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Best fuel / additive to run a 1275GT? (10 replies)

Leep
7 years ago
Leep 7 years ago

Can anyone please help? Having not had an old Mini for some years, can I as which fuel and additive you all run your older, non-converted minis on? Do you use

Leep
7 years ago
Leep 7 years ago

Can anyone please help? Having not had an old Mini for some years, can I as which fuel and additive you all run your older, non-converted minis on? Do you use 'normal' unleaded or 'super'? And with which additive? Which is the best in your experience?

My car had been stood for 2 years, but when I got it going it ran like a dream. But, since topping it up with regular unleaded and the stated dose of Castrol Valvemaster it's started to run like a dog and is misfiring and back-firing. The car has't left the garage since I got it, so I'm assuming it must be releated to fuel I put in rather than another problem having developed.

Any thoughts or advice would be much appreciated.

cheers

Leep

LorraineLH
7 years ago
LorraineLH 7 years ago

I wonder if there's been some debris stirred up from the bottom of the fuel tank. Maybe fit an extra in-line fuel filter?

lwarrine
7 years ago
lwarrine 7 years ago

I run my daily driver (20vT) on Shell V power after advice from the guy that remapped it ...... on occasion I can't find a Shell garage and have to run on any other 'Super unleaded' then it just feel flat ... never appreciated the difference in fuels until experiencing this.

So based on that I run my old mini on Shell V Power with castrol valvemaster added.

Couple of notes;
As per above it is worth running a fuel filter or two (I run one at the tank end & one at the carbs end !).
Also it seems modern fuels can have a very limited shelf life & the fuel goes off ... again I was very sceptical of this but a friend that runs some old 2 stroke RD bikes found that his bikes wouldn't start .... turned out to be the fuel which had been left in the tank over winter. Drained the tank, fresh fuel & they fired up & run a treat ... upon draining the fuel it could be seen that it was 'cloudy' and not 'clear'. Suppose it's not such an issue with modern cars as they'll just change their ignition timing to try & compensate ... but seems older stuff may struggle.
Some fuel additives also contain a 'fuel presever' .... which seem to be readily available for things like lawnmowers as well .... so may be worth investigating.

ROLI
7 years ago
ROLI 7 years ago

Take the top off the bowls and clean the fuel in it. Look for any dirt in the bottom. Its all to do with water that forms in your petrol tank. My S has a compression of 10.75 so every 4th fill I fill it with Super unleaded (as Ive had the head modified toi run unleaded). Sometimes, to clean the carbs and valves I put in a full bottle of Wynns petrol booster from Halfords or MiniSpares. Good luck ! R

Andrew1967
7 years ago
Andrew1967 7 years ago

I run both of my Mini's, a '60 850 and a '64 1275 S powered Mk1 Mini with super unleaded fuel with no additives and they run much better on it than ordinary unleaded.

Neither have had their heads converted to unleaded and whilst they do not do many miles per year, both have done maybe 4000 miles since full rebuilds without any signs of valve seat recession. If anything the tappet clearances have got wider than tighter.

HOWEVER, whilst I have been lucky so far, I'm not saying there might not be a problem in the future but I'll deal with it if it arises.

Modern petrol goes stale very quickly but normally the addition of fresh fuel will get the car to both start and run properly. Have you checked the points and condenser (presuming its old school ignition) ?

ROLI
7 years ago
ROLI 7 years ago

Just had a horrible second thought....check your compression and if one is down you may find that a valve has burnt an edge , hence the backfiring...just a thought, hope Im wrong for your sake! R

Leep
7 years ago
Leep 7 years ago

[QUOTE=ROLI;n169339]Just had a horrible second thought....check your compression and if one is down you may find that a valve has burnt an edge , hence the backfiring...just a thought, hope Im wrong for your sake! R[/QUOTE] I really hope you're wrong too! But thanks for the suggestions, much appreciated. Cheers.

Leep
7 years ago
Leep 7 years ago

That's great - thanks a lot. Cheers. [QUOTE=Andrew1967;n169335]I run both of my Mini's, a '60 850 and a '64 1275 S powered Mk1 Mini with super unleaded fuel with no additives and they run much better on it than ordinary unleaded. Neither have had their heads converted to unleaded and whilst they do not do many miles per year, both have done maybe 4000 miles since full rebuilds without any signs of valve seat recession. If anything the tappet clearances have got wider than tighter. HOWEVER, whilst I have been lucky so far, I'm not saying there might not be a problem in the future but I'll deal with it if it arises. Modern petrol goes stale very quickly but normally the addition of fresh fuel will get the car to both start and run properly. Have you checked the points and condenser (presuming its old school ignition) ?[/QUOTE]

Leep
7 years ago
Leep 7 years ago

[QUOTE=lwarrine;n169321]I run my daily driver (20vT) on Shell V power after advice from the guy that remapped it ...... on occasion I can't find a Shell garage and have to run on any other 'Super unleaded' then it just feel flat ... never appreciated the difference in fuels until experiencing this. So based on that I run my old mini on Shell V Power with castrol valvemaster added. Couple of notes; As per above it is worth running a fuel filter or two (I run one at the tank end & one at the carbs end !). Also it seems modern fuels can have a very limited shelf life & the fuel goes off ... again I was very sceptical of this but a friend that runs some old 2 stroke RD bikes found that his bikes wouldn't start .... turned out to be the fuel which had been left in the tank over winter. Drained the tank, fresh fuel & they fired up & run a treat ... upon draining the fuel it could be seen that it was 'cloudy' and not 'clear'. Suppose it's not such an issue with modern cars as they'll just change their ignition timing to try & compensate ... but seems older stuff may struggle. Some fuel additives also contain a 'fuel presever' .... which seem to be readily available for things like lawnmowers as well .... so may be worth investigating.[/QUOTE] Thanks a lot, very much appreciated. I hadn't heard of modern petrol going stale and as the car had been stood for 18 months or more before I got I'm hoping this might be part of the trouble. Cheers.

Leep
7 years ago
Leep 7 years ago

[QUOTE=LorraineLH;n169315]I wonder if there's been some debris stirred up from the bottom of the fuel tank. Maybe fit an extra in-line fuel filter?[/QUOTE] Will give it a go. Many thanks.

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