QuestionSounds good. I'll check her out. I know Quadrajets are notorious for leaking through the well plugs but didn't know if my 2-bbl Rochester suffered from the same affliction.
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Thanks Dick--
My hunch was also flooding. What are your thoughts on possible vapor lock?
--Mark
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Dick--
First of all, thanks for your helpful answers in the past.
'68 Cutlass 350 with rebuilt 2-bbl carb. Runs very well but starts hard when warm and sitting for 20 minutes or more. Starts great within 5 minutes of shutdown when warm.
I thought the carb. rebuild might take care of it but it has not. Only way to start it is to push the gas to the floor when cranking as if it was flooded. Then it runs rough for a minute or so from the flood. Is my fuel boiling off or is the carb leaking?
I set the choke one morning and manually kicked the throttle under the hood and saw gas squirt so I don't believe the entire carb is leaking dry.
Ignition timing perhaps?
Not very impressive when I come out of a store and have people watching me to see what the car sounds like!!! Ha.
Thanks,
Mark
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Your symptoms are those of a leaking carburetor, flooding the intake manifold with gas. The fact that the accelerator pump chamber still has gas in it doesn't mean that the main bowl is still full. My guess is that there is leakage inside the carburetor, drowning the engine until you crank through enough air to blow it clear so the mixture can get back to normal. To prove this, run the car until it is thoroughly warm, then shut it down and quickly remove the carburetor from the intake manifold without tipping if over, so that it does not spill any gas, then set it on a clean dry paper towel on your workbench. Come back in an hour or so, I'm betting you will see and smell gas on the towel.
Another way to prove this to yourself is to let the car sit for an hour or so after you turn it off, then open the hood, lift off the air cleaner, and smell down into the carburetor - I'm betting you will smell gas down there, and maybe even see liquid gas on the throttle blades.
Carburetors which have been through the rebuilding process often develop this problem, as the cleaning chemicals remove the sealing coating from the porous aluminum and pot metal parts. The only cure is to replace the carburetor with a new (NOT REBUILT!) carburetor. NAPA, PAW, SUMMIT and other vendors can supply a new carburetor for your car - my advice is to spend the money to fix the problem once and for all - just buy a new carburetor and be done with it.
Try the paper towel trick first, if you want to be sure you are fixing the right problem.
Dick
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Vapor lock produces different symptoms. The typical vapor lock situation is when a car has been driven enough to get it thoroughly warmed up, usually on a hot day, then parked for a short while (to get the underhood temps high enough to get the fuel boiling), then restarted and driven about a block - at which point it begins to balk and lose power. It may continue to idle, but won't take any accelerator at all, in fact if you jam it to the floor, it will usually stall, and THEN be hard to start. But the initial restart goes normally, because the gas in the accelerator pump well is still there, so the engine will fire right up, and the car will drive normally until the gas in the float bowl is used up, then the vapor lock situation causes the fuel pump to be unable to pump fuel to refill the carburetor, and the engine starves for lack of fuel.
Cars that are vulnerable to vapor lock often show hesitation on long, high speed hill climbs in hot weather, or in a parade situation where the fuel lines can get really hot.
You described the symptoms of a fuel seepage down into the intake manifold perfectly - I think that is what you have going on there. You should be able to smell gasoline in your garage if you pull the car in hot and close the door to the garage, then come back and sniff in a half hour or so.
Dick
AnswerAll carburetors are made with somewhat porous materials, mostly "pot metal" but also the grade of Aluminum some of them use, but the surfaces are coated with some sort of gas resistant stuff when the carbs are new. The carb rebuilders use a very aggressive dip solution to clean them out thoroughly, and the consequence is that after a carb has been rebuilt once, it's probably OK, (unless they went to lunch and left it in the dip too long), but after twice, or maybe 3 times, it is going to start having the problems you describe exactly. I have a bunch of Packards and Chryslers which use WCFBs and AFBs - and I've been through this problem many times. The final cure is to pay the man and get a new carburetor - you'll be amazed at the improvement. By the way, if you come across a 4 bbl setup for your car, you might consider doing that to it. I did it to my 67 Pontiac 389, which came with the 2 bbl Rochester -and I was amazed at the improvement in both driving pleasure AND fuel economy! (I found a 67 GTO in the wrecking yard and just transferred everything). I usually try to talk people out of any sort of mods, but in this special case, and where there was an optional better carburetor, I make an exception.
Dick
