Ok, I've got an interesting problem that I need some assistance on. I have a 302 with a 1406 carb, 21214 intake, and 1725 fuel pump (I think thats the right number, i know its the right pump on the car ). Car starts up and idles fine, and while its cold / warm it runs just fine. From idle to WOT it has no issue.

If the car is left to idle for awhile, say, 5 minutes or so, you step on the gas and the car stumbles as soon as the rpms pick up, or even at take off (light or not). If you stop and open the hood, the clear fuel filter is empty or nearly empty. The engine is warm/hot, but not overheating. I can reach in and grab the carb and its barely a little more than warm. You can even touch the valve covers with no danger of burning yourself. Fuel lines are all relatively warm and filter itself was a little hotter (metal ends). No boiling fluid or bubbles coming in from line. Temp level seems to stay around 180 to 185 (give or take).

We took the line apart at the filter and cranked the motor, and were greeted with a pulsing flow a fuel out of the line, as you would expect, but only after like 3 seconds. At which i suspected the line was mostly empty from pump to carb. After reattaching the line, i cranked and started the car, which stumbled at first and the fuel line and filter filled up. I left it idle for a minute with a full filter and the motor stumbled right away and tried to stall. It refused to run properly for the next hour or so.

So now I'm really confused. The motor doesn't get hot hot, or overheat, but visually the line looks like its vaper locking. Can anyone offer any assistance?

Motor info, if needed:
Idle: 650 rpm
Timing: 8 BTC
Vacuum: 20

 

So once the choke opens and the fast idle cam drops is when you're having trouble? Are the idle screw and mixture dialed in? Does it happen only when it idles for several minutes or every time you're driving?

You might hook up a fuel pressure gauge and see what you're getting at the carb.

Crack open the carb and make sure the floats are set correctly and there's nothing odd in the bowls/needles/seats.

Is the sending unit in good shape?

You may have a leak between the tank and pump that's letting air into the line.

If you're talking about one of those glass filters with screw-in plastic ends I'd toss it and get something not so prone to leak.

 

It doesn't start to happen until you've been driving around for awhile, mostly after you drive around and then sit and idle somewhere. After idling when already all warmed up for a little while, then the issue presents itself. Replaced the fuel line from pump to carb last night and issue still remains. We are looking into the line from tank to pump and may be replacing the whole line and tank altogether. Thinking the sock in the tank may be all clogged up. Also looking into getting a 1/2in carb to intake spacer to further isolate the carb from any heat from the motor, in case that might be adding to the issue. In addition, we're rerouting the two heater hoses with more slack as they are major heat sources as well at the moment.

On the carb, the idle mixture screws are dialed in for optimal vacuum, everything else seems to work fine until it heats up after awhile. Pulled the needles as well, just in case they were clogged and they also look fine.

I'll post again when I have more info from current suggestiosn or I get more suggestions with more stuff to try. Thx

 

My 63 F100 Does the same thing with the filter, but doesn't have the drivability issues that your's seems to have. Check the rubber line from the tank to frame line. Sometimes they dry rot and allow air to be sucked in.