Stalls when stopping or down shifting

[Lift]

It seems to be that this v8 swap is just one problem after another, Now that i finally got the clutch taken care of i have been able to test drive her on the road. The only problem i seem to be having is the engine will die when downshifting or coming to a stop and its completely random.

I checked the timing, i checked the carb idles settings and adjusted them all the way in and out 1.5 turns. All the vacuum hoses look to be good.

The only thing that may affect this is im using and aftermarket jacobs ignition with an efi distributor on a carbed 302.

Im not sure what else to do about it i cant seem to fix this problem. I need someone with more professional experience then me to give me some insight on this or possibly even take a look at it thanks.

 

[RonD]

What is being used to advance the timing?
Ported Vacuum?

So the common factor is engine wants to stall after running under load and then returning to idle.
And reving the engine and then letting it idle doesn't cause a stall?

Are you running an EGR system?

 

[Lift]

No egr, im using an electronic ignition from a newer 5.0 fuel injected motor. It shuts off like turning the key off almost like it gets flooded or something.

Supposedly i had the firing order wrong and was a few teeth off on my dizzy. And when i tried to start it after fixing those things it would run awful and backfire and i was told my float in my edelbrock 600cfm was not working right so i took it apart and the float rails were rusted to shit so i went and bought a holley 600 or 650 not sure. But thats another day to come. I have made no progress yet.

 

[RonD]

Could be too much fuel pressure, this is from a Holly carb tuning site:

"Note that some later model vehicles (the 5.0L Ford is one example) have mechanical pumps that will give more than 6.0 psi at idle. The vehicle will perform well, but may be prone to stalls on quick turns and stops with the clutch disengaged. If this problem occurs, check the fuel pressure. If it is more than 7.0 psi at IDLE, it should be reduced through the use of a regulator."

Electric or mechanical pump needs to be below 6psi at idle, edlebrock recommends 5.5psi at idle

 

[sparky2eh]

i checked the carb idles settings and adjusted them all the way in and out 1.5 turns. All the vacuum hoses look to be good.


That is a good setting to start with but you really need a vacuum gauge to set the idle mixture. It sounds like your carb is presently set too lean with the idle mixture settings, hence the stalling after load is removed.
Set the base timing, hookup a vacuum gauge to intake manifold vacuum, set idle, turn one mixture screw till highest vacuum reading and smoothest running of engine, then same with the other screw, set the idle, repeat....
The idea is to get the throttle plate pretty much closed at idle and the idle mixture screws set so that the idle circuit keeps it running this way at the correct rpm, probably 650-700 or so.

Well my 2 cents worth anyway

 

[dangerranger83]

he 600cfm may be a bit much. Also make sure your running the correct pressure to your carb. I'm regulated at 5.5 on my 500cfm edelbrock.

I had the same issues with a holley, turns out my floats needed adjusted and my pressure set better.

Kinda sounds like she is leaning out on you when you let off the gas due to the butterflies closing under a vacuum from being under a load.

But what my edelbrock manual says to check for is float level and drop, flats for leakage, clean and/or replace air horn gasket and fuel pursue its too high and a fuel regulator may be needed, lower float level from 11/32 to 7/16...those are for braking.

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[Lift]

Thanks guys lots of good info. I didnt have a holley on it before, i had an edelbrock but i just bought a holley an will be installing that today, and also for fuel pressure im using an autozone electric fuel pump that runs 4-8psi i believe do i need a regulator for it?

 

[dangerranger83]

I got mine from AutoZone too, mr. Gasket 12S, details about it are in the link.

http://www.summitracing.com/parts/mrg-12s

anyways yes you want a regulator to keep the fuel to the carb constant.

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[Lift]

Ok fair enough, and i believe that is the same fuel pump im using. I have one problem and it is When i get down to 3 gallons or so in my fuel cell it wont pump anymore fuel?? That and it feels like the stock 83 rear axle has terrible rations for the 302 with a t5 very slow to getting up in rpms. I found out the stalling reason is because one of the pins in my edelbrock 600cfm carb was bent not sure what is called but i took it apart replaced the broken pin and rebuilt it and she purrs like a kitten now.

 

[dangerranger83]

Metering rod I assume.

So you have a pump in your fuel cell? Do remember that the fuel pumps rely on the gas to keep them cool and can stop working if they get hot.

Best thing I can say is to not run yourself so low on fuel. You could be running the pump dry if you are braking hard enough or going up a hill.

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[Lift]

No the pump is not in the fuel cell its outside on the frame rail of the truck. the fuel cell is plat inside so i think it might just be a shit design...

 

[dangerranger83]

If it's flat, it's sucking dry on and will burn up a pump quick.

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[gsp]

Swapping carbs should work and yes, 1.5 turns is a good start, you do not need a regulator for that pump.

 

[dangerranger83]

But it is suggested to use a regulator, most companies say to use a regulator. Edelbrocks say to not exceed 6.5psi or you will flood. .5 psi is a lot of pressure on a needle for the floats and I have proved to myself a half psi will cause flooding.

Makes the pressure constant to the carb and tuning easier IMO, less variables.

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