Vapor lock up? Running bad when warm.

[Asahi123]

I have a 71 chevy 350. I have already changed the fuel pump. When the truck warms up it runs ruff up to about 30mph and then after that it runs good. Also runs great when it is cold until it gets to operating tempurater. I thought was the fuel pump changed it out. I have one of those filters you can take the filter out and clean. I have done that and replaced all rubbers hose for the fuel lines and have blown them out. I check the sending unit it looks good. When the problem starts I have tried to remove the gas gap no change. I have the origanal intake with a aluminum spacer and an edelbrock carb. So does this sound like vapor lock? I put the carb on last winter never had a problem with it sense now. It has been getting in the upper 90. So the problem didn't start until the temp started going up. Coolant temp fine. Should I put one of those plastic spacer between the intake and the alunimum spacer? Any help would be greatly appreciated.

[Lee H]

Is the choke opening all the way when warm?
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[trac209]

When you pull the gascap off does it release a vacuum sound or pop off?
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[Asahi123]

Yes the choke opens up when it is warm. No I don't any swoosh sound when the gas cap is taken off. Any other ideas? Do I need to add the phenolic spacer between the intake and the alunimum spacer?

[Lee H]

Thousands of these trucks are running just fine with no spacer. Need to figure out what's wrong with your setup and get it fixed. Throwing money at it in hopes of fixing will just cost you lots of money and you'll likely still have the problem. How long has it been since you have done a "real" tune up? Plugs, wires, points if you have them, check vacuum and mech advance, carb rebuild, not just throw in a kit but a real rebuild.
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[trac209]

Running rough when warm could also be in need of valve adjustment. A buddies car was doing the same running great when cold and bad once warm. You could try that as well in your tune up.
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[Asahi123]

Carb is new put on 6 months ago. Spark plugs,distributer,plug wires. No vacum leaks. Timing 8deg. No issue with anything until it started getting hot weather.
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[Asahi123]

Originally Posted by Lee H

Thousands of these trucks are running just fine with no spacer. Need to figure out what's wrong with your setup and get it fixed. Throwing money at it in hopes of fixing will just cost you lots of money and you'll likely still have the problem. How long has it been since you have done a "real" tune up? Plugs, wires, points if you have them, check vacuum and mech advance, carb rebuild, not just throw in a kit but a real rebuild.
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The money that was spent was 20 bucks the truck only has150,000. The fuel pump has never been changed. So I don't see were you think spending 20 bucks is throwing money at it.
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