flat spot

[seanwhite]

Hi there,

Looking for a bit of advice, my stag is suffering from a flat spot when first accelerating and then with any small application of the accelerator pedal. It feels like fuel starvation. It has the original stromberg carbs fitted which were overhauled last year. It has lumenation ignition with recent new plugs.

Thanks

[StagnJag]

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Hi Sean,

Do your dash pots have oil in them - ordinary engine oil. If they have nothing to damp the movement, or too thin an oil they will rise too quickly causing momentary fuel starvation.

(I think!)

I am sure someone will confirm or dismiss this shortly!

Rgds

Dave

[seanwhite]

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Thanks Dave off out to the garage to check now

[mattsay]

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Hi,

Did the flat spot arrive at the same time you fitted the new plugs?

Do you have a sports coil? If so what gap are you running? You might need up to 35 thou (virtually 0.9mm). Gap with points and standard coil is only 25 though (0.65 mm).

From what I have read, another possible cause for poor initial acceleration can be siezed (or diaphragm perished) on the vacuum advance on the dissy.

As the carbs were recon last year I would look eleswhere first, except checking the oil in the dampers.

Cheers.

[maverick]

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mattsay wrote:

Hi,

Did the flat spot arrive at the same time you fitted the new plugs?

Do you have a sports coil? If so what gap are you running? You might need up to 35 thou (virtually 0.9mm). Gap with points and standard coil is only 25 though (0.65 mm).

From what I have read, another possible cause for poor initial acceleration can be siezed (or diaphragm perished) on the vacuum advance on the dissy.

As the carbs were recon last year I would look eleswhere first, except checking the oil in the dampers.

Cheers.

Hi My car suffers from poor initial acceleration can be siezed (or diaphragm perished) on the vacuum advance on the dissy.
Are they easy 6o remove service and repair etc,?

Any help welcome,

Mark

[seanwhite]

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Topped up the dash pots, off for MOT in the morning so I will give it a road test on the way there.

It has a standard coil fittedI think, and the plug gaps were set to manufacturers spec.

Thanks for the pointers so far, I will also check out the diaphragm as well.

[Guest]

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Hi Sean ? It rather sounds as if you have one or more carb diaghrams failing, at about £3 apiece it's not worth not doing. Martin.

[seanwhite]

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Thanks Martin, they were replced with the overhaul kit, but I will check them again. The car was in storage for the last 9 months so I suppose they may have been affected.

Sean

[Guest]

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seanwhite wrote:

Thanks for the pointers so far, I will also check out the diaphragm as well.

Hi, to check the dizzy diaghram, pull the A & R pipe off at the carb end and suck, if you can maintain a vacuum it's OK. Martin.

[seanwhite]

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Sounds like a job for her indoors heh heh,

[Guest]

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seanwhite wrote:

Sounds like a job for her indoors heh heh,

I'll bet SWMBO didn't read this before you sent it ! Martin.

[seanwhite]

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Too right ! in fact she's not even in the house thats how brave I am !!!

[Guest]

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seanwhite wrote:

Too right ! in fact she's not even in the house thats how brave I am !!!

Typical Stag owner then. By the way, welcome to the second best place a Stag owner can be ! :dude: Martin.

[mattsay]

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If the car has been laid up for 9 months, the fuel may have gone off. Modern fuels have poor longevity. Is it old fuel still in the system? Might cause difficult starting too.

[seanwhite]

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Fresh fuel went in before the car was started, thanks for the suggestion though.

Speaking of which.. Anyone running leaded petrol in their cars?

I ran mine for a while a few years ago on Avgas, basically a nice high octane fuel used to be equivalent to the old 5 star fuel. Car went fantastically well