Weber 45 DCOE 9 Conversion Data (Factory)

#1
From a Rover Association of North America newsletter, issued in early '72. Probably the only factory data known for converting a TC to Weber carburetors. Thought I'd share this if anyone is contemplating the idea of converting his or her TC from SU to Weber!

A Weber-conversion for the TC:

For those 2000TC owners with time on their hands and adventure in their spirit they might consider scrapping the-SU's on their TC and installing a set of Weber carburettors. As you might already know there was a small amount of development work carried out on this before the TC was introduced in 1966. The factory experimented with Weber carburetors on cars which had the standard TC camshaft as well as one with a modified camshaft! The factory informs us that the Webers didn't increase the maximum, horsepower significantly although they did improve the middle-range performance. In questioning the factory regarding the recommended specifications for such a set-up they indicated that it would be best to retain the stock TC camshaft. Mr. E.W. Wright, the Executive Engineer for Engines and Transmissions at Rover, specified the following data for anyone considering such a conversion:

Weber carburetors with TC camshaft:

Type: 45DC0E 9
Choke size: -40mm
Main jet: - 185
Air jet: -210
Emulsion-Tube: - F ll
Auxiliary venturi: - 3,5
Pilot slow running jet: - 60 F2
Pump accelerator: - 50
Float chamber-needle and seating: -200 spring type
Float level;setting: - 5.0mm

The carburettors were connected to the cylinder head via 4 short pipes mounted flexibly onto a manifold. An air plenum chamber without air filter was used by the factory, although it seems-that ram tubes or the small air cleaners specifically designed for Webers could be used, without difficulty..
 
#3
christopher storey said:
Is that emulsion tube meant to read F11 ? it comes out on my screen as F ll
I'm sure it would be F11, which I'm quite sure is a proper Weber number for a DCOE. Weber emulsion tubes are a black art, no rhyme or reason to the numbering scheme.

Yours
Vern
 
#4
interesting : F11 was certainly used on the Lotus Ford 1558cc, but was not used commonly on anything but Fords . It did, according to Passini's book find favour with engines with strong vibrations and/or high compression , so maybe this was why it was chosen.
 
#5
It seems that from the start Rover were committed to overwhelming the TC with massive carbs.
The power output was up by 25% over the basic 2000 engine which looked good, but flexibility is constrained.
The HD8 SUs were just too big (when they upped the capacity by 10% in the 2200TC they reduced the carb size and produced a more responsive motor)
and a pair of 45 DCOEs are a big bite for a very ordinary 8 valve 2 litre.
But what I would like to have seen is how they managed any air filters - there's barely space for the filter box alongside the inner wing on the SU set up and Webers are distinctly deeper, even without any trumpets. Are there any pics or drawings surviving?
 

sdibbers

Well-Known Member
#6
Andries said:
The carburettors were connected to the cylinder head via 4 short pipes mounted flexibly onto a manifold. An air plenum chamber without air filter was used by the factory, although it seems-that ram tubes or the small air cleaners specifically designed for Webers could be used, without difficulty.. [/i]
Looks like they didn't bother with a filter (I would be so worried with that setup). I wonder if the four short pipes were in fact a new manifold? Although they mention them being fitted to the manifold. The openings must have been right up against the inner wing! Unless they had a cut out/bump out into the wheel well space.

I totally agree about being over carb'd. I've just found a pair of HIF6's to replace the HS8s on my 2000TC that I've bored out to a 2200. I'm looking forward to feeling the difference.
 

sdibbers

Well-Known Member
#7
I found a quote on a page for a tuning company about why Rover chose the HS8's From a chap called Chris Logue

"Daniel, You have been misinformed re the carbs. The 2 litre twin carb (TC) had 2″ carbs as standard. The 2.2 litre had 1.75″ carbs. The 2 litre didn’t need 2″ ones, but the damping on the 1.75″ ones wasn’t man enough to prevent the pistons from pulsing themselves closed. By the time the 2.2litre came out, the 1.75″ damping had been improved so they used those. I was told this by Jack Swaine the Rover development engineer who designed the engine."

See more at: http://www.cckhistoric.com/rover-p6-200 ... /#comments
 

Demetris

Well-Known Member
#8
I can't really see the connection. :?
The damping of the pistons in the SUs is something very simple and very adjustable, even for the home mechanic, never mind the motor industry! :roll:
 
#9
Despite Demetris's doubts, there may be something in what was said, although the actual substance of it sounds as though it has been the victim of Chinese whispers. There have on occasion been difficulties with resonance effects in 1.75 inch SUs. For a while, it was the fashion with tuners of Minis to substitute a single 1.75 SU for the twin Sus used on Coopers and Cooper S cars, but it became very difficult to find a spring which did not produce flutter of the piston. It was nothing to do with damping, which is a separate issue, but was connected with the natural frequency of the spring compared with that of the airflow at certain load/speed combinations. Maybe something similar occurred with the P6
 

sdibbers

Well-Known Member
#10
To be honest, it was a random comment I found when trying to google webers on P6's. The fluttering is something I hadn't encountered on SUs and it made sense in some ways. I agree with Demitrius that it seems a small thing to nix using 1-3/4" carbs because if it. The spring comment makes some sense too. If it's more of a harmonics issue I can see that being tough to cure.
 

Demetris

Well-Known Member
#11
christopher storey said:
It was nothing to do with damping, which is a separate issue, but was connected with the natural frequency of the spring compared with that of the airflow at certain load/speed combinations. Maybe something similar occurred with the P6
This one sounds more reasonable to me.
Thanks for the explanation.
 
#12
It is my recollection that the TC I owned in 1975 FXC 201C was the fastest of all I owned , this had 2 inch carbs and most importantly it was designed to use 5 star leaded fuel ( ie 101 octane) and the compression ratio were 10.5 to 1.

These were really fun to drive and would rev to about 6750.

Then all the fun was stopped by the emsission controls that came into the states and yes the invention of fuel economy. Up to about 1975 no-one worried about mpg .

So the carbs were changed to the 1.75 and the engine detuned effectively. Therefore the increase in capacity to 2.2 to maintain torque and output for a slightly heavier car.

As regards fitting Webers , yes this was done at experimental , but the closeness of SU at Wood Lane with Rover and the SU reliablility was
deemed more important than the mearge increase in power amd lower mpg that would result. The later TC's were then competing with the V8 whith the mpg differential not that great.

As I own a TC would i fit twin choke webers . Probably no , as Alfa do it better.
 
#13
I used to own Alfas and it's pretty odd that Rover was using 45DCOEs on this engine. You can make 150hp+ on an Alfa motor on 40DCOE/40DHLAs. Basically only racers run the 45s.
 

sdibbers

Well-Known Member
#14
I used to own Alfas and it's pretty odd that Rover was using 45DCOEs on this engine. You can make 150hp+ on an Alfa motor on 40DCOE/40DHLAs. Basically only racers run the 45s.
Well, they certainly liked big carbs on the TCs. The HS8s are 2” (50.8mm) jobs.
 
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