Culprit found?

61BISCAYNE

Well Known Member
Supporting Member 1
#1
I have been fighting some hot start / flooding problems over the last few years. You know...drive the car thirty miles or so, stop for gas, get a Coke, and get back in to start after ten minutes of heat-soak and the engine acts flooded. Hold gas pedal to floor and it starts, puffing a little black smoke. Never stranded me, just annoying. It seems the fuel mileage has been continually getting worse too.
So I hooked a fuel pressure gauge to the Biscayne Friday evening. My gauge reads 0 to 10 psi. Gauge pegged out at 10 psi plus. Don't know how high the pressure was?? Killed the engine and within a minute or two the pressure blead down to five psi and within ten minutes it lost all residual pressure down to zero, indicating either a bad check valve in pump and/or carb needles not closing. Bought a new pump at Napa Saturday morning rated at 5 to 7 psi. Installed pump with gauge. Started motor and gauge read 6.5 psi regardless of rpm. Killed motor and it held residual pressure at 5psi for two hours. Hoping this may solve some of the flooding issues. Thinking the ten plus psi was blowing past the float needles and flooding the engine. I have read that Edelbrock carbs don't like anything over six psi or they will flood. I haven't had a chance to test drive it yet, but I do have high hopes. What are your thoughts or predictions?
 

62impala409

 
Supporting Member 1
#3
I agree that 10# plus is way too much fuel pressure. I did some research in the GM heritage center documents and found that all of the SB Chevy motors and the '62 409 motors used the 5 1/4# to 6 1/2# fuel pump. All of the '63 and '64 409 motors used the 7 1/4# to 8 3/4# fuel pump because they were equipped with the fuel return line coming out of the fuel filter. That return line outlet on the fuel filter housing had an .080 orifice to lower the fuel pressure to the carb and circulate the fuel to prevent vapor lock. I am using the return line setup on my '62 motor to prevent pressure buildup in the fuel line after shutting down a hot motor. I still get some hot start issues if I use fuel with 10% alcohol. We are fortunate to have quite a few stations nearby that still sell non-originated fuel. Another big help for a clean start was to add the phenolic carb spacers. Leo
 

61BISCAYNE

Well Known Member
Supporting Member 1
#5
I installed a 1/2" thick phenolic spacer last summer and it did seem to help...a little. I would like to know more about the off road need and seat. How are they different from standard? Do they use the same float?
 

skipxt4

Well Seasoned Member
Supporting Member 14
#7
Leo: Will the off road, spring loaded needle's, work on original AFB carbs?:dunno I bought, a couple of Edelbrock floats, from Summit, a few years ago. After comparing them, side by side, to the originals, I noticed the Edelbrock floats were smaller, than the AFB floats. So, I sent them back. Didn't know if this would screw up the float height any. Thanks:)
 

62impala409

 
Supporting Member 1
#8
I have not compared original Carter afb parts with the Edelbrock parts. I do know that the later Carter and Edelbrock parts are interchangeable and they share overhaul kits. I believe Ronnie Russel is pretty familiar with these carbs. He may be sharing info soon. :dealLeo
 

GCAMINO

 
Supporting Member 1
#9
I too have had problems with the Edelbrock 4 barrel carbs, same as 61 bis. I have also heard complaints from others with the same problem. Interesting to hear about the fuel pump pressure. I never checked mine. Sold the car . The fellow I sold the car to changed to a Holley, problem solved.
 

61BISCAYNE

Well Known Member
Supporting Member 1
#10
I hope to drive the car some this weekend. The temperature is only supposed to be in the 50's, so that won't be much of a heat-soak test, but it would flood regardless of temp. I will give an update.
 
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