We have a 1979 Chevy 30 1-ton camper special with a 454. This truck has been driving me insane with all of the problems over the last two weeks. This is a university vehicle and we use it to haul a 1520 40 horse Deere tractor around the state. The tractor is hauled on an 18' fifth wheel and the trailer and tractor together weight about 12,000 lbs. Now about the truck, the truck had a new gm 454 installed in 2003 and has only had about 7500 miles put on the truck in the last 4 years. The past three years the truck has run fine with no issues at all. This year I think everything has broken. So far we have changed the fuel pump, the cap and rotor, plug wires, ignition module, fuel filters, and the radiator cap. The engine is the smoothest running 454 I have ever driven until you get about 30 miles down the road. The engine starts to cut out and you almost can’t get it off the road before it dies. I should mention we run the truck down the interstate at about 55-60 mph. When you get the truck pulled over and open the hood the engine is very hot. The coolant does not appear to be any warmer than normal and the overflow bottle is never full. After about an hour the truck will start again and it runs long enough to get home. The temp gauge isn't working so that is my next fix but beyond that the mechanic isn't sure what to do. My thoughts are to change the oil, flush the radiator and maybe change the water pump. I think that the engine is heating up and causing the gas in the carb to evaporate and stall the engine. Let me know what you guys think, I can use all the advice I can get.

Thanks,
Kyle

Have you changed the thermostat? For emissions they increased the temperature that it opens between the 79 and 03MY Maybe going to a 180 degree thermostat might help.

I would guess thermostat also. And hopefully you haven't baked that engine too many times. You really need to get the temp gauge working again.

It may be the ignition coil breaking down. It definitely sounds electrical to me. If not the coil, perhaps the pickup coil in the distributor.

Don't know if the truck is equipped with a catalytic converter, but it could also be clogged. If it does'nt have a cat. i would say ignition heat soak problems also. If it was the thermastat you would'nt make it 30 miles.

I was going to guess coil as well. That or the Thermostat. If it is getting that hot, you should be boiling the coolant.
That truck being a 79 should not have a converter. I think they started in 1980 for pickups.

let us know what it ends up being.

Kitti first appeared on BB in the 87-88 changeover IIRC... marcdeluca hit it, pickup coil

But first pop off coil cover on distributor and make sure the coil ground strap is there, it's usually left off during a cap change... can't miss it, it's a metal strap, goes in between the coil wires in the cap

Ok so the fix was so easy it was almost stupid. It turns out that the metal fuel line was resting on the block. The heat from the engine was causing the fuel to boil and thus vapor lock the carb. I temporarily fixed the problem with 2 wooden clothes pins, now I’m just waiting on the insulated wrap to be delivered.

Ok so the fix was so easy it was almost stupid. It turns out that the metal fuel line was resting on the block. The heat from the engine was causing the fuel to boil and thus vapor lock the carb. I temporarily fixed the problem with 2 wooden clothes pins, now I’m just waiting on the insulated wrap to be delivered.
Good find/diag. :D

I would commend you on finding that. Most mechanics/shops would scratch their heads and throw parts at the engine and not get it. Good job! :)

I find it amazing that you have the problem while driving down the highway. Usually that would occur at low speed when fuel flow is low and the gas has alot of time to soak up heat. Pulling a trailer at highway speed uses enough fuel that I can't imagine a vapor lock happening. However, if you say it's fixed, who can argue with that?

I find it amazing that you have the problem while driving down the highway. Usually that would occur at low speed when fuel flow is low and the gas has alot of time to soak up heat. Pulling a trailer at highway speed uses enough fuel that I can't imagine a vapor lock happening. However, if you say it's fixed, who can argue with that?

The problem wasn't when I was driving down the highway. I would take an off ramp and as soon as I would hit the throttle again the engine would stumble and die. I can't take credit for the wooden clothes pin idea either. I stumbled into someone who had the same problem with a 454 from around the same time and that is what he suggested.