hi, have a 68 mini deluxe 1000cc with a dellorto set up at the moment. have recently started working at 5:00 in the morning. so therefore pretty cold , the carb was recently tuned before winter started. Past three mornings she starts fine... idles fine... after a few minutes of driving tends to cough a bit and feels like when u start to run out of fuel. the car doesnt die whilst driving but is noticablly . When pull over to sus it out or park... she why die. will start fine again... and gets me to work with encouragement and coughing a fair bit more on the way ... thankfully works only 10 - 15 mins away. when i leave work later on wheather it be at 8:00 or 12:00 this does not occur and is like she always has been... solid as.
i am just a bit confused as to what is going on and would appreciate any responces that may shed some light.

Well, I do know petrol has a real tendancy to expand and contract with temp changes, but, still , the feul pump deals in quanity not density. Having said that, it may affect the fuel float in the carby, maybe it sits higher in the fuel bowl in cold dense petrol, thus cutting off replenishment..Don't know, Just a thought.

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It's been 19Yrs in the Making.....Last Rego sticker 6/89

But SOON, VERY SOON

Also think abut the venturies icing up restricting.

You will here quite a bit about that now the rain bits have passed us by and the cold frosty nights have come. I know thats not Brisbane normally but.... Throw a cover over the motor overnight and then let it warm properly before you drive off and see if it still happens - remove the cover from the motor before you start it though.

Stupid question but, are you allowing her to warm up properly in the morning?

My S will refuse to cooperate properly if i don't leave her to warm up until the needle has atleast moved up to above the cold mark.

My wife's 1293 uses the same `twin SU technology'....
Geez I'm glad in Winter my daily driver 1360 Mini runs a Dellorto... I start it, drive 200 metres, then push the choke in.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Definitely sounds like the carb is icing up.
Don't expect to see chunks of ice and frost on the outside of the carb (like some kind of "Back to the Future time travel sequence), its very small, near microscopic pieces of ice forming in the venturi.

It has to do with the air speeding up through the venturi, resulting in a localised drop in pressure, and a corresponding drop in air temperature, as well as a drop in temperature of the air due to the evaporation of the fuel vapour into the air fuel mix. The air always has water vapour in it, and a drop in temperature will cause some of it to condense out (and in this case freeze into ice).

The ice can disrupt the flow of the air fuel mix through the carb, though only to a very limited extent. The biggest problem is that the ice "takes up room" in the air fuel mix which could otherwise have fuel in it. This leads to a weak mixture, which causes a lack of power, and stalling when idling.

How to solve the problem?
The only real way is to get heat into the carby.
This can be done by warming the engine up first, by using a water heated manifold, and by parking the car somewhere warm overnight.

I use a VW Beetle as my daily driver, so I know all about the problems of the carb icing up (no water heated manifold of course, and long runners from the car to the inlet ports mean the carby takes an awfully long time to get warm on a cold, frosty morning).
Some VW drivers swear by an electric heating element you can buy that goes between the carb and the manifold - never tried one myself.
Maybe one of the mad scientists on this forum could adapt one of these?
Probably not necessary with a water heated manifold.

Cheers,
Ray.

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68 Morris Minimatic - Blue/White


29 Chev tourer
31 A Coupe
63 Anglia
63 VW Beetle
69 VW Beetle convertible
89 Daihatsu Charade
03 Mitsubishi Mirage
07 Nissan Micra

I have the same problem.

I always thought it was ice in the carb . I let my car warm up and I don't get that problem you described. Good suggestion of the water heated inlet, my mechanic suggested that also. My carbs sometimes make a "loud tingle" sound but only once when cold. <- imagine if ice was blocking the fuel flow and that would be what you get when the pressure builds up, increasing the temp and melting the ice all locally in the carb - with this imagination you will hopefully understand the sound I am describing and agree that my problem is icing on the venturi.

All I need is a house with a shed.

Edit: - I am running on twin SU 1.25"

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Spritey!
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Lower your standards. Increase your success rate.

A shed is not necessarilly going to stop the carby icing. Its that frosty morning first couple of kilometres on a cold engine.

I drove 30 kms this morning from my house to the Mudgee Smalls farms Field Days site. It was seven clicks before the water heated manifold kicked in and at the end of the thirty clicks in the neddles was still just creeping up over the cold mark.

Mind you, you cant have it both ways. Mine has an oil cooler and a big "tropical" (morris 1100S) radiator and while its beaut in summer it certainly is super efficient in sub zero early morning temperatures.

The organisers of the MSFFD wanted all display cars in by 0800 hrs, well before the general public.

The same thing used to happen to me when driving between Melbourne and Ballarat. I had a single 1.75" Su on a non heated mainifold. Didnt matter how long you'd been driving, but when you got to the Gordon area there was a dramatic loss in power. Got past that "bit" and all was good again.

I had an oil cooler and really good radiator on a previous clubman I used in Goulburn , down there I had a cover that slipped over the oil cooler and also blocked about 40% of the grille area , just the thing to reduce airflow and keep the heat in to start with .

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