[Rich-Red86SB]

He's my story, my truck is a 76 GMC long bed 2500 454 with a 400 auto tranny 2 wheel drive. The truck has stock exhaust manifolds, dual fuel tanks with A/C and I've been fighting a vapor lock problem for years. First time it happened the A/C was on (100 degree day) and when I shut off the A/C it would stop. My first thought was a bad compressor just pulling the engine down making it work harder so I changed the compressor.
This seemed to help but the problem came back, so I thought weak fuel pump so I changed the stock type fuel pump (and took it back and got another one on exchange). I'm pullin my race car on the trailer (hot day) up a steep grade trailer and car about 4500 pounds (Cajon Pass for the Cali guys) and the vapor lock comes about half way up the pass acting like it's running out of gas, I limped it to the top and made it home. I thought cheap fuel pump so I went to NAPA and bought a good one, few weeks later same thing again. I read the truck manual and did a flow test on the fuel pump and it passed with flying colors.
I dropped the fuel tanks and pulled the tank socks off (they were dirty but not plugged) and kept the stock filter at the carb . Drove it again pulling the trailer and car and the problem comes back again acting like it's running out of gas going up the pass on a hot day. Now the problem came back again but this time I wasn't pulling a trailer just driving the truck on a hot day going up and pass. I have a thremo gun so I checked the temp on the exhaust manifold and it was about 420 degrees and with the stock pump a few inches from the exhaust manifold I thought it must be heat sink on the fuel pump so I made a sheild out of sheetmetal to sheild the fuel pump. What was interresting was when I put the thermo gun on the frame by the exhaust manifold the frame was 225 degrees and the stock steel line is bolted to the frame (soaking up that heat) to the pump. So I went to my local Heating and A/C parts house and bought a stick of 3/8 insulating wrap (not the 1/2 inch stuff from Home Depot it's way to big) and wrapped the fuel line from the frame to the fuel pump and up to the carb. Another thing is there is so much heat under the hood I made some 1 inch spacers (3/8 sockets work great) so the hood would not sit on the rubber seal that seals it to the body to let some of that hot air out of the engine compartment.
One last thing is gas, it's just not that good anymore with the blends companies mix up to meet air standards (summer blends) , I've read that some gas boils at 225 degrees so it could be a mix of problems that cause vapor lock. Tomorrow I'm going racing and I'll be pullin' the car and trailer back up the grade again so we'll see if my working and the fuel lines and sheild help . Rich