400 carbs heating

[Hydroglen]

Thanks Des and Geoff.
Ok... carb setting and fuel pressure. Presumably you imply I am little on
the lean side...but the engine runs cool. Well Re the pump...I can't get it
started because the fuel has evaporated! Still, even with more fuel
pressure, it does not explain the very hot carbs. >
I will check both things. We are heading in to winter here in Canada, so may
not get a chance to try untill the warmer temp. return.
Cheers
Dorien

[Geoff Dowdle]

Dorien,



I dont believe the carbs will get hot enough to vapourise the fuel , even
"down under " on the hottest day .
If the carbs are set too lean you will have lack of power , possible
coughing /spitting . If they are STD needles my guess is it runs too rich ,
as the jetting is set for pool petrol in the late 40's which was about 85
octane . You are probably now using 92 - 98 octane . What fuel consumption
do you get on a trip, if tuned correctly it should be between 26 - 30 mpg at
60 - 70mph. 400's on BOCA economy runs in the past have got up to 35mpg.
Even my D2 engine could acheive 28mpg.


Get the use of a mobile gas analyser and find out if it is lean?
The float level of the front starter carb has the fuel level set too low
when you follow the workshop manual .(the level is about 3/8 in lower than
the others)
I usually bend the fork up to almost straight to raise the level the same
as the centre & rear carb.
I believe the front float was designed for a side draft SU.


To open the bonnets will only make a very little difference to the temp of
the carbs or fuel .


Regards
Geoff

[Hydroglen]

Geoff,
I get about 22 to 25 on a run doing 60mph but then I am a little heavy
footed. The car runs well and is very smooth. I use 87 to 90 octane, never
higher.
No I don't have access to a gas analyzer, but going by plug colour I am ok.
Well as I said.... after sitting the carbs are so hot I can't touch them for
more than a few seconds. That would certainly boil off the fuel. Leaving one
side panel up on the bonnett solves the problem.
Cheers
Dorien

[Bellerophon]

Dorien, something does not add up here, if you say that the car runs cool
and yet after standing with the engine switched off you are unable to place
your hand on the carburetors.
I take it that you have an original water pump with no thermostat so that
the water circulation with the engine stopped reverts to thermo-syphon. If
this is the case then there is something which is preventing the water from
circulating, because no way should the carburetor become too hot to touch.
If it was my car I would do two things before anything else, first remove
the water pump and check that all is well, second remove the radiator and
flush it out. This if it does not reveal a problem, then it will eliminate
possible problems in this area. If this fails then further avenues can be
considered, but do you have the SU or Solex carburetors and is the internal
oil cooler fitted.
My regards and good luck,
Bellerophon

[Hydroglen]

Well...I would agree with things not adding up.
The carbs are ok with the engine running. It is after some 10 minutes or
more with the engine off, that you feel the heat in the carbs. So once the
water stops circulating and cooling, the fires of Hell come in to play and
it all starts perking away!
Original SU carbs. I rebuilt the water pump a couple of years ago, however,
I had the same problem with the carbs even when in the UK. When I did the
pump I also redid the rad and that was pretty much plugged up. The car had
started overheating and so because both had to come off, both were done.
After your suggestion of checking the head last year or so, I took the end
plates off (no fun there) and pressure washed the head as much as I could.
When I say the car runs cool I mean about 85 as read on the gauge, with oil
around the same although the oil does get hotter at times. Not unusual and
very much like my 6C Alfa.
What internal cooler are you referring to? I guess by my question I am
ignorant on that one.
So it would seem I have covered your points, so now the ...further
avenues....
Since by opening the bonnett I solve the problem, is the exhaust manifold an
issue? It does not appear to be hotter than say other comparable cars I have
but maybe I should do a comparison.
I have a Pyrometer and tempelsticks for measuring hot surfaces, so I could
give it a try. If it was much hotter, I would then be asking myself ...WHY?
I had checked my tappet clearence some time ago and no news there as far as
I remember, but then again I may be forgetting. Age plays a part but I know
what I had for breakfast yesterday.... LOL.
Might be worth doing again and erring on the loose side?
O course now that we are down to an outside temp. of some 8c 45F the test
may not be as significant.
What do you think?
Regards,
Dorien

[Bellerophon]

Well now Dorien, as you assure us that the cooling system is on the top
line, and I presume that you have the correct gaskets fitted between the
head and the carburetors, then there is another reason for this problem. If it
was a known fault with the 400 then other members would be reporting the
same thing, however, there is not an outcry from other members.
So, you say that you use a very low grade petrol, this could be slow
burning and building up a massive heat sink in your manifolds which then causes
heat to rise to your carburetors. I have seen certain other cars running at
night with their manifolds glowing, so there are two things to try, first
change your petrol to a higher octane one and second check that you are not
running with retarded ignition. You did say it was running very smooth
which leads one to think it could be retarded, we will wait and see.
Good luck, my regards,
Bellerophon

[Hydroglen]

Thank you. Yes I realize that I am the only one or one of few with this
problem....I love rarity!
Ok, a good point on the fuel... I have used under 90 octane as I figured
petrol in England was not the greatest in the 40's and also why a manual
ignition overide was fitted. I can upgrade to a higher octane and worth a
try.

When I say running smooth, I don't mean retarded. If I advance more then I
go off timing and a slight roughness comes in without the pinging that you
would get on higher compression engines, when the timing is too advanced.

What are the correct carb gaskets? Mine seem very thin and why I wanted to
put thicker ones on, unfortunately the studs and nuts are flush so I can't
increase the space much. If you give me a direct e-mail I can send you some
pictures.
Of interest, I had talked about oil leaks ( a year or so ago) and you kindly
gave me some pointers. They were things that I had already done, so other
than your kind confirmation nothing new. I did find, however, that I get oil
seepage coming up from the 2 right forward engine studs. This then messes up
the head and eventually down the side.
Possible link to the carb problem? I doubt it, but thought I should mention
it.

Cheers,
Dorien