower get subject to a lot of heat. I'm thinking of redoing the fuel system with a return type regulator. And maybe raising the carbs on phenolic spacers, and possibly adding a heat shield below the carbs to block hot air from underhood from going up around the carbs. But this is all in the mental idea stage, no firm plans yet.
I have a Carter WD-O on my 49 Packard. In the manual it says for hot starts to hold the gas to the floor when starting.
Don't have to....waited about 20 minutes and this time it was flooded.A Fail! Gotta be heat fuel expansion in the bowl running over.... Oh well,in a few weeks hot temperatures won't be an issue and will have all winter to figure something to fix it......
If it was easy OR cheap to have cool-a$$ old rides then you wouldn't see so many lame *******s stuck in Honda Minivans! You will figure it out. Did anyone mention drilling the smallest (I mean like dental work small) possible hole in the top of the float bowl?
Almost every carb I've ever seen is already vented. Holding the accelerator to the floor should force the choke open and clear the manifold of excess fuel vapors once the cranking starts. Its important to hold it and not keep pushing it down.
Its the short stops that cause trouble. What's the float levels in the carb? Usually there'd be some room at the top before it starts spilling over. 100% positive the levels will rise but enough to spill over is quite a bit. What's the volume of the float bowl, expansion would be seen in a percentage of that volume and calculation could be made. I really think the majority of the problem is the fuel in the line increasing in pressure as it heat soaks. The volume of fuel in the line is probably equal to the bowl and subject to the same expansion percentage. That should be really easy to test and it should be easy to see if the carb is spilling over just look down the throat and watch it. Kind of like watching paint dry but thats how solutions are discovered. Quick test would be to shut car off, crack fuel line to releave pressure, wait 5 mins, tighten fuel line and start it up. See if the problem is still there.
Back in the 60s Chevy had problems on there Inline 6s with fuel expanding in the fuel line from the pump to the carb after hot shutdown. There fix was to drill a hole with a #80 bit between the chambers of the pump. Letting the fuel go back to the tank but now you can't take most pumps apart.
had this flooding issue on hot days recently with a 37 Chev coupe with a 350 sbc and a Edelbrock 4bblcarb/manual pump. Called Dennis at Cool Carb in Pa. and got a insulator from him which has solved the problem completely. Have over 2100 miles on the car now all driven this summer on mostly hot days and not one problem FWIW.
I did crack the fuel line test and the engine started ok......That's whay I insulated the fuel line.The float level is 3/8.I dropped it to 7/16 with no big improvement. Carter WO has no bowl vent to speak of...just a slight gap where the metering rod and accelerator pump rod goes through the bowl cover.Seems like a ****ty design..So I gave it a small vent tube,a bit hard to see in the photo....damn I have to hook up the hand throttle cable.. I took the carburetor apart one more time to look for defects.I changed the float needle set up to a different design .Now it looks like the float will apply pressure at a "better" angle to the float needle.All the neddles have Viton tips and fit properly in br*** seat.The parts are USA made if that matters. And the engine run at 170 degrees according to the Autometer mechanical gauge.
Took the top of the carburertor off and the fuel was boiling it's the ,alcohol in the gas that is causing all the problems if u can find a station that sells straight gas will sure help your problem
You said you let it set for 30 mins with the fuel line test. Its usually the short stops that cause this. .5 - 10 min. 30 mins is long enough to have let the spillover fuel evaporate out of the manifold.
Gasoline manufacturers say they formulate fuel to boil at the same temp be it pure gasoline or E10...Who knows??? For the record,some local stations sell 100 percent gasoline,usually 91 octane.I tried it,really noticed no difference............... The little 60 HP turd runs so nice,but when she's bad,she's real bad.............
I have the same issue, with my 305, in my Malibu. For the longest time, I didn't know why it happened. I did know, it was very annoying!! Gonna try the coolcarb thing. Hope it solves this problem.
It's the sorry ***, overpriced gas that they are selling now days boiling. I've got 3 different cars that are doing it, and one of them is a 79 Jeep Cherokee that has that fuel filter with the byp*** mentioned earlier in the thread. I could hear the carburetor bubbling after being parked for a few minutes. Not only does the Cherokee have the byp*** fuel filter but it also has a factory phenolic heat isolator under the carburetor. I wonder if Sta-Bil or something similar additive will raise the boiling point? Constant hot start flooding is really not good for the engine either.
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