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Old 23-11-21, 10:16 AM
Geoff Dowdle Geoff Dowdle is offline
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Join Date: Jul 2008
Location: Sydney, Australia
Posts: 406
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Glenn,
You have mentioned all the jetting sizes but what are the venturi sizes.
403 - 406 have 26mm ID
Most Bristol Sports engines , C,D,D2 have 28mm or 27mm
The size of the venturi determine the size of all other jets, then compression and other factors have a bearing as well.
The pilot jets #44 seem too small to me.
I have found over the years that many jets have been drilled out but they don't necessarily flow at the same rate as expected.
Do you have an inline filter between pump and carburettors as small particles can block or partially block the pilot jets.
Are the throttle bases all the same , most Bristols have two progression ports but other bases from Standard Vanguard, Landrover, Jaguar etc mostly have 3 or 4 progression ports .
Have the float levels been accurately checked, I have found an external sight tube from the main jet holder is the only way to do it accurately. Replacement carburettor tops are often machined differently where the needle valve is fitted, for different applications . Fitting a new needle valve with the standard 1mm washer can give quite different float levels depending the machining of the top.
I suggest you start the tuning process with three #10 emulsion tubes and have each carburettor jetted the same.
The emulsion tube holders can be different lengths which can raise the emulsion tube in relation to the float level , check the heights of the emulsion tube holders above the top of the main carburettor body, that they are all the same.
Remember you most likely have 70 year old carburettors that have been through many owners and so called "Carby Specialists" who have modified and exchanged parts from other carburettors which might not match the original part.
It might all sound a bit depressing but this is the accumulation of problems I have found in the past trying to get three Solex running together correctly, but on the other hand an original matched set in good condition mostly work very well and are easily tuned.

When you are happy you have a matched set in good condition take the car for a rolling road session to check the mixture through the rev range under load and calculate the ideal distributor advance curve needed. Then build that curve into the distributor .

Geoff
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