Finally got around to wrapping the exhaust pipes hoping to cure the vapor lock problem. The wrap is from Thermo Tech from NAPA, 2"x 50', 56 bucks. I wrapped all the pipe that was near fuel lines, then the down pipes where they were close to wires, oil filter, etc. Still going to clamp the ends and wrap with SS wire at 6" intervals before the 1300 mile road test to Dega. I'll let you know if it works out.

Wrapping pipes can shorten their life. Thorley says no lifetime warranty if your wrap.

Vapor lock can be cut by using a fuel pump back at the tank. Fuel under pressure is less liable to boil than unpressurized fuel.

The fuel line from front to back can be moved to the outboard side of the frame rail to get it away from exhaust heat.

Does your coach have a vapor return line from the pump output to the tank?

We recently climbed from below seal level to 6000 ft in 105 degrees pulling a heavy toad, and the only vapor lock we had was the genset. I give credit to the electric pump Barth installed back there.

bill, I am aware of the fixes you suggest. I have no idea how to install an electric fuel pump, and I suppose I'd need 2, one for each tank, making it even more difficult. The only vehicle I've seen burn to the ground was caused by an electric fuel pump. The vans engine quit, and after a minute or two with the key on the guy hit the starter again and it went up, blowing the doghouse off and instantly engulfing the van. Everyone got out or was blown out but OK. A good friend was nearly killed when his 30 foot Wellcraft blew up in has face because of the electronic fuel pump. I know something was wrong in both cases, but for my peace of mind, if I don't need one [or 2], I'll pass. Re-routing the fuel line was another option, but where it's nearest the exhaust is at the selector switch between tanks, and moving that would require removing the exhaust pipe and muffler, and I'm not up for that much of a rust breaking project. I assume the return line still goes back to the tank, at least it did when I replaced the mechanical fuel pump. So if the wrap cures the problem, which I believe it will, I'll settle for perhaps a little less exhaust pipe life.

You can also install a "Y" pipe and increase the passenger side exhaust pipe to 2-1/2" and eliminate the dual exhaust. On a non-racing 454 in a truck chassis you will not reduce either your performance or mileage.

I mean eliminate the passenger side and run only the driver side.

quote:

So if the wrap cures the problem, which I believe it will, I'll settle for perhaps a little less exhaust pipe life.

Would it not be better to wrap the fuel line?

Dick, already tried the line wrap, but couldn't isolate the area where the tank valve is. When I had it wrapped it worked pretty good but it came unwrapped and fell off. This stuff won't. I forgot to mention that I got a guy in the exhaust fabrication bizz. If the pipe rusts out I'll have him either go back to a single or at least move this pipe over so it isn't a half inch from the valve and lines.

quote:

Originally posted by Danny Z:
I suppose I'd need 2, one for each tank, making it even more difficult.

A pump installed right after the changeover valve would protect all of the lines from it to the engine. Since the engine and manifold heat is up front, this would address most of the potential for vapor lock.

quote:

The only vehicle I've seen burn to the ground was caused by an electric fuel pump. The vans engine quit, and after a minute or two with the key on the guy hit the starter again and it went up, blowing the doghouse off and instantly engulfing the van.

1. Sounds like there was also a flooding carb or a fuel leak.

2. All electric fuel pumps should have and oil pressure switch that shuts off the engine when it is no longer running. The start current bypasses the pressure switch for startup. Some cars also have an impact switch, which shuts off the fuel pump if you hit something hard enough.

quote:

Re-routing the fuel line was another option, but where it's nearest the exhaust is at the selector switch between tanks, and moving that would require removing the exhaust pipe and muffler, and I'm not up for that much of a rust breaking project.

Yeah, I can see that. I like to use sheet metal with an air gap to keep exhaust heat from things. I also wrap some heavy aluminum foil around things I want to protect from heat. That is standard airliner practice, BTW.

quote:

So if the wrap cures the problem, which I believe it will, I'll settle for perhaps a little less exhaust pipe life.

Since the exhaust pipe is not as hot as the headers, it might not be as great a concern as wrapping the headers. I have only read about headers being hurt by wrapping. I remember nothing about exhaust pipes, even though the same principle would apply, but perhaps in a lesser severity.

If you would like a drawing of an easy fit-all heat shield you can cut out of sheet metal, PM me and I can scan and send when we return to civilization.

quote:

Originally posted by Tom K:
You can also install a "Y" pipe and increase the passenger side exhaust pipe to 2-1/2" and eliminate the dual exhaust. On a non-racing 454 in a truck chassis you will not reduce either your performance or mileage.

+1

Chevy did that off and on on their MHs. Some experts say it is better for torque, some say true duals are best. I haven't experimented too much, because I prefer an X pipe. Both Wye and X pipes are quieter, too, because the exhaust impulses are not separate bangs, but are closer together and forced to mingle. This allows use of a less restrictive muffler.