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tuning vc carby

how do you lean the fuel mixture on the stocko carby? as my car is running extremely rich. how do you tune it?

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Hey Mate,
If you are running on the old petrol and you are using LEAD REPLACEMENT PETROL, it will always run rich. You can watch the petrol go out of the exhaust sometimes when you go to start. LRP is unleaded with a cheap additive. Where you would be better using a good unleaded and buying your own additive. Mine was the same and i ran one shot for the first 50 litres to clean everything out, and then ran a upper lube oil that you mix with your petrol, the one i use does 600litres of fuel you get it from your local speed shop, and you will notice the difference even my tail pipe went back to a greyer colour than always being black. Or you can run a kit that keeps the lube up to you motor by drip feed. If you have already done this turn your mixture screw in slowly until it is running rough then turn it back out approx 1-1&1/2 turns until the motor is running smooth and when you rev it there is no flat spot.
Hope this helps,
Spider

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it is a stromberg, and i cant find where the mixture screw is

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the old original manuals are a must really, too many questions can be answered with a copy. I have not seen an aftermarket manual which does have the same detail ever. Original manuals are under $40 if you buy right,( the ones without the front and back covers are cheaper )....a bit more if you want a nice one.

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Hi Spider..

I just noted a few anomalies in your suggestions and I thought I should add to your comments.

Firstly, the fluid you see running from the exhaust when you start up is most likely to be water not petrol. When your car starts you will notice a 'steam' emitting from the exhaust while it warms up on a cool day. That is water condensing when it reaches the cold air outside the exhaust. Some LRP blends contain etanol. Ethanol is an alcohol. Alcohol and water blend and thus any water in your fuel will blend with the ethanol. Also the air that enters your engine through the intake contains some water too. When the fuel burns in your engine any water that has been absorbed will be ehausted as steam. The fuel you are using may have ethanol blended as an anti knock agent.

Secondly, the grey pipe we all used to see is actually lead oxide, a by product from the tetraethyl lead that was previously used as an anti knock agent in super petrol. The lead oxide also lubricated the valve seats. LRP does not produce a grey pipe but this doesn't mean something is wrong. LRP has been designed to both control knock and lubricate the valve seats without the health problems associated with lead oxide.

A properly tuned car should run well on LRP. In fact the octane rating of LRP is higher than super was. It is not just ULP with a cheap additive.

ULP: 89-92 octane.
LRP: 94-96 octane.
PULP: 96-98 octane.

All petrol types are blends of numerous hydrocarbon solvents and various other chemicals to produce a clean burning reliable fuel.

Some of the products that are currently used to increase the octane rating in place of tetraethyl lead are ethanol, toluene, benzine and methyl tertiary-butyl ether (MTBE).

Poida

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Hi Poida,
What i meant to say was the smoke not the actuall liquid. The car has never been the same, since this petrol came in. And yes it has been retuned, I changed to different heat range plugs tried everything. The car still idled like a pig. The motor is a 202 black engine. I was getting 15 mpg before i started to put in a additive on top of the LRP, now i am getting around 20-22 mpg, and the pipe is not as black as before it has changed to a lighter colour and is idling better. When i was running LRP it would ping and knock its head off going up a hill, but does not now.
I guess some may not know that petrol has a monthly volatility specification. That is, at the start of a new month, the maximum vapour pressure of petrol changes. Each month as summer approaches, the maximum vapour pressure of petrol reduces as the risk of vapour lock in carburetted systems increases. As winter approaches, the vapour pressure goes up as the vapour lock issue subsides and the need for more light-ends in the fuel for cold starting increases. There are probably 15 zones around Australia that have a different vapour pressure for EACH month of the year. Add to that the ups and downs of refinery operation where the petrol may not be maximised to the vapour pressure limit (usually is though for economics) and you further increase the permutations.

So, if you try and use petrol you bought in Jan in Sydney to run a lawnmower in Canberra the following June, you could well have problems starting it. Bear this in mind when laying up fuel supplies or storing the fuel for longer than a few weeks. It may not be the fuel itself, but the timing between when you bought it and used it that causes the problem. A similar issue occurs with diesel and "cloud point", or "cold filter plugging point". If you buy Summer diesel with a cloud point of 8 degC and try to use it in a vehicle in winter when the temp is around 5 degC , it may well go waxy & solid in the fuel lines or block your filters...farmers love this one at seeding time!!! Oil companies do make an honest attempt at fitness for purpose of a fuel (the ramifications are horrendous when it goes wrong, ask Mobil folks about Avgas!!), but the buyer/user has a responsibility in how the product is used as well. It can be a bit like using a flat blade screwdriver to undo a phillips head screw and blaming the tool when it doesn't work that well.
During the 70

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Because super (leaded) has been replaced with LRP you may find your car needs to be retuned.
The mixture adjustment on the Stromberg carburettor is not something that can be done without dissasembling the carby. There is however an adjustable screw that allows marginal changes to IDLE mixture setting. This does not change the overall mixture. It only has an effect while the carby is operating the idle circuit.
Changing the general mixture jet is not something I'd suggest you attempt. The jet has been chosen to operate correctly at the most suitable air to fuel ratio for the engine. LRP is produced to replace existing super fuel and should only require slight adjustment at tuneup from running super. You should not need to go as far as to alter jet settings.

Poida

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