Running dual webers. Bot a Carter fuel pump, a new line and relocated the pump up front in the spare tire area. Ran new hoses, aluminum line through the tunnel and new filters to the carbs.

When it's hot, maybe over 80 degrees out; the car starts to misfire and buck after I have been driving about an hour. It will start missing then it gets unresponsive to the pedal. Barely idles and then shuts off.

I have to sit about 20 minutes to cool off then I can start up and drive for maybe another 5 or 10 then it starts again.

Cool weather it runs ok. I did the fuel pump thinking it would fix this. It did get a little better but during these couple weeks of hot weather it stated up again.

Hoping this is a simple fix...touching the carbs is a scary task for me to even think about. Don;t want to screw it up worse.

I don't have any type of temp gauges at the moment.

Before you go fighting fuel pump faults, I'd get a fuel pressure gauge somewhere in-line between the pump and the carbs. This will tell you if you're getting enough pressure out of that carter pump as it heats up, or if there is a different problem somewhere within the electrics. Also, check the hot wire to the pump while the weather is cold, and note the voltage. Then do it again when the weather is hot and the car has been running for a while. My guess is that it is something electrical related to ambient temperature and resistence with the fuel pump, not pump or carb related.

Oh, one more thing to check for.. do you have the plastic isolators between the intake and the head? This will be something that compounds the problem, as the fuel may be getting cooked by the head temperatures through the intakes. I doubt this is the sole cause, but it definitly may be compounding your issue.

that was exactly my fix. once my carbs became heat soaked i could actually hear the fuel boiling in my emulsion wells. i installed the insulater blocks and i also run my fuel lines in fire sleeve. problem solved. it was a 103 degrees all the way home yesterday 108 miles worth and not even a hint of cough or sputter.

How can I check for these insulators? Are they visible? Is it like a gasket? Will I need to remove the intakes? argh.

No, you do not need to remove the Intakes. They are a thick plastic phenolic material that I'd say is a little less than 1/4inch thick. It will look like the entire face of base of the intake manifold.


They look like this. It should be fairly evident when you look down at the base of the intake whether or not you have them.

so these are not just below the carbs they are down where the runners attach on each side?

But if i don't have them; probably don't, I need to lift the runners, carbs, hex bar, etc. to get in there? Are these widely available? Do they really make a difference?

Correct. They are between the head and the intake manifold, and would require the removal of things to install them. They are readily available through the usual parts supply sources.

I think this may be adding to the problem, but it most definetly is not the entire root cause. boiling fuel would likely create a small problem on throttle transition and cruise, but I think you're problem is more rooted in the fuel pump/pressure/ flow area from an electrical standpoint.

Again, You might want to look into getting an inline fuel pressure gauge to ensure that you aren't losing pressure as the ambient temperature increases.

One thing also to listen to with the carter pumps. They make distinct noises, as most electrical pumps do. When the car hasn't been run in a while, and fuel needs to fill the float bowls, the pump will have a higher pitch whine to it. As the bowls fill up, and the floats close the fuel inlet valves on the carbs, the pitch of the fuel pump will drop to a deeper growl as it it building pressure against the valve. Try to recreate the problem, but this time listen to the pitch of the fuel pump. If the pitch is different from cold-hot, you've narrowed down your problem.

Well, did it again. It seems I do have these insulators; one looks a little cracked but they are here.
I also noticed that the rubber fuel lines heat up pretty well too.

Silly question but is the fan belt driven with the alternator? Not sure...maybe the fan isn't turning?

Again, you need to check your fuel pressure. The fan is driven off the nose of the crank, and is always turning when the engine is turning. The alternator is driven by the belt as an "accessory" to the fan.