Parts list for the D0PF-E 240 carb is 34A / Parts list for the D0PF-J 300 carb is 34C

Look thru the carb parts list in post #12 to see what parts are different. The carb kit is the same for all.

 

The two differences I saw were for (1) the Main Metering Jet and (2) the Fuel Inlet Valve & Seat Assy.

D0PF-E Carb kit 34A (for 240) Part Numbers
(1) "No 68 8MB 9533-A"
(2) "DOPZ 9564-C (CV-81)"

D0PF-J Carb kit 34C (for 300) Part Numbers
(1) "No 69 B7T 9533-A"
(2) "DOPZ 9564-B (CV-80)

Is there any way to find out what the difference is between these parts? Its possible that the 240 parts are smaller than the 300 parts, which may cause for fuel shortages under load?

James

 

It's possible you have the "wrong" carburetor installed, but it would take a serious mismatch to cause the problems you describe.

Smaller carburetors in a given engine CID actually tend to run better, not worse. It's all about the velocity of the airflow. A smaller venturi means higher velocity. So any given size engine and intake manifold combination "likes" a certain size CFM carburetor and in turn will atomize the fuel more efficiently. This means better idle quality, efficiency (MPG) low end torque, driveability and performance. It will have better snap on the throttle.

On the other hand, too small of a carburetor for a given engine will show itself by anemic power at the top end in particular, for example when trying to pass on the highway. It will not be able to "breathe". That's not to say however whatever carburetor you have installed is adjusted correctly. It may be seriously horked.

The good news is rebuild, setup and tuning documents, the manuals etc., are all available for free download to your smartphone or computer. YouTube videos will even walk you through the rebuild and tuning process. One thing to keep in mind though, oftentimes people are convinced it's a carburetor problem when it is not. The old saying goes "90 per cent of carburetor problems are ignition related."

 

I would take a multi-meter and test the coil since that is simple enough to do, and this identified a problem I ran into after rebuilding my carb (which was also necessary). I have the distributer converted to electronic ignition.

 

Just another thing to check, did you keep the same fuel cap when you changed the tank? I had what sounds like the same problem as you, removed the cap, and it ran great. put on a new cap, no more problems.

 

Appears member's have thoroughly addressed the issue, thought I would toss in couple additional suggestions. If decide to dip the carb suggest suggest remove floats; particularly if brass, or other plastic type material?

There are a number of 'how to' video's online, one important ingredient is establishing a clean work area. Once the body of the carb has soaked, one needs to clear the air/fuel passages, if there's no air compressor available, an aerosol can of compressed air, usually find them used in electronic equipment, should be a reasonable substitute? Have rebuilt Holley carb on couple occasions and till take pic's in event issue comes up during reassembly.