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I am having a problem with my 71 LT-1. I drive for a sort distance (maybe 5 miles) and at a light the idle will become erratic. If I let it go it will die but start up with the accelerator to the floor. When the erratic idle starts it will cough when I give it some gas. If I keep the RPMs up (1200), there does not seem to be a problem. The temp is below 160 more like 130-140. What has been done, the original Holley 780 has been rebuilt twice and flow tested twice, fuel at proper levels in both bowls, new water pump, new fuel pump and filter, fuel lines have been wrapped with reflective tape, timing set and rechecked. The air from the fan blows hard at all speeds. I use non Ethanol Premium Gas, inspection in the tank shows no corrosion. This happens in all weather although if you kick in the secondaries the process will happen sooner. I have looked at vapor lock but the car will start up and idle ok after it dies. Any help would be appreciated.
Hi Big2Bird, The sock in the tank looks to have been replaced, it is black in color. I disconnected the fuel line and fuel gushed with pretty good force. The lines at the pump are correct. I thought that if it was fuel starvation from the tank it would not startup without any problem.
Hi Big2Bird, it is black so has it has been replaced? From the carb to the fuel pump is steel along with the inlet side. So collapsing shouldn’t be a problem.
Thanks
Hi Big2Bird, it is black so has it has been replaced? From the carb to the fuel pump is steel along with the inlet side. So collapsing shouldn’t be a problem.
Thanks
I doubt it.
Upper picture is an old sock that was cut off because it collapsed.
Lower picture are the incorrect hoses at the pump.
Your hard line to carb is after the pump.
Last edited by Big2Bird; Jun 19, 2020 at 07:52 PM.
There is a hard line going into the fuel pump and a hard line going to to the carb. After going through the records, the sock was replaced six years ago. It could be possible that that it is plugged.
I can't say what the fuel pressure is, that is why I decided to replace the fuel pump. What problems would I create if I were to use some compressed air on the feed line to the tank?
There is a hard line going into the fuel pump and a hard line going to to the carb. After going through the records, the sock was replaced six years ago. It could be possible that that it is plugged.
Okay, so it was replaced. Rule that out.
I have never seen a hard line going into a stock pump. Can you post a picture?
Hey Big2Bird, You are correct!!! There is a rubber hose on the inlet side. It is a molded hose coming from the hard line attached to the frame. Looks to be pretty new.
Does it have a heat shield under the carb? I know 69 did.
Timing is checked, meaning what?
If the distributor springs are weak, or the vacuum can is wrong, it can be erratic.
The Holley I defer to Jebby or Lars or.............
Is your idle too low?
Check the 4 primary and 4 secondary fuel bowl / metering plate bolts and make sure they are tight and no metering plate gasket leaks. Might be well to replace fuel bowl and metering plate gaskets while your at it. They can compress and dry out if car is not driven much. Also make sure no vacuum leaks around the throttle plate to main carb body. You would have to remove carb to tighten Phillips screws if they happened to have loosened. Hopefully none have stripped threads. Your symptoms sound familiar to me with my 70 LT-1
Bullshark
Why is your engine temperature that low?
Did someone remove the thermostat?
When it stalls have you looked down the carburetor throat to see if gasoline is dripping into the carburetor throats?
... Your symptoms sound familiar to me with my 70 LT-1
Bullshark
Ditto. But some new things to check.
The fact that mine also idles fine a few minutes after being shut off seems to indicate it is not a temperature related problem, yet it is not a problem in cool weather...
71 LT-1 Holley Problem
