I have a 1977 Datsun 620 w/ a l20b and it is lacking power and doesnt accelerate like it should. It has always stumbled when give it gas, and recently I had an issue that required that the carburetor be replaced. It was the first time I had an issue where the truck didnt run and it had been sitting about 20 years before I bought it. The secondary on the carburetor was corroded shut and I was not able to fix it. I bought a weber conversion kit for it and the fuel system is not the cause for the current problem. I have also checked the spark plugs and the issue isn't there either. My dad thinks the problem might be that the timing is incorrect, could that be what is causing the problem?