MACH I Member
Joined: Nov 2006
Sounds to me that the engine is running short on available fuel in relation to the throttle opening. This could be caused by a clogged fuel filter, an extremely low and incorrect float level setting in the carb, a fuel pump with insufficient output, a partially clogged or restricted fuel line (An internally collapsed fuel hose, a dented or kinked steel fuel line or hose) and a clogged fuel inlet sock that is on the fuel level sender assembly in the tank.
I've found that a very fine granular form of rust will develop inside of an old fuel tank that has been sitting. This form of rust is like a powder and will suspend itself in the fuel. This rust will gather and clog the fuel line inlet filter, (Sock), until there is enough built up to cause fuel starvation. The finer rust will pass through the sock and start clogging the filter, further restricting flow.
The more time that the car is running, the worse the clog can get, as the fine granules accumulate. Sometimes the granules will stick to the filtering surface and sometimes they will fall off when the engine is shut down, only to reattach the next time the engine is run. This can cause an intermittant supply of fuel and a reoccuring engine performance problem. This may be why it takes a little time before the engine starts to act up.
Sometimes you can remove the tank and try to flush out most of the rust with mineral spirits, but usually the only real remedy is to replace the tank. I've been through the rust in the tank issue where I was continually replacing filters. I'd remove the filter and give the inlet end a couple of taps on the work bench only to find a small pile of mud like rust coming out. This left me wondering when this was going to stop. After all, for the price of about 10 filters, I could buy a new tank. If you were to figure in the cost for labor, it would be even fewer filters.