Ive found that with a single su carb on a water heated manifold on my 1310cc rossa
that an 88 degree thermostat is best for winter
and an 82 degree thermostat is best for summer.

a cooler thermostat is too cool and the engine gives less power, torque and economy.

what do other rossa drivers think??

i think unleaded petrol needs to be warmer than leaded.

after driving around my hif44 gets very cold even though its on an aluminium manifold with an aluminium spacer and special
home made aluminium foil gaskets. water heated manifold of course.

my nelly gives the best power the seconds AFTER ive stopped for a few minutes and the carb gets warm.
im convinced this is to do with heat in the petrol and nothing else.

after a few seconds the carb cools down again and the lovely power is gone.

this may seem like a crazy post but ive been watching this weird issue for years and want a warmer carb
HOW DO I GET A WARMER CARB? so i can keep the amazing power that i get after a short stop.



i do the weird posts so you dont have to.

all cars are fuel injected now.
so shell have optimised Vpower for injection. . .. . .
im sure V power unleaded needs a WARM carb but a cool engine to give best torque.

i may be in a club of one with this issue but im gonna stick with it until ive got a warm carb and a cool engine at the same time.
so when i post that ive blown the gearbox - you will know that ive succeeded in my crazy quest. .. .

The ally inlet manifold probably isn't helping - it radiates heat very well so all the surface area is losing any heat that it might have picked up from being in contact from the engine. If you want to keep it in - try wrapping the manifold. You could try wrapping the carb too to an extent if you are careful not to obstruct any linkages - very careful because any obstructions/friction will generally be overcome by your foot on the pedal but not by the relatively weak return springs and having a throttle jam wide open is an interesting experience to say the least.

Failing that..... Do you have a heater? Could the heater pipe be routed round or near the carb? Maybe a coil of copper around the carb held in place with a bracket.

Box the carb in to keep warm air around it rather than allowing it to dissipate into the larger volume in the engine bay. Keep the bottom of the box open to allow warm air rising from the exhaust to surround the carb but capture it to prevent it from just carrying on past is the theory. Not sure how turbulent the area around the carb is when the car is in motion though so this might be a non-starter.

If it's only the fuel you are trying to warm then what about a coil of microbore pipe around a coolant hose and run the fuel through that before it gets to the carb?

All just possibilities that come to mind - the practicalities may discount some of them and there's the problem of keeping it at the sweet spot and not going beyond it and getting the whole thing too hot in use.

Iain

hey Iain! many thanks for the reply!

ive taken onboard all you said.


a gtm rossa is different from other transverse engined cars in that the area round the carb is open to the air
so when you are driving along that area is cold. or at least colder than other a series cars that have a bonnet.

ive spent some days beavering away.
made two gaskets out of 0.3mm copper and used them instead of the normal paper ones.
dispensed with the carb spacer.
so now my hif44 is bolted to the minispares water heated inlet manifold with just two copper gaskets and the
metal abuttment plate that holds the throttle and choke.
there was a LOT of fettling involved as the throttle linkage fouled on the manifold.
i had to buy new studs as the old one were too long.
so the heat "flow" from the manifold to the carby is much better.
cos ive dispensed with paper gaskets that dont transfer heat and ive shortened the heat path,.

enough of this chatter.

IF YOU ARE DRIVING A GTM ROSSA THEN YOUR CARBY IS PROBABLY TOO COLD
at least for ten months of the year it is.
fit an 88 degreee thermostat and do my mod - you wont be dissappointed.
my nelly runs MUCH better with a warm carb - more torque -more power - more economy.

if we have a heatwave then i will change for an 82 degree thermo or even a 74
the point is by linking the carby to the manifold with a short heat flow
IM IN CONTROL of the carby temp. NOT THE WEATHER.

how cold is too cold??
drive your GTM for at least 7 miles on an A road or motorway
park up and feel the top of the carby - if its not at human hand temp then its too cold.

got rid of all the gaskets that are between the carby and the inlet manifold.
replaced the steel thing that holds the choke and accelerator cable with a home made one made
from 3mm thick copper.
this maximises the heat that gets into the carby.
it works - my hif44 is a LOT warmer.

my nelly definitely runs better.
however in my experience shell Vpower is different from other petrols and definitely likes a warm carby.
so if your running regular petrol then this warm carby obsession that i have my not suit your car.

i have to run v power cos of relatively short cam (kent 256) and high compression.

regards to everyone.

forgot to add that its 12 centigrade in manchester today.
i would really like a hot day eg 20 centigrade or more to find out
if i have gone overboard with carb heating.
but certainly from minus 2 up to plus 12 this warm carb seems to be right for my car
remember i have a 5 inch ram pipe drawing air from the boot.

.As a retired AA patrol I came across a common fault when cars had carbs.....Petrol is a spirit,so the high speed air flowing through the carb would become chilled.Ice would form in the orifice making it narrower.This reduced the airflow creating a richer mixture.Eventually the car would stop due to flooding.However,whilst the driver was wondering what was wrong,the ice would evaporate due to the heat of the engine.With difficulty it would restart and seem perfectly ok for a few more miles,until.....you guessed it.All the fault was ,was that the warm air pipe from around the exhaust had come adrift!Now you know why Minis had big air cleaners with a bi-metalic airflap to add warmer air in the winter.UNDER NO CIRCUMSTANCES must you try to warm the carb in any way!!!The black plastic spacer is important.The manifold hotspot or water heating is to aid vapourisation,not to HEAT the carb which should remain cool.The people who designed engines knew what they were doing.If the carb needed a heater ,they would have put one on it!Many people change the air cleaner for something like a K&N which is ok in the summer,but can be problematical in the colder weather.So a warm air feed is what's required.

I don't wish to put anyone down,but if you don't have the technical knowledge to solve a problem,them don't offer a solution which may be dangerous.We are talking about petrol here.UNDER NO CIRCUMSTANCES must petrol be warmed or heated before entering the carb.Nor must the carb be heated,only the manifold and the air entering the filter.

This is very interesting and not what I expected.
So I don't quite know how to proceed with this thread.

I stand by what I said : my carb was running too cold to get an effective mixture.
even in this recent hot weather.
Its not any more and my GTM is running better than it ever has by a considerable margin.
better torque better power better economy.
I maintain that you need to get your carb to certain temp to get the best mixture of fuel vapour and droplets.
and in my experience on my car with various thermostats you cannot get this right with manifold heat alone not with v power petrol on my car anyway.
anyone who is interested can get me on
dastardlyman@gmail.com

the last thing I want to do is cause a controversy!
best wishes
Peter Dickson
ps vizard latest book (2010) about American v8s is well worth a read - he speculates that you need to get 15% of the fuel as vapour (not droplets) for best power. I think ive achieved that or something like it. remember the airstream is at 100mph or thereabouts in the inlet tract so there is not a lot of time to get the temp you need.

In for a penny, in for a pound.

Do you run a mini or a spridget or any other carbed car with a "standard" bonnet?
if yes this is not relevant to you.

Do you run a GTM with a Big slit in the boot above the carb?
you do? read on.
Do you run a long ram pipe that draws air from behind the engine compartment?
yes? read on.
do you run a short cam with high compression and have to use V power petrol?
yes? good good.
did you realise that the GTM fuel pipe runs through the "transmission" tunnel near the
hot water pipes?
yes? good.
did you decide to run your petrol pipes through the passenger compartment because warming
up the petrol seemed a really daft idea?
yes? good.
after many years of fiddling about did it dawn on you that your carb may be running too cool?
yes? (and that moving the fuel pipe to make it cooler was folly in the first place?)
does your GTM have "NACA" ducts on the boot as well as the big slit?
yes?

so what follows is probably relevant to no-one except me and my little nelly.

Bit of background here.
Ive used "A" series engined cars as daily drivers since 1989 and got a degree in chemical engineering.
ive done about 6 engine out rebuilds.
While my posts here may seem a bit flippant and cheeful, I only make them
because ive got something useful to say.

Ive got copies of:
how to modify your mini by david vizard from 1974
tuning BLs a series engine 1st edition and 3rd edition (vizard again)
how to build horsepower (2010 by vizard again a great book)
the 1275cc A series high performance manual by des hamill.
4 stroke engine tuning by graham bell
mini performance manual by tim mundy
there is some great stuff out there on the web (and some rubbish too)

took my 998 mkII mini to rome in 1989
had a mark 1 mini with a 1071 engine as a daily driver from 1991 till 2000
used my nelly (GTM rossa MK2) as a daily driver on and off since 2000
run various camshafts like 266, 256 , kent 600 and the old 544 cam.
i prevented carbs icing on 1071 by running copper pipe full of hot water round them
very successfully
if you have a 1071 put a 544 cam in it - they are a marriage made in heaven.

When i got nelly she had an oselli rally spec engine with an aluminium carb spacer
not a phenolic one.
as for not heating carbs ever - try telling that to kawasaki.

so whats all this about?
i live about 1 mile from the nearest shell garage and i would drive there (engine from cold), fill up
pay (obviously) and then drive off. there would then always be a "magic" 1/4 mile where
nelly pulled like a train. it would be like she had an extra cylinder.
and before anyone says your dashpot oil is wrong or your timing is out - no they are not.
if you drive around in your gtm then stop and feel the carb it will be cold - really cold.
if your carb feels warm then again this is NOT relevant to you and your cars specification is way different to mine.
i came to the conclusion that the "magic" 1/4 was because there was heat soaking into my carb while it was parked
at the garage for the five mins it took to fill up and pay. this warm carb is what you need with V power petrol.


im going to be VERY specific here.
1. Unleaded petrol is not the same as leaded petrol and is developed for fuel injection - not carbs.
and v power is different from other unleaded petrol.
2. the GTM rossa has a hole on the bodywork above the carb - making it pretty unique,
so the "underbonnet" temps that you get in a mini or a sprite dont happen at the back of a GTM rossa.
3. I run a 5 inch ram pipe that draws from the luggage space behind the engine and it works very well.
4. I absolutely positivily do not race my GTM ever.
5. there is precious little info on this - why would there be? - all cars have fuel injection.

so what i am suggesting is VERY specific to a GTM rossa running unleaded petrol.
not a mini or any car with a hot air area round the carb.
in fact since my car draws air from BEHIND the engine area this probably means my car is unique
in that it is drawing colder air than other rossas.
I run 1310cc & V power exclusively and currently have a 256 cam timed at 103 degrees very rarely go above 4500 rpm.

OK, with all that said. here is the proposition:
you need to get a certain amount of the fuel as vapour for great torque, lets say its 15% vapour
the other 85% is droplets. It doesnt matter what the actual proportions are just that you have got to get this
proportion right for good torque.
For some reason that im not clear on you MUST get this done at the carb.
So a warm carb being fed cold air is much better than a cold carb being fed cold air that subsequently gets to the
magic 15% / 85% in the manifold area.

I currently run :
1. a minispares water heated manifold and an 82 degree thermostat
2. no carb heat shield
3. no carb spacer no gaskets and my own copper abuttment plate accelerator / choke flange thing.
3. coiled up copper pipe round the single hif 44 to get more heat into the carb from the hot water system
i moderate the heat going into the carb using wood between the coil and the carb.
i guess the water in the copper pipes is at 70 degrees centigrade cos its been through the heater and inlet manifold already.


i now drive around all the time in the "magic" zone. I like it a lot.

you can view the specs of petrol such as its boiling point online
(it is composed of different "fractions" so boiling point is the wrong word) and my warm carb is not dangerous.

Ive put this information up for interest only - i dont recommend anyone does what ive detailed here.