fuel vaporization

[douglas j]

I don't know if this is common with modern fuels, but the car starts then stops when hot, its fine when cold. I have seen these filters that return some fuel back to the tank, any good?

[David C]

Is this problem just when starting from hot? If so you could try a heat insulating spacer underneath the carb. Not all spacers have the same properties. There are wood and rubber based types made specifically to block heat such as the Edelbrock 9266.

Not sure about how filter with return would help assuming it's in the feed to the carb.

[Roger Morrall]

Originally Posted by douglas j

I don't know if this is common with modern fuels, but the car starts then stops when hot, its fine when cold. I have seen these filters that return some fuel back to the tank, any good?

It may merely be because it’s running too rich on idle. Try adjusting the two idle jets in a tad. If they’re already right in come back to me.

[douglas j]

Thanks for the reply, the car starts well when cold and runs at a 800 rpm idle, smooth and no spluttering or coughing. I have set the CO at about 2.5. After driving until hot and leaving it for 5 mins starts well and is fine, if left for about half an hour it starts then stops, it does start again but needs a far bit of churning. I suspect the fuel is boiling up and causing the problem. It all adds to the fun of modern fuels in older cars.

[David C]

I had this issue with both of my 410s even with the fuel available 35 years ago. Fitting a heat insulating gasket under the carburettor made a dramatic improvement.

[douglas j]

Thanks for that, I will make up a part and fit. All my troubles will be over.

[David C]

Oh to have so few troubles... (I think modern yoof would insert a smiley face at this point)

As much as I am an ardent fan of informed DIY, unless I am underestimating your expertise in this field I would suggest you modify your expectation of success making a suitable insulator with materials that are readily available.
Per my previous post the Edelbrock 9266 seems to work well and I think has better heat blocking properties than most straightforward alternatives.

Best of luck!

[Green411]

It's a common problem with V8s, with the carb on a cast-iron manifold directly above the cast-iron engine = massive heat soak. On my 411 the problem was exacerbated by the exhaust diverter flap between the driver's side exhaust manifold and downpipe being seized largely shut, so the driver's side exhaust gases passed through the cross-over passage in the intake manifold under the front of the carb, which heated the intake up even more. Or they leaked out through the broken housing. As I don't drive my car in freezing weather, and got so sick of the carb I fitted a Holley Sniper (thus greatly diminished worries about carb freezing) I binned the diverter mechanism and fitted a c.1" spacer plate in it's place, and changed the intake manifold valley pan and gaskets to ones with the crossover blocked. See a 2023 (I think!) BODAcious article for more detail and pics.
So suggest checking that too.
Plus carb insulator as discussed.
You could also fit a low-pressure electric pump to on a separate switch & relay to pump fuel from tank to the normal mechanical pump, to save all the churning of starter motor?
Good luck.

[douglas j]

Thanks for that, very helpful, I will have a look at the diverter valve and follow your instructions. I have fitted an electric fuel pump already which as you say stops all the churning over to start.

[Green411]

The valley pan with blocked heat riser I used was Felpro 1214: intake/lifter valley pan with blocked exhaust heat riser; includes paper gaskets.
If you don't know it, the Mopar 383 intakes are 'dry' (ie no coolant passages) and you don't need to disturb the distributor, so it's reasonably easy. No air leaks yet either!