'85 C-20 454 Vapor lock?

[Dave]

I have an '85 C20 with a 454 when idling in hot outside temps, the gas will start to boil. Running about 9.5 cr, 400 hp, w/ ceramic headers, 180 stat, 4 core rad w/ dual electric fans, trans and oil coolers.

Installed s/s braided gas line from mech. pump to carb, still wants to vapor lock. I never knew this, but I found a C-30 with a factory fuel line on the outside of the frame rail, then comes over top of the frame transitioning into a rubber hose back to the fuel pump.

Is this what I need? Anyone else experience this problem?

Thanks..

[tucsonjwt]

I have an 83 C20 with the same problem. I wrapped the fuel line with Tec tape (like header wrap) but it did not help very much. My truck is all stock 454. I depress the accelerator all the way to the floor when starting with a hot engine, and keep it depressed a few seconds until the engine starts - it works but makes people think I am intentionally revving the engine on startup. Combine that with "starter heat soak" you get with big blocks and hot starts are a challenge. I used remote solenoid, dual start batteries, and GM high torque mini starter for heat soak. Make sure your fuel inlet nut is tight - mine was leaking a bit which assured hard starts with a hot engine. Of course, make sure your cooling system is in good shape - coolant a little low will cause a 454 to heat up even more than usual in hot weather. If your truck is stalling at idle due to vapor lock, then I think you might want to wrap the whole fuel line where it passes the engine and exhaust, but that might not work either. Wrapping the headers is another option. Big blocks just run hot, which is nice in the winter but not so nice in the summer.

[njlimbaugh]

Put an electric pump on the truck, as near to the tank outlet as you can get it. Hook it up with a toggle switch so you can run it when you want. It will push vapor lock through. Keep the stock pump in place. Neither pump will know that the other one is there.

[flamingbig10]

I'd try a carburetor spacer

[LONGHAIR]

I would go along with the electric pump too, but not on a toggle switch. I wouldn't run it through the mechanical pump either. You are just subjecting the fuel to more heat by running it into that pump that picks up block heat.

The electric pump keeps pressure against the entire fuel line which minimizes vapor-locking. Stick with metal lines, which minimizes the chance of leaks......fires

[rixjohnson]

I had the same problem yesterdaY pulling my toys to the dEsert.im goin with an electric pump hopefully it helps,but engine temps with mechanical temp only gets to190 ,200 with ac running.
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[njlimbaugh]

I've run the electric pump (with toggle switch) through the stock pump on 5 vehicles, starting with a 49 Ford pickup. The fuel won't pick up any heat from the electric pump because there's no resistance in the valves when the pump isn't running. And, as you said, the electric will push vapor lock through anything between itself and the carb. If you run the pump all the time, all you're doing is increasing the line pressure which could unseat the float valve and flood the engine.

[LONGHAIR]

It's the mechanical pump, which is attached to the block that has the potential to add to the fuel line's heat. There is no reason to run it if you have the electric pump.

Oh.............regulator.

[Dave]

First, I'd like to say thanks to everyone for their input!

After looking at all the suggestions, I'm going to go with an electric pump and will probably eliminate the mech pump. I have a pressure regulator installed right now and I know I'll need it for maintaining the correct fuel pressure for the carb.

Now, what brand elec. pump and gph would I need?

Thanks again.

[SSC's76]

Does not matter which brand you run as long as its a rotary pump. I dont have a provision on my block for a mechanical so all I have is a rotary on the frame no issue with vapor lock. All the parts stores can get these pumps they work great very reliable. : CRT-P4070 carter summit part number would be perfect IIRC its the same i have. A few months ago put one on my brothers 86 we got that one from advanced auto airtek brand seems to be working ok.

[Dave]

Thanks to all again! Looks like I'll be ordering a electric pump.

[INSIDIOUS '86]

would look at getting a 165 temp thermostat as well to get the temps down

[LONGHAIR]

Originally Posted by INSIDIOUS '86

would look at getting a 165 temp thermostat as well to get the temps down

A lower temp thermostat will not necessarily make it run cooler. The cooling system has to be up to that task, or nothing will happen, except slower warm-up in cooler weather.
Even if it did drop the coolant temp by exactly 15 degrees....would that really sure a vapor lock condition?
Most of the time it comes from the fuel lines picking up exhaust heat along the frame rail, near the headers, from the mechanical pump, etc...this is the point of the electric pump...and mounting it in the rear. The fuel is in the line "under pressure" rather than being "drawn"(vacuum) by the mechanical pump up front. The pressurized fuel is far less likely to "vaporize" causing bubbles in the lines......reguardless of actual temperature.

Besides, "cooler" is not necessarily better anyway. There is a point to proper "operating temperature"....especially on later model vehicles with fuel injection.

[mooseknuckles]

x2 on the carb spacer.