having [a problem] with fuel system.... Advice?
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Registered User
Joined: Jun 1999
Posts: 10
From: New Mexico
having [a problem] with fuel system.... Advice?
Hello Guys,
Below is an email laying out the problems dad is having with his 66 Vette. Thought maybe you all might know what were doing wrong. Any help would be appreciated as we have not experinced problems like this before. TIA,
Chad
78 Nova
540 BBC
ATI Procharger D-3M
Spearco Intercooled
Speed Pro sefi
email sent to Holley:
66 Vette 3200 lbs
4spd, 3.73’s
502 cid BBC
611.6 hp at 5500 rpm
645 ft tq at 4200
Sea Level dyno numbers
Elevation here is 5,500 ft
What we have:
Street Avenger Carburetor 870 CFM Vacuum Secondary
Holley Pro Series Black Pump, pre set 14 psi, free flow capacity 140 gph
Max Pressure Regulator adjustable from 4.5 – 9 psi
No Return Line
3/8 feed line
I have had many Holley carbs and large CI engines since 1964. I have had minimal problems getting them to run. It is now pay back time I assume…and how!
I have had nothing but hell with the current set up, to say nothing of the electric choke which is a secondary but equally confounding issue. The Edelbrock electric chokes have always been an easy proposition to tune.
Anyway, my set up is probably wrong but it was purchased from the after market catalogs without any reason to believe it wouldn’t work. I didn’t want to have to run a return line on the 66 Corvette back to the fuel tank. The 427 high performance L-72 ran fine with only a mechanical pump. The 502 does not have a casting port for a mechanical pump.
The car floods out of the primary bowl vent tube and even squirts or dribbles fuel out of the accelerator pump squirters with the car idling and no pedal. The fuel pressure at the dual feed is set at only 5 psi. The carb continues to pump out of the squirters for a time after the fuel pump and engine are both off.
I have gotten the car to run very well with light to moderate accelerator pedal. However, if you launch hard its all over...the car will actually die from the flooding out of the primary vent tube. I don’t like washing down the cylinder walls repeatedly while trying to correct this problem. I almost got run over last weekend when the car died while crossing a street!!!
I have an 850 double pumper and compared the float setting with the new 870…they are very different. The 870 is perhaps a quarter of an inch higher with the same amount of needle and seat threads showing above the float setting boss on the bowl. It also seemed that the float might actually be making contact with the flat plastic vent tube out of the metering block when the bowl level was correctly set. I machined the 870 bowl/needle-seat boss down and matched the 850…no change…it still floods out. These two carbs have the same bowl specifications and floats…what gives?
The bowl level is set just slightly below the sight plug as the instructions call for. I have also extended a fuel pressure gage from the dual feed line out to the windshield. The fuel pressure regulator stays constant under acceleration consistent with what it is set at at idle.
After the flood out the car need only run at idle for a few seconds and the fuel starts gushing out of the primary bowl vent tube. I changed the needle and seat and it made no difference.
Any suggestions on a possible cure would be appreciated.
Lynn Byers
Below is an email laying out the problems dad is having with his 66 Vette. Thought maybe you all might know what were doing wrong. Any help would be appreciated as we have not experinced problems like this before. TIA,
Chad
78 Nova
540 BBC
ATI Procharger D-3M
Spearco Intercooled
Speed Pro sefi
email sent to Holley:
66 Vette 3200 lbs
4spd, 3.73’s
502 cid BBC
611.6 hp at 5500 rpm
645 ft tq at 4200
Sea Level dyno numbers
Elevation here is 5,500 ft
What we have:
Street Avenger Carburetor 870 CFM Vacuum Secondary
Holley Pro Series Black Pump, pre set 14 psi, free flow capacity 140 gph
Max Pressure Regulator adjustable from 4.5 – 9 psi
No Return Line
3/8 feed line
I have had many Holley carbs and large CI engines since 1964. I have had minimal problems getting them to run. It is now pay back time I assume…and how!
I have had nothing but hell with the current set up, to say nothing of the electric choke which is a secondary but equally confounding issue. The Edelbrock electric chokes have always been an easy proposition to tune.
Anyway, my set up is probably wrong but it was purchased from the after market catalogs without any reason to believe it wouldn’t work. I didn’t want to have to run a return line on the 66 Corvette back to the fuel tank. The 427 high performance L-72 ran fine with only a mechanical pump. The 502 does not have a casting port for a mechanical pump.
The car floods out of the primary bowl vent tube and even squirts or dribbles fuel out of the accelerator pump squirters with the car idling and no pedal. The fuel pressure at the dual feed is set at only 5 psi. The carb continues to pump out of the squirters for a time after the fuel pump and engine are both off.
I have gotten the car to run very well with light to moderate accelerator pedal. However, if you launch hard its all over...the car will actually die from the flooding out of the primary vent tube. I don’t like washing down the cylinder walls repeatedly while trying to correct this problem. I almost got run over last weekend when the car died while crossing a street!!!
I have an 850 double pumper and compared the float setting with the new 870…they are very different. The 870 is perhaps a quarter of an inch higher with the same amount of needle and seat threads showing above the float setting boss on the bowl. It also seemed that the float might actually be making contact with the flat plastic vent tube out of the metering block when the bowl level was correctly set. I machined the 870 bowl/needle-seat boss down and matched the 850…no change…it still floods out. These two carbs have the same bowl specifications and floats…what gives?
The bowl level is set just slightly below the sight plug as the instructions call for. I have also extended a fuel pressure gage from the dual feed line out to the windshield. The fuel pressure regulator stays constant under acceleration consistent with what it is set at at idle.
After the flood out the car need only run at idle for a few seconds and the fuel starts gushing out of the primary bowl vent tube. I changed the needle and seat and it made no difference.
Any suggestions on a possible cure would be appreciated.
Lynn Byers
Last edited by Injuneer; Mar 24, 2003 at 06:26 AM.
Registered User
Joined: Jun 2002
Posts: 243
From: TN
http://www.quickfueltechnology.com
Give these people a call. If it has to do with holleys they have most likely seen it. Ask for Marvin or Marty.
Give these people a call. If it has to do with holleys they have most likely seen it. Ask for Marvin or Marty.
Registered User
Joined: Aug 1998
Posts: 520
From: Perryopolis, Pa
Chad,
Please clarify......
Is the float level creeping at idle or will it stay steady after an extended idle period?
Are you driving it with the air cleaner on when you have the flooding problem? Holleys will pull fuel from the vents sometimes when the air cleaner lid is too close to the vent tube.... try a brief run without filter.
What vacuum do you have at idle & what is the power valve setting? It should be approx 1.5" below the idle vacuum.
What is the idle speed?
Tell me some of this info & maybe I can help.... I routinely do mods on these carbs.
Please clarify......
Is the float level creeping at idle or will it stay steady after an extended idle period?
Are you driving it with the air cleaner on when you have the flooding problem? Holleys will pull fuel from the vents sometimes when the air cleaner lid is too close to the vent tube.... try a brief run without filter.
What vacuum do you have at idle & what is the power valve setting? It should be approx 1.5" below the idle vacuum.
What is the idle speed?
Tell me some of this info & maybe I can help.... I routinely do mods on these carbs.
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