Can't figure out why truck won't start up properly???

[naystcb]

Ok, so I have an earlier post that touched on this subject but I felt it necessary to start a new thread because I have done everything that everyone had suggested to try and remedy the problem but still cannot get my truck to start up and run like it should.

I have a 1971 Cheyenne Longhorn with a 396 that I have installed an HEI on it because I originally thought that I had a distributor problem that was causing loss of power. After installing the HEI I was having problems with the truck not starting right up and idling rough as well as backfiring.

I have since restabbed the distributor and made sure it was on TDC, it is now timed between 10-12 degrees BTDC, I have installed new pre-made 8mm wires, new spark plugs gapped at .045, have already replaced the rotor and cap on the HEI as well as the coil because I thought maybe the ones that were on the HEI I installed were bad. I have also considered the possibility of an intake leak so I pulled intake off and replaced gaskets and inspected for leaks after. I have replaced all vacuum lines. Yesterday I installed a new Edelbrock 1411 750cfm carb with a new fuel filter and fuel lines and gaskets which I have double checked to make sure are sealed properly. I have checked the fuel pump for proper psi and functionality. Shoot, I even changed the belts and a few coolant hoses while I was at it. I have checked the brake booster vacuum hose that goes into the intake. I had the exhaust completely redone from the exhaust manifold to the rear with dual flowmasters....I have changed the oil and filter...I have done just about everything that I can possibly think of that could be a culprit in this problem except for replace the darn PCV valve, I did change the hose though, and I still cannot get the darn truck to fire right up and run as it should.

When I fire up the truck it doesn't start with the high idle that the electric choke should induce to warm up the truck and then kick down, instead when I fire up the truck it will crank over until I give it some gas and then it will run for a second and then sputter out and stall. The only way I can get the truck to run is to fire it up by pumping the gas, and then hold the accelerator down until it warms up but even then I have to have the idle screw set so that the truck will idle at approximately 1200 rpms all the time or it will simply die..even when the truck is warm. On very rare occasions I can turn the idle down to about 1000 rpms but the next time I start the truck up after it has sat for a day or two it will have to be turned back up or it won't stay running. I don't know what the hell is wrong but this is causing me to lose sleep and hair!!!!

If anyone has any suggestions as to what the hell could be wrong....PLEASE HELP!!!!


IT WOULD BE GREATLY APPRECIATED!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!