Mysterious Vapor Lock Incidents

[VAroute66]

I just recently changed out my stock water, which was leaking, with a new high flow water pump and am experiencing fuel vapor lock. I can tell because my clear fuel filter shows fuel full of bubbles, and the car runs badly and then dies at about 180 to 200 degrees engine temperature. Adding fuel manually into the carb bowl through the fuel line to restart the car and moving the fuel line further from the heater hose restores flow for awhile to allow some driving until heat builds up again, and the car dies. Obviously the location of the fuel line is the key since the slightest movement of the fuel line away from the heater hose restores flow through the filter temporarily, but I don't understand exactly what changed since the relative position of the hoses is the same as before unless the new pump carries more heat away through the heater hose. The car runs cooler so the heat is being removed somehow. The fuel line runs in between the heater hose and valve cover and touches neither.

What happens if I remove the heater hoses entirely since I really do not need heat? Seems like this would solve the problem. Anybody done it?

Has anyone installed an electric fuel pump (non-recirculating) in their mid year, and would this help?

I have searched previous threads, and it seems that every situation is different. Any recommendations? Thanks!

V/R
Dan

 

[Kid_Again]

Not sure I can help but when I had vapor lock problems, it was inevitably caused by the rubber fuel hose creeping downward and touching the lower radiator hose. I've never had a problem with heat transfer from a heater hose, though I'm sure it could occur.

Start all over again. Make sure the hose is securely clamped in place because you can't tell when/where the hose will flex while driving.

For heaven's sake get RID of that clear fuel filter next to the carb. You are asking for an engine bay fire!!!!!

 

[VAroute66]

Kid Again,

Thank you for your reply, and I will replace the glass filter.


V/R

Dan

 

[magicv8]

The steel line from the pump should not touch the lower rad hose. To insulate it, slit an 18inch long rubber hose with ID same as fuel line OD and slip it over the line. I even wrapped that in silver insulation tape (from a hardware store) on my car.

IMO the best place for an inline filter that attaches in rubber hose is at the fuel tank hose. I gat my 3/8 inline filter from NAPA to insert there.

 

[Kid_Again]

...all good points



...i am crazy nuts about making sure that the gas line has no point of contact with any of the hoses.....i don't know what your output line looks like but many guys have a short piece of hard line coming from the pump and that attaches to a rubber hose...if that's true, don't hesitate to take the hard line off and use a tubing bender to give you more clearance

...i know that you didn't ask for more advice but i've learned the hard way not to use a plain run of black gas line tubing...for a sb, i use 6AN fittings and ss braided rubber gas line from the bottom hard line to the carb - you can buy AN hard tube to AN adapters and they work fine...the braided hose is more resistant to tearing and the braiding provides and small measure of insulation in case the line falls against the lowere radiator hose...all this is kinda' spendy, though

...you could always replace the rubber hose with a hard line that's store bought or, with a flaring tool, a bender and 3/8" steel hardline from NAPA, you can build your own


good luck

 

[VAroute66]

Gentlemen,

Thanks again for taking the time to provide input. In regards to your recommendation, I have a steel line that goes around the lower heater hose and up to about the height of the heater hose that comes off of the intake manifold. From there, a rubber fuel line runs between the heater hose and valve cover and then to the carburetor. When I add more distance between the hose and the fuel line I get better flow through the filter, and the car will run. However, given enough time, it still vapor locks. Based on your input, I am going center it better between the hose and valve cover, and apply tape to both the hose and gas line. If that does not work, I will try a steel braided line.

What would happen if I bypassed the heater core by plugging the intake manifold heater hose outlet, and running heater hose only from the fill tank to the water pump? Under normal conditions, there is flow through the tank, and in this modified case there would be continuous flow into the tank from the water pump. I do not think it would work. Any thoughts on how heater hose can be removed while still retaining the tank for fill capability? Thanks!

V/R


Dan

 

[JohnZ]

What would happen if I bypassed the heater core by plugging the intake manifold heater hose outlet, and running heater hose only from the fill tank to the water pump? Under normal conditions, there is flow through the tank, and in this modified case there would be continuous flow into the tank from the water pump. I do not think it would work. Any thoughts on how heater hose can be removed while still retaining the tank for fill capability? Thanks!

V/R


Dan

That'll work fine - it's exactly the way the factory did it with the C48 Heater Delete option; as long as you retain the 3/4" hose from the expansion tank outlet back to the water pump inlet, you're in business. The coolant flows from the tank bottom outlet to the water pump, not the other way around.

 

[Tom Bryant]

...all good points



...you could always replace the rubber hose with a hard line that's store bought or, with a flaring tool, a bender and 3/8" steel hardline from NAPA, you can build your own


good luck

That's what I did on my project. It isn't hard to do and eliminates the possibility of a rubber hose inspired engine fire. I have a cheap $10. bender and an inexpensive Eastwood double flaring kit. I bought some pre made sections of 3/8 brake line from NAPA and then cut and bent them to fit. That way you only have to flare one end. You can use the lower part that you already have if it comes up the front of the engine far enough to attach to a GF90 filter then bend up a line from that up to the carb. This way you can route it away from any heat source and it will stay where you put it.

Here's a couple pics of mine. The fuel filter is a tad overkill but it's cool and I made a heat shield for the back side just in case. The carb is a '66-67 type Chevelle/Chevy II Holley.

 

[JohnZ]

Nice tube work - you're hired!

 

[Kid_Again]

..yeah, i flunked "Hard Tubing Bending 101" and just use AN fittings now

nice work is RIGHT!!!!

 

[Tom Bryant]

Thanks. I was rather amazed that I did it without making a second trip to NAPA to replace lines that I kinked or bent the wrong way. :L

 

[VAroute66]

John Z,

Thanks for clarifying the direction of flow. That helps alot.

Tom,

Really awesome set-up. Thank you for the pictures and advice.


V/R

Dan

 

[Tom Bryant]

You're welcome.

The problem I see with no heater is cool humid evenings when you need a defroster to keep the windshield clear. I'm sure there is a cure without deleting the heater.