Why did Stuart Turners make their own carb?

I was mulling this over on the Stinfo exchange, but they are passing unto history now so I thought I'd put it here too.
As Amals made carbs, they were almost certainly supplying a standard carb that was already in production and jetting & sliding it to suit the ST's performance curve.
ST's on the other hand must have had a good reason to go to the not inconsiderable trouble of designing & making a carb of their own. It was, after all, a pretty unusual thing to do!
Any thoughts gentlemen?
Regards,
Kim Siddorn
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I've no idea really other than maybe cost? But your question reminds me of the early Ford Escort Mk111. for some reason Ford decided to produce their own variable venturi carb for the thing, it was a dreadful disaster unlike the SU variable venturi (constant depression) carb. Many cars got a conventional Weber carb, available as a kit with all necessary odds and sods included, retrofitted which gave smoother running and better petrol consumption.
I fitted a few dozen IIRC!
Julian.
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Lots of crazy things (excessive insourcing, excessive outsourcing) look like they might make sense when you're dealing in Ford Escort volumes.
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kimsiddorn wrote:

Not quite so unusual when the basic design was evolved pre WWI, after which I think it was just a case of if it ain't broke don't fix it! A 'proper' carb was part of the transformation from P5 to P6, no doubt helping to wring out the extra pony or two and the late R series engines also sprouted an Amal probably on cost grounds.
NHH
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Nick,
I thought the P5 had the same Carbs as the P6, SU's. That's certainly what is fitted to my P6.
Martin P

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arf arf. Roland

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