wcfb problem
Thread Starter
Burning Brakes
Joined: Oct 2005
Posts: 993
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From: Captain Cook Hawaii
wcfb problem
I have a base eng 63 vert w/pg. After warming up the eng will die when rapidly opening the accelerator pedal. Timing is set per Lars paper. Carb is freshly rebuilt. Accelerator pump is working and discharge nozzles are shooting fuel. Choke is fully open. Cold eng and no problem. Intake manifold has heat riser blocked. New gm fan clutch
Temp is between 170/180 indicated. Slowly advance the accelerator and it will accelerate ok. Any suggestions?
brgds
rene
Temp is between 170/180 indicated. Slowly advance the accelerator and it will accelerate ok. Any suggestions?
brgds
rene
Team Owner
Joined: Aug 2007
Posts: 58,061
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Army
I'd check the fuel filter first thing...next make sure your throttle linkage isn't loose anywhere. Next make sure your fuel pump is putting out enough pressure, say 4.5lb to 6.5lb. The lower end of this range is actually better for these old carbs. If all that's good you may have trash in your float bowls or something similar...
Also don't forget that there is a small bronze fuel filter WITHin these carbs right where the fuel line goes in...its worth checking that too..
Also don't forget that there is a small bronze fuel filter WITHin these carbs right where the fuel line goes in...its worth checking that too..
Race Director
Joined: Mar 2009
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From: Canada's capital
2020 Corvette of the Year Finalist (appearance mods)
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You need to check the fuel pump output to the carb. With the choke closed it may put out enough to perform because the mixture is richer, but with it open it might not put out enough volume. Just an idea and easy to check. I imagine you have a new fuel filter on. Good luck.
Le Mans Master
Joined: Feb 2008
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From: NJ Hockey beer league
If you are sure your timing is ok, and advance is working properly, I would suggest you check the float level in the carb. To do so, you would need to pull the airhorn (top) off, and check the floats per the 63 service manual WCFB section. It could be that the floats are set a bit too low and when you punch the throttle there is not enough gas in the bowl to meet the need. Sometimes even a rebuild that is done well can benefit from this type of field adjustment. 
Pilot Dan
Pilot Dan
Instructor
Joined: May 2006
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From: N. Tustin Ca
If all above recomendations checkout, try:
Do you have a rubber hose in fuel line to pump, If yes it may be soft when warm, restricting flow, or even a kink in the line from tank.
Get a cheap electic fuel pump and bypass mech/ one, but first guess would still be Carb.
Replace ignition coil and condenser (can act up when they get hot)
Do you have a rubber hose in fuel line to pump, If yes it may be soft when warm, restricting flow, or even a kink in the line from tank.
Get a cheap electic fuel pump and bypass mech/ one, but first guess would still be Carb.
Replace ignition coil and condenser (can act up when they get hot)
Le Mans Master
Joined: Sep 2008
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From: Lake Minnetonka, Mn
2018 C1 of Year Finalist
When was the last time this carb was rebuilt or opened up and looked at? If you need to check the float level, the primary float should be 5/32" and the secondary float should be 9/32". Some books will say to compromise and use 7/32 for both. Check and see how close you are.
Float drop should be 5/8' primary and 3/4' secondary. Measure drop from the bowl cover to the middle of the top of the float held in the upright position.
Float drop should be 5/8' primary and 3/4' secondary. Measure drop from the bowl cover to the middle of the top of the float held in the upright position.
Last edited by Dan Hampton; Jul 31, 2009 at 10:41 PM.
Thread Starter
Burning Brakes
Joined: Oct 2005
Posts: 993
Likes: 95
From: Captain Cook Hawaii
Art Gould rebuild on the fuel pump;instld last week and base re-indexed as per the latest pdf download posted a few weeks ago; [diaphram against the stop and base screws tightened.] I will check the fuel inlet filter this week end and then pop the airhorn off and double check the float level/drop. Dan; it was last year that I was in there and I am real carefull with my carb rebuilds. All rubber fuel hoses were done within the last month. This has been intermittent for over a year and I have a spare wcfb that was instld = no fix.
All ways use Chevron premium. Plot thickens, I Thank You Folks for your help. I will keep you posted!
brgds
rene
btw: got to stop this stop light embarassment!
All ways use Chevron premium. Plot thickens, I Thank You Folks for your help. I will keep you posted!
brgds
rene
btw: got to stop this stop light embarassment!
Team Owner
Joined: Aug 2007
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Army
Well, one other thing not to forget is that there has been a spate of fuel tank sending unit filter 'socks' breaking apart lately....putting trash in the fuel lines and/or restricting the tank 'draw'. Plasticman on the forum and some others have been fighting this problem...
Don't know if its the modern fuels or age but it could certainly restrict fuel flow on high demand.
Don't know if its the modern fuels or age but it could certainly restrict fuel flow on high demand.
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Le Mans Master
Joined: Feb 2008
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From: NJ Hockey beer league
Rene, one last thing to check on the carb before dismissing it would be to run the car and then remove the carb immediately afterwards being carefull not to spill any fuel out of the bowl. Pull the top, and do a VISUAL inspection of the fuel level in the bowl. You want to see it about 1/2 full with the floats out. Re check the float adjustments right after. Most of the kits contain a paper guage which does not align the floats laterally as the original Kent Moore guages do (pictured below) and they can stick. Check the alignment and see if any foreign matter is present (old fuel sock??) Also, there are significant differences between the many carb kits available today (which cover multiple years and have different gaskets that look similar) and what constituted an original GM kit when the manuals were written 40+ years ago. Be sure you used the correct gaskets for your year. Also, sometimes you need to tweek the settings to get the desired field result in the particular operating environment. 
Pilot Dan
Pilot Dan
Last edited by Pilot Dan; Aug 1, 2009 at 11:24 PM.
Team Owner
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Army
Since you swapped carbs and it didn't help I'd definitely focus on fuel delivery issues...
You say the problem happens when the car warms up which makes me think it does NOT happen when the car is cold with the choke on (thus running rich). Sure sounds like your carb is fuel starved on hard punches of the throttle.
You say the problem happens when the car warms up which makes me think it does NOT happen when the car is cold with the choke on (thus running rich). Sure sounds like your carb is fuel starved on hard punches of the throttle.
Instructor
Joined: May 2006
Posts: 211
Likes: 0
From: N. Tustin Ca
When it quits is there a backfire pop? or sputtering or just loss of power?
I have seen electrical quit on loading, Do you have electronic ignition upgrade on it,
or optical, magnetic replacement for points? If it's not fuel it could be:
points,wires, condenser,coil, rotor or dirt (arching under load), I've even seen Alternators
short out under load and heat.
I have seen electrical quit on loading, Do you have electronic ignition upgrade on it,
or optical, magnetic replacement for points? If it's not fuel it could be:
points,wires, condenser,coil, rotor or dirt (arching under load), I've even seen Alternators
short out under load and heat.
Thread Starter
Burning Brakes
Joined: Oct 2005
Posts: 993
Likes: 95
From: Captain Cook Hawaii
Thank you for all the input. Sorry I'm late; I had a 757 idg change here in Kona and logistics dragged the job on. I just ran up the 63 no problems. Pulled the fuel filter and a few slivers of metal probably from the prior fuel pump dropping a check valve. I let it warm up and no problem. I am going for a drive after I post this. A few other answers to your folks questions: No backfires or pops and I have the Lectric Limited one wire ign module set up. Yes Dan I did use the generic rebuild kit and yes on those paper float level gages but I also use a jobber drill bit for fine tuning. I will pull the air horn off after a run and the problem re-occurs. Frank; my choke is locked fully opened, but tend to agree on fuel delivery.
thx
rene
thx
rene
Instructor
Joined: May 2006
Posts: 211
Likes: 0
From: N. Tustin Ca
Rene, just wonderd if and what you found for problem, just like to know for the my own sake and it happens to me. One last simple thing, a weak battery can cause lower voltage to your ignition module, as it needs a little more current when accelerating.
Larry
Larry
Safety Car
Joined: Feb 2003
Posts: 4,068
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From: St. Joseph Mo
I have a base eng 63 vert w/pg. After warming up the eng will die when rapidly opening the accelerator pedal. Timing is set per Lars paper. Carb is freshly rebuilt. Accelerator pump is working and discharge nozzles are shooting fuel. Choke is fully open. Cold eng and no problem. Intake manifold has heat riser blocked. New gm fan clutch
Temp is between 170/180 indicated. Slowly advance the accelerator and it will accelerate ok. Any suggestions?
brgds
rene
Temp is between 170/180 indicated. Slowly advance the accelerator and it will accelerate ok. Any suggestions?
brgds
rene
Team Owner
Joined: Aug 2007
Posts: 58,061
Likes: 7,144
Army
I think he came back and said it didn't backfire...blocked off my riser on a dual quad WCFB setup and didn't change anything else...
Don't know when/who rebuilt the carb ... but on the WCFBs you have to soak the little leather cup on the accelerator pump in oil for a minute or two and then 'flare it out' before installation. If you do not the leather pump will not fill the pump cavity and will result in a reduced fuel shot.
Don't know when/who rebuilt the carb ... but on the WCFBs you have to soak the little leather cup on the accelerator pump in oil for a minute or two and then 'flare it out' before installation. If you do not the leather pump will not fill the pump cavity and will result in a reduced fuel shot.
Last edited by Frankie the Fink; Aug 5, 2009 at 09:17 AM.
Thread Starter
Burning Brakes
Joined: Oct 2005
Posts: 993
Likes: 95
From: Captain Cook Hawaii
I flare the pump leather during my rebuilds. I have a new filter on order. I blew out the sintered bronze filter that had some debris in it from a dropped check vlv in the previous fuel pump. It ran ok but I'm still not 100% convinced. I don't believe these filters can be effectively cleaned. If the filter went into bypass the debris would have to get through the needle vlv and into the bowls. Good point on the battery. I got to run it some more.
thx
rene
thx
rene
