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MG TD TF 1500 - Boiling fuel

Hi Again

The fuel in my carb(s) seems to be boiling when engine is warm. The engine starts fine when cold and runs well, but when warm and stopped it has difficulties starting again unless it has had time to cool off.
I have installed a heatshield from Brown & Gammons between the manifold and the carbs with a gasket on each side in an attempt to do something, but it doesn't seem to do anything.
The problem has not always been present, so I'm a bit confused to see it now. The carbs were rebuilt a couple of years ago and have been adjusted by one of the best in the country, so I don't expect that to be the problem.
The engine was rebuilt last winter and the head was skimmed at time, which increased the compression somewhat.
The fuelpump is a brand new SU so the fuel pressure should be OK
Are there any tricks to get rid of/minimize the boiling, which is a minor problem, but still a problem if parked for a short time only?

Thanks in advance
Torben
Torben Olesen

There any number of things that can cause fuel to boil in a hot engine. The problem I had was heat soak from the manifold to the carburetors. Many years ago I had a machinist friend make a couple of spacers from 1/8 inch (3mm) thick phenolic. They were mounted between the carbs and the intake manifold. Problem immediately solved.

I believe these spacers are now commercially available. They weren't back then.
Lew Palmer

Ethanal boils faster than real gasoline. Many things can help, ignition timing, fuel mixture, etc. Foam beverage insolaters fit perfectly on the float bowls and seam to help. Some people swear using wooden clothes pins on the fuel line help to cool the fuel.
Be well,
David
D. Sander

Hi Torben, do you subscribe to the free Totally T-Type online magazine? There is a lengthy series of articles about modern fuels. It might throw some light on your situation. You can find it at ttypes.org.
Chris
C I Twidle

Hi all

Thank you for your ideas.
I'll look into it asap, and let you know how things develope

rgds
Torben
Torben Olesen

Hello Torben,
I'm in the same trouble since few years, only in hot summer days..
Stage 2 engine.
But sometime no problem and sometime problem.
It probably depends on fuel.
Already installed a bespoke heatshield which covers much more than market parts. Covered this heatshield with a insulating sheet (ebay).
Insulating strip on the down pipe.
Insulating spacers on carbs (Burlen)
And recently insulating conduit on fuel line (no effect)

See my recent post :
https://mg-cars.org.uk/cgi-bin/or17?runprog=mgbbs&access=&mode=archiveth&subject=8&subjectar=8&thread=20200526201131200221

Of course see also the authors of the TTT2 articles and book website :
https://classicenginesmodernfuel.org.uk/Clubs/ModernFuel/Book.aspx?DYN_MENU_MainMenu=1000001&AspxAutoDetectCookieSupport=1

Winter fuel is more prone to boiling.

Another trick I'm thinking of as this seems to improve with time more that with sheilds !
Maybe the most volatile components of the blend evaporate with time and sun exposition of the tank. This volatile compound are not useful for our engines according to Paul Ireland.
Still no proof about that.I have to try. Cap open and direct sun for a few hours...With care of course.


Laurent.
LC Laurent31

No heatshield or spacers can prevent heat soak after a run with the car stopped..the entire engine bay and ALL of its contents reach the temperature that modern fuels boil. A Thermostatically controlled electric fan will work...OR just use the choke on start up and leave the choke on until you leave the store parking lot then push it off and you are good to go...your choice.

Regards,Tom
tm peterson

This thread was discussed between 22/06/2020 and 24/06/2020

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