Join Date: Dec 2005
Location: Kitchener, Ontario Canada
boiling due to heat from the EGR passage in the intake not being properly shielded is an issue but this doesn't sound like what's happening to you. When boiling happens, you would have definate performance issues and it would run poorly (if at all) when engine gets up to temperature. I'm speaking from personal experience.
My first thought was that you had a leaky carb (there's a quick test for this) but if you have let it sit full of fuel overnight, that's probably not it.
I have to ask how it performs otherwise...what are your hot starts like? Performance? does it run rich or lean, stumble, etc? If it is fine otherwise I would suggest starting procedure...we in today's world of computer controlled fuel injection often forget "how it was" with naturally aspirated engines...we can't expect them to fire up like modern technology when sitting a few days!
Your climate/humidity, etc. I can set a carb full of fuel on my bench in a pan with a piece of paper in the bottom of the pan. If any fuel leaks, it will stain the paper. I have found up to 3/4 of the float bowl can vanish into thin air in as little as 3 days sitting, with the float pretty much all the way down..from evaporation, not leaks. Because of carb venting etc, your carb is not a sealed unit. It is open to the air and gas evaporates quickly (hense the paper, drips could drop and dry up and never be seen...the paper is the proof nothing ever dripped). Depending on your climate this could take longer (or less time) in your carb.
Proper starting procedure is critical also (don't laugh, rochester's are fussy and if you don't treat them right, they become tempermental quickly).
On my '69 Impala with a 4MV, cold starting procedure per the owners manual is to depress pedal to floor one time and crank. The purpose of this is to set the manual choke - not to indtroduce fuel into the carb however you may get a small pump shot if there is enough fuel in the bowl. In my case the carb is set up 100% stock, and if I do ANYTHING else but this procedure it will flood, and either start and die, start and run very poorly, or crank forever before starting...and then running poorly. However if I follow this procedure it will start, go immediately to fast idle, warm up quickly and then it's off for great driving, wonderful performance and power. Having said all this, if my car sits for 3 or more days, it will crank for up to a full 6 or 78 seconds before it fires using this starting procedure...and this is 100% normal.