Hi there, a German needs help: Own a 1968 DeVille Conv. 472.
When I drive the car it seems to me that there´s too less torque.
I built in a new fuelpump and new fuel filter. When I to operate the car
at full capacity (such as driving up a hill) it stutters and can only go on when I release the accelerator for a moment. This car should have be so much power, so what´s the problem?
Appreciate any help, thanks, Michael

Fuel pump has internal valve to send fuel back to tank for circulation. The valve opens when there is more fuel pressure than the carburetor needs. This keeps a supply of cool fuel to the carburetor. This valve can become clogged and remain open. If this happens, the carburetor will have a fixed, low volume of fuel. The car will idle and operate at low loads fine but will fault when asking for steady higher engine power.
The test is to block off the small fuel return hose from the pump to the tank.
this should only be done for a short time as a test. If this makes the car drive normally again then it is time to replace the pump and make sure there is no debris in the fuel tank. I had this exact problem long ago with a pump that was almost new. Auto parts can be trouble when new also.