Upgrade Advice & Stalling

[jgf100]

I am hoping for some advice before I go spend money on unnecessary upgrades. 302W with 1k miles after rebuilt. Pertronix distributor. Truck turns on great and idles good to temp. If I am stuck in traffic in hot weather, engine starts to stutter/rough idle and sometimes I need to give it gas at a stop. As long as I am moving, no issues. Was thinking about going EFI(for self tuning) and electric fan(better cooling). Am I going wrong direction? Will these changes help?
Figured its either cooling or timing goes out of whack when temp gets too high. Thanks

[cep62]

Without more info , I'm thinking the carb is running rich and loading up the plugs .
Does it run good until you idle in hot traffic ?
Does it blow out black smoke ?

[jgf100]

Without more info , I'm thinking the carb is running rich and loading up the plugs .
Does it run good until you idle in hot traffic ?
Does it blow out black smoke ?

It does not blow out any smoke. It runs good until I have to idle in traffic. As long as I'm driving, it drives great.

[Jbarnes79]

Do you have power brakes? Does the idle change as you press/depress the brake?

[1972hiboy]

Could it be vapor locking? or possibly a percolation issue. if you think that could be a possibility, you can try wrapping the metal fuel line from the pump to the carb in red rags and clothes pinning them to the line. see if that makes a difference. if its percolation at the carb, is the carb bolted right to a cast iron manifold? I would try a phenolic spacer if it is and see if that changes anything.

[cep62]

What carb are you using? the floats could be too high.
Holleys are easy to adjust.
Do you have a vacuum gage ? That can tell a lot too.

[Fraser]

I would clean out the choke stove and make sure that system is working correctly first, then reset the idle mixture and speed, often times people set things too rich to compensate for a weak choke. And set the idle a little faster than spec., about 800-900.
Low quality fuel could require a tweak of the timing, maybe try it 1 degree advanced from present setting, and see if that's better or worse, you may need to recurve for a custom cam.

[jgf100]

Could it be vapor locking? or possibly a percolation issue. if you think that could be a possibility, you can try wrapping the metal fuel line from the pump to the carb in red rags and clothes pinning them to the line. see if that makes a difference. if its percolation at the carb, is the carb bolted right to a cast iron manifold? I would try a phenolic spacer if it is and see if that changes anything.

Was thinking the same, although I do have a 1" spacer between aluminum intake. Haven't tried out wrapping the fuel line

[jgf100]

Do you have power brakes? Does the idle change as you press/depress the brake?

I don't have power brakes, so no change when braking.

[DuckRyder]

I love EFI however i don't think it is a good idea to go to it to fix a problem like this, figure out the problem then fuel inject it.

If the truck has a proper mechanical fan, shroud and good radiator there's no need to go electric fan.

Id start with the basics fuel pressure vac carb adjustments and timing.

Particularly make sure the distributor is not hanging up on advance and the the idle speed is properly set warm.

Give us some more details maybe we can be more specific.

[Rocky390]

Could it be vapor locking?

+1. Had the exact same issue with my 409 Impala down here in the Florida summer months. OP's symptoms sound exactly what I was experiencing - would run great until I either hit slow traffic or idling.

Beat my head up against the wall trying to figure out what the issue was, when an old mechanic told me exactly what it was - vapor lock in the fuel line.

The fix? A $10 roll of reflective heat wrap tape around the full length of the metal fuel line. Have to do it when it's cool, obviously - and make sure you take your time doing it, double-wrap it all up nice and clean, because why not.

Fixed my issue right off the bat.

[jgf100]

Could it be vapor locking?

+1. Had the exact same issue with my 409 Impala down here in the Florida summer months. OP's symptoms sound exactly what I was experiencing - would run great until I either hit slow traffic or idling.

Beat my head up against the wall trying to figure out what the issue was, when an old mechanic told me exactly what it was - vapor lock in the fuel line.

The fix? A $10 roll of reflective heat wrap tape around the full length of the metal fuel line. Have to do it when it's cool, obviously - and make sure you take your time doing it, double-wrap it all up nice and clean, because why not.

Fixed my issue right off the bat.

Sorry I've been extremely busy with work. I do plan on trying the heat tape wrap on the fuel line. My question is, by "full length of the metal fuel line" do you mean line from mechanical fuel pump to carb or line starting from tank to pump to carb?

[jzjames]

Electrical? Alternator? Coil
At idle, the spark to the spark plugs starts to crap out? Is what happened in my case.

[Rocky390]

Could it be vapor locking?

+1. Had the exact same issue with my 409 Impala down here in the Florida summer months. OP's symptoms sound exactly what I was experiencing - would run great until I either hit slow traffic or idling.

Beat my head up against the wall trying to figure out what the issue was, when an old mechanic told me exactly what it was - vapor lock in the fuel line.

The fix? A $10 roll of reflective heat wrap tape around the full length of the metal fuel line. Have to do it when it's cool, obviously - and make sure you take your time doing it, double-wrap it all up nice and clean, because why not.

Fixed my issue right off the bat.

Sorry I've been extremely busy with work. I do plan on trying the heat tape wrap on the fuel line. My question is, by "full length of the metal fuel line" do you mean line from mechanical fuel pump to carb or line starting from tank to pump to carb?

Good question. I meant strictly from fuel pump to carb. Get in there and wrap it with two layers of that stuff. I found that if you cut the tape in sections is easier to manipulate and kind of crush up against any bends in line. As long as you take your time, that stuff will surprisingly stay intact even on sharp bends in the line and it will stay looking nice and clean.

Also, cut the width of the tape in half so it's easier to work with.

I should add that I'm by no means a pro mechanic, but this definitely worked for me.