400 carbs heating

[Bellerophon]

Dorien, I do not think you can have oil seeping from the front studs, but
may be the cross tube, anyway send me a photo and I will see if it tells me
anything. _Pegasushunter@aol.com_ (mailto:Pegasushunter@aol.com)
Regards,
Bellerophon

[Bellerophon]

Dorien, I have just measured a new original gasket from Bristol Cars which
fits between the head and the carburetors, this is 0.060" or a 1/16" thick
new and this compresses down to approximately 0.40" or 1mm. once used.
Hope this is of help.
My regards,
Bellerophon

[Rubbond]

I can't follow this reasoning at all, Bellerophon.
Massive heat sinks? Glowing manifolds? (Do you mean inlet?).
If the engine is running well normally, and the car has a manual advance and
retard, I wouldn't have thought the fuel quality could be a major factor
contributing to overheating?
Fuel droplets travelling through the inlet manifold will have a cooling
effect as they evaporate.
When the engine is switched off the carburettors however obviously shouldn't
get so hot that you can't touch them.
I would have thought it much more likely to be a cooling problem.
The water temperature you see on the dashboard gauge is only the temperature
where the sensor is located.
Maybe some channels in the head are blocked (or even the head gasket is
missing some holes!) and there is no circulation at all near the
carburettors.
I have messed around with very old outboard engines, and overheating is
ALWAYS caused by blocked channels, some of which are almost impossible to
find.
Good luck!
Rubbond.

[Bellerophon]

Well Rubbond, The 2 litre Bristol engine does not have an inlet manifold,
it does have an inlet tract where the carburetors are bolted direct onto the
cylinder head.
All fuels are not the same and some burn at a slower rate than others, so
if you have one of these in your tank you can still have burning fuel
entering your exhaust manifold, and thus end up with a very hot manifold.

Modern fuels are only intended to stay in your tank 3 or 4 weeks maximum,
after that they start breaking down into their various parts (ethanol)
which can eat away at components such as the old type of petrol pump diaphragms.
If you have one of these change it to a modern resistant one or you may
suffer the same thing I did on my way to Scotland. Although my engine kept
running a hole developed in the diaphragm which allowed petrol to fill up my
sump and resulted in an engine rebuild.
My regards,
Bellerophon

[Hydroglen]

Correct ....and why I and others do not use car fuel in our planes.
Aviation fuel does NOT have ethanol and has preservatives for long term
storage and minimizing carburettor icing. The use of fuel with ethanol has
caused many aircraft engine failures/ problems. In Canada the only gas
station fuel without ethanol is Shell, All others have 10 to 16% ethanol.
Regards
Dorien

[Rubbond]

Dear Bellerophon,

Manifold, duct, tract, all the same idea I guess? One way or another, if you
have 6 cylinders and 3 carbs, you will have to split the flow somehow.
I don't think using the exhaust as a sort of afterburner however is a very
good idea. From a thermodynamic point of view it's best to burn all of the
fuel inside the cylinders.

As to the fuel pump diaphragm, neither the ethanol in a "modern fuel" as you
call it , nor all the other additives or the basic naphtha for that matter
should be eating away at it. NBR rubber was produced already before World
War II, and is pretty resistant to both gasoline and ethanol.
Or are you are refering to "sour gas", which can be formed in small amounts
in unleaded gasoline? The effect of these hydroperoxides however can be
compounded around. I hope you are not buying original 1950's stock
diaphragms?

If your fuel pump is also bolted straight onto the engine, which I suppose
it might be on a pre-war design, there are much better rubber types
available today. I have cut out diaphragms and gaskets in the past from a
piece of cured FKM sheeting and a pair of scissors. That will last forever.

A "modern fuel", or leaded fuel for that matter, certainly doesn't break
down into ethanol, although with time the most volatile fractions will
evaporate.
"Stale fuel" is just what's left after the lowest molecular weight fractions
have evaporated. This will result in delayed onset of ignition and slower
flame proagation.
It takes a very long time however for a can of petrol to burn like diesel
fuel. You can still blow your head off.
And anyway, it's too late now to put some aside thinking it will be
drinkable this Christmas.

This was all a bit tongue-in-cheek but largely based on sound facts (or was
my prof telling porkies?).

With best regards,
Rubbond.

[Rubbond]

I guess this then is because Ethanol is hygroscopic?
I'm going to look fairly stupid now having mentioned afterburners.....