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Blind man throwing a pitch...is the electric fuel pump being left on after you shut the car down? Residual pressure in the line getting past the regulator if shut off at same time as ignition?

Good thoughts! I believe I had turned off the pump but since it is under the passenger seat, it might take some time to drain down the pressure.

I was thinking that the fuel in the line from the mechanical pump to the carb may be expanding due to the heat after engine shutdown, thus building enough pressure to overcome the needle valve and relieving the pressure through the carb.

I will continue to chase the problem as the weather remains hot the rest of the week.

Thanks for all the suggestions,

Rod

Does it do it if you are just running on the mechanical?

ok. U rebuilt the carb. It runs just fine EXCEPT for engine shut down carb flooding. Bowl vent is not restrictd.

TH eonly remaining problem is the gas that is caught in the ACCLERATOR PUMP chamber. It must thus be boiling and forcing out into the high speed nozzel (what u call main jet tube).

Try this as a diagnostic:
When u turn off the engine then puss the accelerator pedal all the way to the floor, hold it there and put a brick on it to hold it down. If that prevents the flooding then we'll take action to prevent the boiling of gas in the accelerator pump chamber.

NOTE that setting float level lower by about 1/32" (no more than 1/16" MAX) mite very well help too. But this tactic has no relation to the possible boiling of gas in the pump chamber.

As a temprary work-around:
Elemninate mechanical pump from the plumbing. Turn off e-pump about 1 minute before turnoing off engine.

Hello, A possible cure to the problem of boiling fuel in the carburettor, would be to install an insulating plate between the manifold and the carburettor. if you make this sufficiently large so as to shield the bowl from the rising heat from the exhaust manifold it should help.
regards, dnielsen

Well, I did not get a chance to drive the car in the heat today but I did drive it in the cool of the morning and had no problems. I did not even need to turn on the electric pump. I will probably get a chance to drive in the heat tomorrow.

In the mean time, I built a "pan" to go under the carb to capture any fuel before it can run down on the manifold. I have attached a couple of pictures of the pan before I installed it on the car.

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Well, the saga continues! I took the car out this afternoon and the weather was hot, probably in the high 90's. It did really well in traffic without the electric pump but as soon as I tried to climb a grade it started to vapor lock. Turned on the elect pump and all was well. The water temp was in the 180 to 200 range but never boiled.

Got home and was checking things out with the air cleaner off and I got a shot of fuel that must have been more then a foot high out of the carb throat. Not sure where it came from but it only did it once. Had the air cleaner been on I would have been none the wiser.

I know the heat riser is closed because the temp differential is extreme between the bottom and top sections. Top about 165 and bottom about 500!

The carb bowl seems to running about 135 degrees. I think the aluminum pan I added under the carb, in addition to catching raw fuel, is acting as a heat dissipator.

I think the car does not like to run in temperatures above about 85 degrees!! The electric fuel pump running at about 2 psi seems to cure the vapor lock problem but I still do not understand what is going on in the carb??

Rod

Mite have to remove heat riser and block off any passage or exposure to the intake manifold from the exhaust manifold. THis will require unbolting the exh manifold from the intake manifold.

Some V8 owners have blocked off or greatly restricted exhaust/manifold heat passage. Need to use stainless steel to block it off. Any other material will burn thru.

Blovcking it off mite require a longer warm up period in very cold weather, but maybe not either.

PV8 brings up a point. There was at least one post and some photos of a manifold having a large hole burned thru the casting separations. Don't remember exactly where or if there were symptoms which led to the finding. Maybe someone remembers that discussion or can furnish details first hand.