Has anyone used motorcycle carbs on a Rover V8 engine

hough

Road Burner
Points
67
From
Poole, England
Car
VW T5 swb 2.5tdi
Hey I'm asking this as iv seen it on an old custom car on Google, the engine is a Rover V8 3.5 auto but instead stead of twin su or a holley carb it is fitted with two banks of 4 carbs off a Honda cb750, which looks fantastic but what are the pros and cons of this and would it work ok on a standard engine and could I use smaller carbs?
 

HDi fun

TC ModFather
Points
637
From
Buckinghamshire UK
Car
Passat 2.0 TDi
I can imagine that it would be a bit of a handful to keep all eighty balanced. Carb per cylinder is unusual and can lead to poor fuel atomisation at light loads/low revs.

I learnt to drive on and could work on carb fed engines. I welcomed the eventual universal adoption of full multipoint injection. Far more reliable and far more economical with fuel.

I can see the appeal though ;) interesting proposition
 

T9 man

TC ModFather
Moderator
Points
1,137
From
London, UK
Car
Saab 9-3SS T9
I remember having twin SU's on my old Rover V8 and they were a nightmare. Forever having to check the top up level of the oil that they required. What was the best thing to use, 3 in 1 oil, engine oil, motorcycle oil? Lots of debate as to what was best, bottom line as HDi has pointed out - fuel injection! :)

But there is no getting away from the fact that a set of polished carbs on the engine looks gorgeous <B
 

HDi fun

TC ModFather
Points
637
From
Buckinghamshire UK
Car
Passat 2.0 TDi
I remember the SU carbs. had a 2.0 Montego with a single SU. BLMC Austin-Rover's technical guys worked hard to apply some electronic controls to it. It worked OK. I remember fondly the stupid little dashpot that had to be filled with 20w50 (so the manual says) oil. This served as a damping mechanism for the SU's variable venturi design. I never went for 3 in 1 oil as this has a vegetable component in it's make up which can set like glue as things heat up after then engine is turned off.

Os, do you remember the stupid tapered needle that needed to be cleaned up every few thousand miles?

My Dad had an Austin Ambassador 2.0 HLS with twin SUs. Yes, on a FOUR cylinder engine. That was a nightmare to calibrate as you state. If the airflow wasn't exact you'd have one pair of cylinders always dragging against the other pair. Hence about 22mpg. When it was working properly the fuel usage was just as bad - it was just too tempting to enjoy it for the the 5 minutes before re-tuning was again required.

Carbs are crude compared to multipoint EFi but there is an appeal to them that I miss. But probably only for as long as it took to sort them out every couple of weeks.
 

T9 man

TC ModFather
Moderator
Points
1,137
From
London, UK
Car
Saab 9-3SS T9
Os, do you remember the stupid tapered needle that needed to be cleaned up every few thousand miles?
I think so Paul, was that at the bottom of the carb behind a screw type cap? In those days I had to try and do all of the servicing/repairs myself, learnt the hard way on many things but to be honest with you; thankful for the lessons I learned.
 

HDi fun

TC ModFather
Points
637
From
Buckinghamshire UK
Car
Passat 2.0 TDi
I think so Paul, was that at the bottom of the carb behind a screw type cap? In those days I had to try and do all of the servicing/repairs myself, learnt the hard way on many things but to be honest with you; thankful for the lessons I learned.
With my 2.0 carb fed Montego: to get to it you had to remove the upper aluminium metric tit shaped assembly after removing the black topped screw on lid. There was a piston inside this to which was attached a needle which controlled the size of the fuel jet orifice. The base position of the jet itself was adjustable for height. Needles of different diameter and taper were used to allow the same SU carburettor to be deployed across many different engines.

AR's electronic setup used a stepper motor to control bypass air for cold start and the base position of the jet itself. AR also used a 12 volt operated vacuum switch - when the car was in gear and right foot completely lifted from the throttle pedal this reduced the vacuum in the part of the assembly above the piston which allowed the venturi to be smaller and the tapered needle further engaged with the jet base, thus reducing fuel usage as a result of better atomisation. Air flowing faster and a smaller jet base/needle orifice. It's all common sense in terms of fuel/air regulation but so much easier to achieve, and much more precisely with multi-point EFi.
 
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