OK guys, I have some symtoms and wanted to ask your opinion/s on what you think could be the problem.
I have a recently rebuilt 1976 Chevey 350 engine. It starts and runs great UNTIL it runs for 5 minutes or so. It begins to idle poorly. I noticed that the output pressure of the mechanical fuel pump drops from 7 PSI to 3.5 PSI after 5 minutes. I can rev the engine OK but the idle is poor. When I first start the engine, I can shift into reverse or drive, and it won't die. Once I have run it 5 minutes or so, when I shift it into reverse or drive it dies.
Now, I was thinking maybe a vacuum leak but how could that cause the fuel pressure to drop? I thought maybe a clogged fuel filter, but wouldn't the engine not rev?
Any ideas?
