Double wall exhaust system, anybody do it ?

[mtnmankev]

I am still trying to eliminate my vapor lock issues on my 83 C20, I have wrapped the fuel lines running along the frame with heat wrap tape, replaced the old electric fuel pump, and still have the problem.
I wrapped the exhaust pipes from the manifolds to the mufflers today, and hope it helps, but I know the fiberglass wrap isn't permanent, and if the heat is as bad as I suspect, it will burn through the wrapped pipes like it did on the headers that came on the truck that I had to wrap to eliminate starter heat soak issues.

I am thinking now my final solution may be to go with double wall exhaust pipes, perhaps a 3 to 3.5" pipe (probably from a diesel pickup) surrounding my current pipes, and welded with braces to make a space to allow for air to flow between them.
Or, a set of pipes that fit snugly over my current pipes making the pipes twice the normal thickness..
Any experience or thoughts ???

 

[80BrownK10]

First question is why is it so hot to begin with? Is your timing right? How many HP are you making? Are you racing this thing?

I'm no expert but it sounds like you have crazy amounts of heat for some reason or some problem that is causing this.

 

[mtnmankev]

Stock 350 Goodwrench engine, Q-jet carb on a Edelbrock intake.
Engine temp runs right at 165 to 180 depending on speeds driven.
No racing, it's just a normally driven pickup to go to the store and run errands.
Timing is spot on perfect, no pinging, no over advanced hard starts, and no laboring from late timing.
And yes, I agree something is awry to cause the heat issues, but I have checked everything to no avail, and I have not seen this happen on other vehicles.
It's driving me nuts, but then again, if anything weird is going to happen, it happens here.

 

[legopnuematic]

Sounds like theres some bigger thing going on, my 76's passenger header is about 1/4 to 1/2 from the fuel line at the closest point (behind engine mount above starter area), no heat shield on the starter or anything. Never had any problem with vapor locking or anything even in the 90+ degree weather we have been having here and pulling trailers and hauling scrap.

 

[mtnmankev]

The vapor lock problem happens on warm to hot days, above 60 degrees.
And starts after a highway run.
The fuel line coming over the crossmember to the switch solenoid will quit drawing gas, so I switch to the passenger tank.
It resumes pumping gas, and after a while it quits.
I get out with a spray bottle of water, and douse the fuel lines, electric pump, and switch solenoid to cool them off, and the gas will start to flow again.
I figure if the crossover line can vapor lock, it has to be from the exhaust system heat.
The passenger exhaust pipe is a good foot from the pump and lines, etc ....

 

[mtnmankev]

Is there a possibility the Goodwrench engine is a high performance one that can cause these problems ?
I have no way to ID it as such, but it does have a bit of a lope to it idling instead of the normal "smooth idle" from a stock engine.
And that engine sure does have balls, even with close to 100K miles on it, it will flat boogie and haul ass down the road, accelerating with no arguments.

 

[C10MixMaster]

I am still trying to eliminate my vapor lock issues on my 83 C20, I have wrapped the fuel lines running along the frame with heat wrap tape, replaced the old electric fuel pump, and still have the problem.
I wrapped the exhaust pipes from the manifolds to the mufflers today, and hope it helps, but I know the fiberglass wrap isn't permanent, and if the heat is as bad as I suspect, it will burn through the wrapped pipes like it did on the headers that came on the truck that I had to wrap to eliminate starter heat soak issues.

I am thinking now my final solution may be to go with double wall exhaust pipes, perhaps a 3 to 3.5" pipe (probably from a diesel pickup) surrounding my current pipes, and welded with braces to make a space to allow for air to flow between them.
Or, a set of pipes that fit snugly over my current pipes making the pipes twice the normal thickness..
Any experience or thoughts ???

Im in AZ also so im dealing with heat related issues to. my fuel pressure drops to less than 2 psi on hard acceleration the hotter it is the faster it happens i attributing it to vapor lock also. If you have a return line system that was gms way to deal with it initially. from what i can tell a in tank pump with a regulator at the carb and a return line is the best solution.

here's a study done by gm in phx Its a little hard to read but has some good info http://truckroadservice.com/barth_attachments/Chevy_P32_vaporlock.pdf

 

[mtnmankev]

Is it possible this engine does not like ethanol in the gas, causing the problems?
All the other vehicles and generators and equipment here run fine on ethanol gas (I always buy at the same gas station and run everything on it).

 

[mtnmankev]

I am going to try two experiments on the truck.
1. Ethanol free gas, sure it costs more, but may do the trick.
2. Premium gas, again more expensive (a LOT more for my already stressed budget) but may help even though the engine does not require that high an octane rating.

 

[C10MixMaster]

Is it possible this engine does not like ethanol in the gas, causing the problems?
All the other vehicles and generators and equipment here run fine on ethanol gas (I always buy at the same gas station and run everything on it).

that would be a possibility. Different gas station run different blends and the blends change during the year winter gas and summergas are formulated differently. We live in kingman if we fill up here and drive to phx our s10 blazer even with fuel injection will vapor lock and stall out,if we fill up in phx most of that problem goes away because the RVP (Reed vapor pressure) has a lower number in phx. Its easy to try a different station and see if a different fuel helps.

not all gas has ethanol in it and there is a simple test to tell.

 

[mtnmankev]

Now to find a graduated cylinder to do the ethanol test.
Remember, the town I shop in is Prescott, an old indian word that means "you gotta go to Phoenix because we don't have it here".

 

[idahovette]

Kevin, at least you are maintaining your humor!!!!.........so far

 

[mtnmankev]

Kevin, at least you are maintaining your humor!!!!.........so far

Well, Perry, what other choices do I have, what with my health and so many other things around here failing ?

 

[Frankenchevy]

I’m guessing with the clickity-clack fuel pump you’re running a return-less fuel circuit?

If so, you can pick up one of those fuel filters with a built in return and run the return to the 5/16” barb on the sender.

Also, most generic electric fuel pumps will put well over 10 psi through a 3/8” fuel line. So essentially the pump is being dead headed and will overheat and/or prematurely fail. Make sure the pump is below the tank then try this order in the engine compartment: return style fuel filter, fuel regulator, then fuel pressure gauge. All those parts from spectre or mr. gasket should be relatively cheap, yet reliable. Or you can buy a return style regulator, but they’re a bit more pricey.


I’m guessing trying to double wall an exhaust will end in rattles that will drive you nuts.

edit: is there a reason you aren’t running a mechanical fuel pump with return?

 

[mtnmankev]

Thanks, Guy ...that makes sense, and worth looking into.
The fuel pump I got from NAPA is rated at 4 to 7 psi.
I guess now I need to dig around and find the diagram of how the switch solenoid is plumbed so I can hook up a return line.
I hope the parts store person doesn't look at me like I have 3 heads and I'm from outer space when I ask for a fuel filter with a 5/16 return line fitting.