Gentlemen,
79 F150 Ranger Lariat SB 4x4 400ci V8. Truck is running great with 1 exception. Starts & runs fine, after 20ish minutes driving she tries to stall when stopped - traffic light, etc. I have to keep one foot on the break and one foot on the throttle to keep her running. I have replaced 2bb carb with an Edelbrock Performer Carb 600cfm 4bb, which went like butter. Easy start, sounds and runs great at idle until she gets hot.

I'm a driveway mechanic, with enough to get myself in trouble. Input is appreciated

 

Did this start with the new carb? Or was it doing this on the 2V also?

What is your idle speed set at? I take it that your truck is an automatic? You could always try raising the idle a bit.

I would check the fuel pump's output by removing the line at the carb, disconnecting the coil wire, and routing the fuel line to a container. I like a long hose for getting the container and the end of the hose away from the vehicle. Then crank the engine and observe the fuel output. I suppose the pump could be leaking internally when it heats up? I'd check the pump while cold, and then check again when it's hot. Check your oil too, and make sure you don't smell fuel getting into it.

Another good piece of advice is: Inspect your metal fuel lines for any kinks or dents which would impede flow. One of my friends had a '76-'77 Cutlass with a 350, and they put an Edelbrock top-end kit on it, and it never ran good. He sold the car to a buddy - who found that the fuel line had gotten crushed a little, where it runs under the engine. He fixed that, and the car ran great...

And another one which personally affected me: Check all of your soft fuel lines too. When I did my cab swap, I noticed that the short line which connects the tank to the hardline was collapsed. I replaced it and it ran way better.

 

Thanks Meangreen, exactly the advise I was looking for!

 

The way I am reading this is you replaced a good working MC v2 carb for a Edel v4 carb so the intake manifold was changed to make this happen?
This is not a problem in itself as it seams to start & run good other than coming to a stop, am I right?
The problem I see, between the lines, is you pulled it out of the box and bolted it on without any adjusting.

Pick up a vacuum gauge and some way to read RPM if you dont have a tach in the truck. A dial back timing light is another thing that is nice to have but not really needed at this time.
Hook the vacuum gauge to intake manifold vacuum and the tach to read and start the motor and get it up to normal temp.
When out to normal temp the choke should be fully open if not adjust it so it is. Most chokes have a black housing with 3 screws and marked "lean" / "rich".
You need to loosen the 3 screws and turn it a little to the lean side so it is open all the way, dont go too much, and tighten the screws.

Now on the carb there should be 2 adjusting needles I believe at the front of the carb. You want to turn them in & out evenly to get the highest vacuum reading on the gauge.
I would start by turning each one in 1/8 turn, did the gauge go up or down? if down you went the wrong way so turn it out the 1/8 back to the starting point and then out 1/8 turn.
If it went up go another 1/8 turn out on each needle till the gauge starts to drop and go back the other way to get the highest reading for vacuum.

When adjusting the needles you may hear & see the idle RPM change from where you started, it is most likely higher at this point.
You will want to find what the factory idle RPM is and adjust the idle speed to it. If it said "in gear" set it just a little higher as it will drop down when in gear.
Put it in gear dose it still stall? If not put everything back to normal so you can go for a ride and see if it stalls.
If it dose maybe turning the idle speed up just a little over factory may help?

At this point I would like to check the timing and why the timing light.
Motor up to normal temp idle speed set, vacuum hose removed and plugged from distributor not check timing.
You can set it to factory but I would bump it up to 10* to 12* BTDC as a starting point, put the hose back on and recheck idle speed because if you changed timing the idle speed changed too.
Take truck for a drive and if you dont get pinging you are good, if you do then retard timing to say 8* BTDC or pinging stops.
Let the motor set off for say 5 min. and then try and start it it should start normally but if you get kick back like the battery is dead you will need to retard the timing so it will crank with out the kick back.
Most of the time with 10* to 12* BTDC there is no issues.
Hope that helps.
Dave ----

 

Start with basics. Make sure the choke butterfly is fully opening. Connect a vacuum gauge and see where you are at. they are inexpensive if you don't have one. There is a plethora of info available for vacuum gauge troubleshooting/diagnosis. Make sure timing is set properly. Verify vacuum advance module is working.

 

351M and 400 fuel pumps spec at 7 psi. An Edelbrock carb will tolerate about 6 at most, unless you use the gas fast. You need a fuel pressure regulator, like Holley's 12-803, set to limit fuel pressure at the carburetor to 5.5 like Edelbrock recommends. I'm surprised it runs OK for 20 minutes, mine was starting to flood a bit sooner after startup when I first put a Edelbrock on with no FPR, but run damn near perfect after putting the FPR on at 5.5. Now even with a Holley on it, I still run the FPR but set it at 6.5 like Holley recommends.

 

I forgot about that one. Good catch!!!

 

As others have said, start with the fuel pressure, check vac, check idle mixture screws and adjust per manufacturers procedure, check the choke, etc.

also, kinda sounds like heat soak to me. Carb spacer would be money well spent either way, and a fuel filter with a return line so the fuel stays cooler instead of dead heading, sitting, and heating up in the line. Try G3499 on Summit. Look up Uncle Tony’s Garage on YouTube and look at his videos about Edelbrock tuning and tips. Super helpful stuff.

 

Guys
Sorry for the late reply, been out of town. Thanks for all the information, its a tremendous help. This is a project truck purchased for my son and I to rebuild except he went off and enlisted in the Marine Corps halfway through the biuld. So it is now my intention to have it 100% ready for him whenever he returns to civilian life. All the information is great, I will try each and Im sure one of them if not bits of all will take care of the isse.