
 Originally Posted by 
4bee
					 
				 
				Eventually LR did with the 2A a possibly earlier (JD would know for sure)  Just Teed in on suction & discharge lines.  It eliminated & bypassed the Mech Check Valves.
..........
			
		 
	 
 I think you have to appreciate automotive history to have an idea why brands went with particular ideas.
Today we think of a world market, with any innovation being available worldwide for the cost of a production licence as soon as it shows up, and designers and decision makers in, for example, Solihull, being well informed about what the opposition overseas is doing. But this has really only been the case since the 1960s. Before that there was no internet, there were virtually no international phone calls (yes, they existed, but were so expensive they were rarely used), and as a result, the NIH syndrome (not invented here) was much more dominant than it is now - and its still pretty strong!
The problem of getting fuel from the tank to the engine has been about sice the start of motoring. Up until the 1920s, the most common solution was to put the tank high (behind the dash or under the driver's seat) and the carbie low (updraft or sidedraft) or, on large cars, usually chauffeur driven, by pressurising the tank from the exhaust, with a hand pump for starting. By the late 1920s these were replaced by a vacuum tank on the firewall, that used manifold vacuum to do the job. 
Reliable and affordable mechanical or electric pumps did not appear until the 1930s (requiring the development of petrol resistant synthetic rubbers). The most successful and familiar mechanical pump came from the USA, and consequently had little immediate use outside the USA. It was, as far as I can remember, only adopted in the UK (during the war) by Austin, for their series of OHV engines that were a mirror copy of Chevrolet's design (without the benefit of a licence - but due to the small flow of information, GM apparently missed this). Other English manufacturers found the SU electric pump more suitable, being a direct replacement for the vacuum tank, and unlike the mechanical pump, did not require to be considered at the design stage for the engine (to make a mount on the block next to the camshaft and room for an eccentric on the camshaft). 
The Rover IOE engines were designed in 1939-40, although production was delayed until after the war, and no provision was made for a mechanical pump. However, by the time they were designing a replacement for these engines it was clear that a mechanical pump was the right thing to use, especially since the engine was initially designed as a diesel, and the SU pump was unable to supply either the pressure or volume needed for the CAV injection pump. But the six was the older design, so stuck with the SU.
From the designer's point of view, the mechanical pump is undesirable, and with  fuel injection systems usually requiring fuel pressure to start, is rapidly looking like vanishing.
				
			 
			
		 
			
				
			
			
				John
JDNSW
1986 110 County 3.9 diesel
1970 2a 109 2.25 petrol
			
			
		 
	
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