I have a 1971 460. It has a Holley 750 vacuum secondary carb, new plugs (gaped properly), new wires, new coil, new cap, new rotor, new condenser, and fairly new points set correctly. Timing is set at 4d btdc. I can't figure out the problem. It runs for 30-45 minutes then dies. It will not restart for 12-14 hours. It runs perfectly until it dies. Every once and awhile it will run longer but never more than an hour. It does have black smoke coming out of the tail pipe at idle but its not very much. It turns blue when you gas it hard. It has 41,000 original miles. It is not in a truck. It's in a Lincoln Continental. I just don't know who else to ask. I'm just a garage mechanic. I'm not sure what the problem is. Any help would be great! I want to drive this car more than 30 minutes at a time.

 

I have noticed when it dies the starter has trouble turning over the engine. It's like the battery is dead. If you let it sit for an hour it will crank just fine again but won't start until the next day. I assume the starter is weak because it has other issues. The engine has good oil pressure. I am going to replace the distributor this week and see if that helps. If not I'm out of ideas.

 

Try replacing the ignition coil.

 

The timing should be set at around 10-12* after top dead center at idle with the vac hose plugged. Have you made sure it's getting fuel ?

 

According to the valve cover It's 4d btdc. I figured out the problem this morning. Vapor lock. The fuel is heating up because of how the lines are run.

 

I didn't figure out the problem after all I guess. I replaced the manual fuel pump with an electric one near the tank. I ran all new rubber lines bypassing the metal one near the front of the engine and the problem still remains. I have replaced everything to do with spark and fuel and I am out of ideas. Someone told me to replace the thermostat with one that opens at 160. He said that will make the engine run at about 180 185. He said that is below the boiling point of gasoline. That way it won't boil even if the carb heats up. I have a 1 inch aluminum spacer so I didn't think that could be the problem. Any thoughts? I'm tired of spending money. I just want to drive it!

 

You need to determine whether it's a fuel problem or a ignition problem when it quits. Have you looked at the plugs when it won't start ?

 

When it dies, try to restart it with a little starting fluid. If it fires up, then you know you are not getting fuel. If it doesn't, then spark is your problem.

 

It will start back up with a little gas poured in the carb.

 

I am getting spark but no fuel when it won't start. I am still assuming its vapor lock. There is no way the pump is not pumping enough fuel to the carb. There is also no way that my brand new Holley carb is screwing up. I think once the gas makes it to the fuel bowls that's when it starts boiling. I think I am going to try replacing the thermostat with a 160 and see if that helps. I have spent so much money on this engine and it is still doing the same thing it was when I bought the car.

 

Don't waste your time on changing the thermostat - it won't help much if any and you don't want to run your engine that cold for other reasons (poor efficiency, increased cylinder wall wear, etc).

One possibility to check: the rubber hose on the suction side of your fuel pump, which typically connects from the metal fuel line on the frame rail to the pump on the engine. If this hose is getting hot, it could be pinching shut, which could indicate that you have a restriction somewhere upstream (such as inside the tank at the pickup screen).

You can verify this by running a fuel pressure gauge - I made my own setup which tees in right at the carburetor inlet fitting, with a small hose going off to a gauge that I place outside at the base of the windshield where I can see it while driving, carefully snaking the line to the gauge around the end of the hood gasket so it doesn't get pinched shut with the hood closed. This will tell you if you are losing fuel pressure while you are driving.

I can't see vapor lock happening while the vehicle is driving - that typically happens during the heat soak period after a hot engine is shut off and sits. A big block consumes fuel fast enough that you always have fresh, "cool" fuel coming into the carb while it is running.

What kind of carb gasket are you using? Most of the stock ones had multiple layers which insulated the exhaust crossover passage that typically runs underneath the carb. They do make phenolic heat isolator plates that go in between the carb and the manifold to reduce heat transfer into the carb. Some people have insulated the fuel line going to the carb as well.

 

There is nothing wrong with the fuel lines. The metal line on the frame is the largest I've seen. There are no weird bends or kinks in it. It is not getting hot. The rubber lines are brand new. I've only run the car once since the new pump and rubber lines. I have no idea what carb gaskets I have. I bought them from the little performance shelf at advance auto parts. I have two because I'm running a 1" spacer.

 

I had a 72 Torino that did this. Turned out to be a clogged fuel filter. I assume that the debris inside settled over a few hours eventually letting me start it again. Just a thought...

 

well, I feel like a complete idiot now! The reason it died on me after I replaced the fuel pump and all of the fuel line is because it ran out of gas! I completely forgot that it was low on gas. once I got gas in it it ran just fine and the problem is now fixed. The reason the starter was weak when it would die is because the alternator belt was broken and it was low on juice. It's cool that you have a 72 Torino because I also have a 1973 Gran Torino station wagon.