Vapor Lock caused by Header Heat??

[MICAH1]

I recently made some enhancements to my exhaust system, so on Friday past I took a road test from my home in Fort Washington, Md to Wilmington, Delaware to pick up my son and test the exhaust for leaks and all around performance. The system sings with a mellow growl that turned heads and got a lot of thumbs up . Now rolling south on I-95 I pull into the first reststop for gas but after fill up, the car turns over but will not start. After checking the ignition and gas flow it still won't start. Car sat for three hours and right before I called the tow truck a last turn of the key and it fires right up. Now I am thinking vapor lock so I get home and search the site and sure enough that looks to be the case. I also search the site for exhaust wrap and I see where Rally Bob says not unless you want a new header purchase every year. (Check this site because Bob is right: http://www.centuryperformance.com/heatwraps.asp )
So my question is, beside installing a electric fuel pump, what else can be done other than coating my header to cool down the engine and exhaust area???

[spdkilz02]

man, thanks for the great info on this...this will definately come in handy when i start the project on the manta...it will be producing alot of heat under the hood...

[greensmurf20]

to help reduce chances of vapor lock, try and run your fuel line from the fuel pump, down along the front edge of the engine corssmember, and then up the side of the passenger side inner fender to your carb....it keeps the fuel line away from the heat of the engine, as most have a steel line that goes up the side and around the front of the motor.

otto also has a good few tips, use the plastic wiring loom protector over your fuel line to reduce heat on the lines and use a plastic filter, as it wont absorb as much heat as a steel canister filter. of course the heatshield is a must.

[MICAH1]

Greensmurf20,
I do have the heat sheild under the weber, and the plastic loom protector is all over the gas line. However, I like the fuel line route that you described.

[jeff denton]

Do the electric fuel pump, there are lots of posts about it, especially the safety relay to shut it off when you lose oil pressure. It's just the modern way to move fuel...
Thanks for the link to century performance, that was interesting. Especially the part about "step headers", I'd never heard of this design.

[soybean]

Here is a good thread about the fuel pump. http://www.opelgt.com/forums/showthr...tric+fuel+pump

Here is one about the inertia switch/s that is/are needed when you run an electric fuel pump, also Ottos post has the electric fuel pump nos.
http://www.opelgt.com/forums/showthr...inertia+switch
HTH, Jarrell

[baz]

Originally Posted by MICAH1 Greensmurf20, I do have the heat sheild under the weber, and the plastic loom protector is all over the gas line. However, I like the fuel line route that you described.

do you have the phenolic spacer between the carb and manifold ? if not most of the trouble will come from there as the gas boils off because the carb gets heated by the block and manifold trying to even out the temps around the engine(the carb gets cold when you drive around as the gas trys to take heat out of the system to evaporate)

[MICAH1]

Baz,
I have the spacer, heat shield, and gasket.... gas filter is the glass see thru type.

[baz]

1 option is to find a fiat that has a carb cooler and fit that ,it is a small fan and runs from a temp switch that goes on 1 hold down stud and is ducted to the carb to cool it when you switch off you could use a pc cooling fan and some plastic pipe but would have to find a temp or timer switch to work it (15 after switch off was how long my X1/9 ran for in summer)

[jeff denton]

I put aluminum plates under and above my carb spacer/adapter and then ran a 4" hose duct from the grille opening up the the manifold area. This looked like it could help at speed, but I was concerned about heat building up when the car was doing caution laps or sitting still. So I added a marine bilge blower to the duct, it really moves the air! To keep it simple it is wired to the ignition so it's on whenever the car is, for a street car I would switch it from a thermostat. I have absolutely no fuel or carb problems, because I don't want any and will do whatever it takes to have a very reliable and foolproof car that starts up instantly regardless of the situation... These plates and the blower are clearly visible in my engine picture called "yeah, it's stock" in my Members Album in the Photo's area. If you were to copy it somewhat and do the electric fuel pump your problems should be solved.
Also, my fuel filter is the marine spin on type, these are awesome, I use the same setup on every rig I own. When you have a question about your filter situation, just unscrew it (it looks just like an oil filter) dump it into a jar, you see dirt and water come out of it. You then know what's going on with your fuel. If you have a dirty tank you just check your filter more often, keep a new one with you...

[MICAH1]

Jeff,
I have a cold air intake on the carb, wouldn't that bring down the internal temp of the weber and intake manifold somewhat??? Where does the vapor lock occur, gas line, filter, or carb bowl??? If I design a direct cold air flow under the hood where should it be pointed, the base of carb or the header???

[jeff denton]

Vapor lock occurs wherever the fuel's temp reaches the boiling point.
Remember, when an engine is running, its heat is being removed by air flowing through the radiator. When you shut the engine off, the heat is not being removed anymore, and the underhood temps go UP. Your fuel pump is soaking up heat. Your fuel lines are being warmed up by the radiant heat coming off the engine, no air flow anymore to prevent this. Your intake manifold is wicking up massive exhaust heat, there is no airflow inside it.
Your carb is sitting on top , heat rising into it.
That's another reason I like electric fans, I wire them so they continue to run after engine shutdown to help things cool off.
My GT engine running hard shows about 195 on the gauge, when I shut it off it goes to 210 pretty quickly even with the fan still on. But at least there is still some air flowing under the hood.
Cold air intake to the carb is great, but it's doing nothing when the engine shuts off. No more air flow, right? I point my cold air duct into the area of the two plates to try to absorb heat rising off the intake. But it has to be forced, hence the bilge blower, to be doing any good sitting still, which your car should be if the engine just shut off.
Hey thanks, baz, you're right on top of things.
If you look close at the picture baz moved to my previous post, on the firewall behind the valve cover is a toggle switch marked IGN and a pushbutton switch marked Start. Anyone wanna guess how incredibly handy that is? And I feel it is a safety item, too. The ignition does not have to be on to engage the starter. I don't have the resistor bypass terminal of the starter hooked up, so bumping the engine with this button is very safe. Or if the engine is running and I suddenly want it stopped, the switch is right there handy.
Inside the car, the start switch is a double throw momentary contact toggle. Pushing the switch up will bypass the "no oil pressure, no fuel pump" safety relay, pulling the switch down cranks the engine. That way I can prime the carb with fuel before starting the engine.