Vapour lock in extreme conditions

[discokid]

Ive just come back from racing the Gascoyne Dash in our states north west. We were racing in 40c heat

As most of you know Im running a LS1 in a Defender

After a period of time ( once everything had got really hot)

I had some problems with vapour lock in the fuel system to the point where I couldnt get the engine to run or even re start until it had cooled down

Ive moved the fuel lines as far away from the extractors as possible although the lines do cross above them to get to the injection rails. The lines are also covered in the silver heat proof foil,. This improved the length of time before the vapour lock started again

Im running external fuel pumps and a long range tank

The exhaust runs pretty close to the fuel tank so Im moving that as well

Are there any other suggestions to try and avoid vapour lock

Should I be using smaller or larger fuel lines? Internal tank pumps? Coolers?

[Maggot4x4]

Have you checked your tank breather isn't blocked?

[discokid]

I havent done that but there isnt any pressure building up in the tank

Ill have a look anyway

[ISUZUROVER]

Are you sure this is a vapour lock problem and not a sensor problem (assuming you have EFI)? Not an LS1, but commodore v6s had a common problem that the crank angle sensor would become affected by heat and the engine wouldn't restart when shut off hot. Happened to my dad's, and it would only restart if you let it cool down OR you poured cold water on the sensor.

If it is vapour lock:
Depending on where the heat is coming from will dictate if you want smaller or larger lines. But generally the best idea is to keep all lines and fittings around the same size, and avoid rapid changes in diameter or flow direction at all costs. Maybe your "problem" is really just heat soak???

Btw - whereabouts in Perth are you? I would love to come and have alokk at your landie.

[discokid]

Its funny you mention the crank angle sensor

One of the 4wds I raced against (a Suzuki) was pouring water over his crank angle sensor to get it to cool down and work.

He ended up re directing his window washer bottle water onto it to finish the race

I do race aginst other LS1 powered vehicles (mainly buggies) and I dont think they have that problem. But they may not have standard sensors in them either

I put it down to vapour lock as another landie with a carby chev motor was having similiar problems and he has no crank angle sensor

He moved his fuel lines on Day 2 and it did work better but didnt completely solve the problem

How do you tell?

This only happens when I race up north

You have made a good point about the lines I do have different in and out line sizes Ill make them all the same size

Ill also insulate them and the injection rails and see what happens next year

[ISUZUROVER]

Insulation can often trap heat in and not allow air cooling. I would be more inclined to fit heat shields between the hot bits and the fuel lines.

How much is a new crank angle sensor? Maybe buy one before you next race up north and swap it in if you have problems.

[Loanrangie]

Years ago my brothers mate had a V6 ford capri fitted with a 250 2V falcon six with triple webers and the thing used to overheat and get vaour locks when ran hard, he nade up a small alloy box and ran the fuel line thru it and filled it with dry ice.