as per FlowMaster Tech. sheet;
Quote!
"
IMPORTANT!!!
Due to the efficienchy of FLOWMASTER muffers, the extreme heat generated
under the hood is GREATLY REDUCED, increasing the service life of many
components (rubber hoses, belts, plastic parts and exhaust manifolds, etc.)
In the process of lowering the underhood temperature the exhaust system may
in some cases be subject to INCREASED heat. The FLOWMASTER system is
capable of handling this but it is important to install the muffler under
the stock heat shield when one was supplied as original equipment.
If not originallyy present, or for added protection, we STRONGLY ADVISE
installation of heat sheilds on all motorhome applications and/or heavy duty
tow vehicles.
Aftermarket heat shields are available at the most muffler shops or all
aluminum heat shields are available form FLOWMASTER."
reduced under the hood heat....
I use this to emphasize my point about the engine running cooler, but also
to point out that even wtih the stock factory muffler system, on a warm day,
hot pavement, running up grade almost everyones GMC starts to sputter and
loose speed.
What's happening is the heat off the exhaust system flows straight back
over/under the fuel tanks and begin heating the tanks up and begin to boil
the gas creating vapor which then is sucked up by the fuel pump system.
The more fuel in the tank the less effect occurs.
With this new FlowMaster system in place I realized increasing vapor
problems as ambient and operating temperatures increased.
Solution;
Electric fuel pump with fuel filter placed forward of the fuel tank
selection valve; capable of 7-8 psi at 20-30 gph. Then below the mechanical
fuel pump install another fuel filter with return line to tank. Not
neccesary to run a line all the way back to the tanks; run the return line
to the overflow line which runs parallel to the fuel supply line; tapping
into that line at the frame where steel line turns into rubber hose line. I
used a 1/4"line to 1/2" tee at over flow line.
Most important portion of this solution is to reduce the effect of the
exhaust heating the fuel tanks. JCWhitney has 4'x24 or 48' lengths of
heatshield insulation...using plywood 20-3/4"x 48" ; wedged in a diagonal
fassion so as to deflect hot air down and away from the tanks, cover it and
the tanks with the heat shield material, fastening it with "heat shield
mastic" and screws. I also used sheet metel for heat deflection around
exhaust and transitions.
I hope this helps those who have experienced the "I hope I can make it over
this hill " experience.
Later JRBIAVA
Quote!
"
IMPORTANT!!!
Due to the efficienchy of FLOWMASTER muffers, the extreme heat generated
under the hood is GREATLY REDUCED, increasing the service life of many
components (rubber hoses, belts, plastic parts and exhaust manifolds, etc.)
In the process of lowering the underhood temperature the exhaust system may
in some cases be subject to INCREASED heat. The FLOWMASTER system is
capable of handling this but it is important to install the muffler under
the stock heat shield when one was supplied as original equipment.
If not originallyy present, or for added protection, we STRONGLY ADVISE
installation of heat sheilds on all motorhome applications and/or heavy duty
tow vehicles.
Aftermarket heat shields are available at the most muffler shops or all
aluminum heat shields are available form FLOWMASTER."
reduced under the hood heat....
I use this to emphasize my point about the engine running cooler, but also
to point out that even wtih the stock factory muffler system, on a warm day,
hot pavement, running up grade almost everyones GMC starts to sputter and
loose speed.
What's happening is the heat off the exhaust system flows straight back
over/under the fuel tanks and begin heating the tanks up and begin to boil
the gas creating vapor which then is sucked up by the fuel pump system.
The more fuel in the tank the less effect occurs.
With this new FlowMaster system in place I realized increasing vapor
problems as ambient and operating temperatures increased.
Solution;
Electric fuel pump with fuel filter placed forward of the fuel tank
selection valve; capable of 7-8 psi at 20-30 gph. Then below the mechanical
fuel pump install another fuel filter with return line to tank. Not
neccesary to run a line all the way back to the tanks; run the return line
to the overflow line which runs parallel to the fuel supply line; tapping
into that line at the frame where steel line turns into rubber hose line. I
used a 1/4"line to 1/2" tee at over flow line.
Most important portion of this solution is to reduce the effect of the
exhaust heating the fuel tanks. JCWhitney has 4'x24 or 48' lengths of
heatshield insulation...using plywood 20-3/4"x 48" ; wedged in a diagonal
fassion so as to deflect hot air down and away from the tanks, cover it and
the tanks with the heat shield material, fastening it with "heat shield
mastic" and screws. I also used sheet metel for heat deflection around
exhaust and transitions.
I hope this helps those who have experienced the "I hope I can make it over
this hill " experience.
Later JRBIAVA
