Ok this is a problem that is growing progressively worse.

The engine will cold start perfectly and idle like a dream once it starts, and it will drive perfectly for 5-15 mins with no problems...but you drive it enough to get it warm and it will continually stall out, it feels like its not getting its fuel, it just stalls and once it stalls it wont start until you let it sit 5-10 mins, then it will again start up perfectly, idle like a dream, go for a few mins then stall again, it seems related to how warm the engine is...the engine isn't overheating or anything like that but its still summer here in FL so it only takes a few mins for the engine to 'warm up' this time of year and once the engine is warm it seems to stall. It feels like a fuel system problem but not one that I'm familiar with, please help

thank you

 

it could be a lot of things.

maybe fuel, maybe vapor lock...

Does it burn oil? Is the exhaust clean or does smoke come out of it ever?

 

the engine is pristine, doesn't burn oil, doesn't smoke, like I said when it starts it sounds like a dream, perfect idle, everything feels exactly as it should be, when it gets hot it starts to stall, let it sit an hour it will fire up and drive like nothing is wrong

 

you can remove the fuel line from the carb and place it in a glass jar just after it dies and crank the engine over and see if the fills the jar in a few seconds.

if yes fuel is probably not the issue.

next try a phenolic spacer to reduce carb temp...some cars need them some dont.

-Gun

 

ok i'll try that, what pray tell is a "phenolic spacer" and where does that kind of thing get installed and how does it benefit, etc etc

 

I had a similar problem with my 66 I6. Started and ran great, died after 15-20 minutes, let sit started up again.

Remove your air cleaner after it dies. Hit the gas pedal and see if you are getting any gas into the carb. I was getting gas so I knew it was not a Vapor Lock or fuel filter..

We pulled a plug and found out we didn't have any spark. We traced it to a wire from the coil that went to the dash. There was a male/female connector on the wire that when the car warmed up the connection failed. Replaced the connection and have not had a problem since.

 

A phenolic spacer is the part between the carb and the manifold. It is made of phenolic resin. You may or may not have one. I've heard many arguments about whether this is a useful component or not. It has to do with giving the fuel/air mixture a little more mixing and cooling space before it is pulled into the cylinders for a better burn. I recall being told that it's only useful at higher RPMs. A race car mechanic told me that my 289 would be better off without it.

 

OK so I tried the simplest solution and replaced the fuel filter and it made no difference. It is definitely related to the temperature of the engine, its almost like there is something that is turning off and not feeding it fuel when it gets warmed it.

Also this problem came on gradually. I first noticed it on an hour long road trip...on the way home was the first time it started acting up, but it didnt stall outright, it just got mushy like it was starved for fuel (this is at highway speed 55-65) but it otherwise made it home.

I've got an old shop manual that suggested it might be related to a faulty or miscalibrated dashpot but I dunno. I'm trying to think of what would be causing this beahvior that would be related to heat???

 

What do the plugs look like? And does is smell like raw fuel when it's warmed up and running? It could be vapor lock as well, or possibly an ignition issue.

 

After a TON of reading up on this I'm becoming more and more convinced its vapor lock...I live in FL so its insanely hot and humid from june thru october, for instance it was around 93 today when I was out driving. I've noticed that when it stalls out the engine is very hot so it would make sense that its hot enough that its boiling the fuel in the line and thats whats causing my problem. I've read several possible solutions and wanted to see what you guys thought the best way to go was:

1)phenolic spacer under the carb, I've heard even a 1/4 inch spacer can make a big difference
2)using heat shielding on the fuel line to prevent heat transfer
3)relocating fuel lines away from heat sources
4)replacing the standard fuel pump by the carb with a rear mounted pump back by the tank, so rather than pulling fuel you will push it
5)a bypass regulator fuel line that cycles excess fuel back to the tank ensuring that cool fuel is always being cycled into the carb

to me the first 3 options sound like the best options to try first, any recommendations on materials? I have the plain steel fuel lines, do they make fuel lines that are specially shielded? Or alternately can I buy some kind of insulation for near the carb/pump?

thanks!