Trouble in the Heat. Please advise

[phlegm]

Issue: I was driving about 30 min today on the interstate, got off the exit ramp, no problem. I made my left and started through the gears (3spd manual). in 2nd when I got to maybe 2.5 RPM the truck started to loose power and then surge back. I pulled off and drove around a lot for a while. at low speeds there is no problem, I can go through to 3rd @ 30 mph. When on the road and at higher speeds that is not the case, and it started the same thing again. when I got back to the interstate and it did on the on ramp, I noticed that when I pushed the accelorator my RPMs were not climbing. I held it down and once everything caught up on the interstate, it was 60 mph the whole way. then when I exited to go home, the same issue came up again.

Environment: I drive the vehicle on the interstate about once a week, usually not that far, but speed is not an issue and this is the first time for this. It was the hottest it has been in 13 years here today, we broke 100dg. and the truck has been local to this area since its original sale.

My Ideas:
Vapor lock -- I have limited expierence with this, only when I ran out of gas once @ 16yrs old. The heat makes me think of this.
trash in the fuel line or jets. -- I only say this because it happens at the top of 2nd and 3rd (until I level out). It could be when the 3rd and 4th barrels come open, if they are gummed up.
overheating on the manual tranny -- Oringinal thought, but the fluid was new when I checked the other day so vescosity breakdown is unlikely, plus with the RPMs not moving while trying to acclerate that leads me to the fuel system.

Again I am new to wrenching my own please help!

[phlegm]

O yea and hard to start today, all day.

[LUV2XCLR8]

Could be all of the above, or something totally different, but I know the
vapor lock thing is pretty easy to fix, just need to relocate and or use a
insulation barrier of some type on the fuel lines near the block, I had this
happen to me once, did everything you said, however that doesn't mean
that you are having the same problem, if it just started I would check in
to the fuel line / fuel filter / fuel sock in the tank, this has burned me to.

[cdowns]

could be a tuneup problem how long ago was a tuneup done/ plugs changed or gapped recently?points set recently?/hei low voltage wired with resistor circuit??/ vapor lock does the fuel line rest on the block or the manifold?? if so it shouldn't /fuel filter been changed recently??/leaking vaccume hose?

quick fix and check for vapor loc is to wrap crinkled up aluminum foil around the fuel line

[knsmodels]

especially the fuel filter thing....I would check that first...

[phlegm]

insulation barrier of some type on the fuel lines near the block

]

So a combo of air temp and heat from the block evaporating in the fuel line before it hits the carb. is there a seprate fuel line for the 3 and 4 barrel? if so that would make a lot of sense. This only happens during heavy acceleration like I said, low speed and when plained out it goes just fine.

what kind of barrier would you rec?

[LUV2XCLR8]

Originally Posted by phlegm

what kind of barrier would you rec?

Show truck or Daily driver?

On my 70 we used the foam pipe insulation,
kinda like you use under your house, I know
it sounds cheasy, but it was my Daily driver
so I really didn't care, if it is a show truck, I
have no idea, but I'm sure others here will be
able to give you more Ideas also, the sock in
the tank did the same thing to me also, it had
the exact same symtoms, turned out the sock
had a cut in it, and the tube was blocked to a
point where only half of the fuel was flowing,
this can be checked w/ a fuel pressure guage,
hope this helps, like I said, could be NOTA

[phlegm]

foam pipe insulation

truck is a driver/worker so if it ends up being heat ugly isnt bad its just ugly.

What is a sock in the gas tank (Im a NOOB)

Per PO there was a rebuild 30k ago so it could be time for a tune up.

I will definately check the fuel filter and lines, they are the easiest and work my way up from there.

[cowboy33713]

Howdy;

I'm with the fellas who say check the fuel filter first - a cheap fix if partially clogged. Fuel line check for full flow, that includes making sure any rubber hose sections are not letting air in on the input side of the fuel pump, which a cracked rubber hose can do- lets the pump suck some air along with the gasoline. Check the fuel pump, too. I put on an AutoZone special last week; cost around $15.
Hope this helps!
cowboy33713

[phlegm]

I opened my hood this am to look and low and behold, there sits my fuel line on top of my intake manifold. That may be an inssue on an hour drive in 100 deg. heat... I may change the filter just for kicks.