Weber carburetor & fuel pressure question.

1crosscut

1crosscut

Well-known member
I'm starting to work on a car for a club member that has a Weber two barrel carburetor. It has a Holley inline fuel pump that from what I can find operates between 1.5 psi and 4 psi.
Is this range of pressure okay for the carburetor or would putting a pressure regulator be necessary?
The car isn't wanting to run well at low rpms.
While taking off the carb and manifolds I found some pooling of fuel in the bottom of the two intake ports that is concerning.
I also found that all four of the exhaust ports have equal signs of exhaust gases leaking at the bottom of each port.
I will be checking the flatness of the manifold surfaces.
 
My weber runs fine at 3.0 PSI. I use an Edelbrock pump. I would think that 1.5 to 4.0 would be fine. Do you have a fuel pressure gauge? If not, you might want to install one.
 
First fix any intake and exhaust leaks. Use the copper clad gaskets on the manifold. Re toque the nuts after the initial run and then at about 100 miles.

If you still are not getting a good response from the Weber, purchase some larger idle and main jets to try and get a new float valve. The float valve with the smaller hole works just as well for the Model A and has less tendency to leak. Use a larger main jet on the secondary throat because this throat is used for power. Use the minimum main jet that will provide good running on the primary throat because this will lead to better fuel mileage. Adjusting the idle a tad rich will help with the lower rpm.

That pressure range for the fuel pump is just fine for the Weber.

In hot weather the carburetor will boil out some fuel when it is parked after a drive. The hand throttle should be used to open it up a bit before starting and the choke should not be used. Do not use the foot throttle as this can pump more gas into the intake because of the acceleration pump.
 
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Thanks for the confirmation that the fuel pump has the right pressure range.

Found the problem with the even exhaust leak across the bottom of all four exhaust ports. The upper bolt for the oil return pipe was contacting the backside of the exhaust manifold tipping it out slightly not allowing good contact with the block.

I've ordered the gaskets and diaphragms for a rebuild of the carburetor.
 
It took me several tries to get the right jetting for my Weber. But once it was correct the carburetor is a real honey. The jets have the hole size in tenths of a mm stamped on them. It takes a magnifying glass to read them. It is a good idea to check the hole diameter with a set of small drill bits. Insert the shank of the bit that just fits in the jet and then mike the shank to read the diameter. Maybe the stamped size is in hundredths of a millimeter, I forget.
 
nkaminar said:
It took me several tries to get the right jetting for my Weber. But once it was correct the carburetor is a real honey. The jets have the hole size in tenths of a mm stamped on them. It takes a magnifying glass to read them. It is a good idea to check the hole diameter with a set of small drill bits. Insert the shank of the bit that just fits in the jet and then mike the shank to read the diameter. Maybe the stamped size is in hundredths of a millimeter, I forget.
Click to expand...

So how does your A run? What internal engine improvements?
 
Burtz block, cam, head, flywheel, overdrive. Runs great. I accidentally got it up to 73 one time and it still had more to go. Good tires, brakes, steering to match. I try to keep it between 60 and 65 on the interstate but like to drive it at 45 to 55 on back roads.

"Took my foot off the gas, and man alive, I shoved it down into overdrive."

https://www.youtube.com/watch?v=868DSi85odQ
 
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