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Both the O-Series engines are identical in the Princess and Ambassador, so it seemed as though it would be a fairly straightforward task taking the twin manifold and carbs, SU HIF44ís, from the Ambassador and bolting them into place on the Princess.


After fitting new gaskets, the inlet manifold fitted straight on to the Princess cylinder head, though some slight grinding of the manifold was required as the outer edge of one of the end boltholes fouled the water hose on the cylinder head (there was a slightly different arrangement on the Ambassador). Once in place the carbs were fitted along with the ASU, the Automatic Starting Unit, which is basically an automatic choke.


I was told that it had only recently been fitted to the carbs and was in good working order, it seemed ok on the Ambassador but it wasnít running very well as it hadnít been used for 18 months. When I started the Princess up, it all seemed fine, but as the engine got warmer it started to hunt and misfire. Fiddling around with the mixture adjustment seemed to make things worse so, using the Haynes manual, I tested the ASU, and as far as I could tell, it was knackered!




I phoned an ex-BL mechanic who was recommended to me by another Princess owner, and he said that the ASU is more trouble than itís worth and the best thing to do was bin it and use a carb with a manual choke arrangement. A conversion kit for the ASU is available but I was told that is also quite unreliable. So I thought Iíd use the single carb that was originally fitted to the Princess and make that one of a pair, as itís the same type as the twin carbs. Not easy. I found that the throttle opening on the single carb opens upwards, while the twin ones open downwards. Shit!


So, plan Z was called into action. I have a pair of carbs from a Princess 2200 - SU HIF6ís, and according to the manual, the specifications are near identical to the HIF44ís, so on they went and it was pretty straightforward. The carbs are further apart on the O-Series so I swapped the links around, the choke didnít need to be connected as only one carb needs to work for the choke (so I was told). I used the Ambassador filter housing, which I had to modify for this fitting as the throttle and choke cables pass right through the filter housing.


The Princess 2000HL is some 150kg lighter than a fully loaded Ambassador VP, so it was going to be interesting. The carbs were balanced and tuned by an ex-BL mechanic, and although he had difficulty getting a smooth idle, it is acceptable. The mid-range performance is markedly improved, though I still have yet to do some proper performance testing. Nevertheless, the overall result is pleasing.










I fitted some alloy wheel brake dust protectors, which I bought on ebay to keep the front wheels free of brake dust, as it was a real pain having to constantly keep cleaning dust off of the alloys after each journey. Whilst I was at it, I replaced the brake pads.













I have also updated the ĎSTí logo on the rear of the car, which I cut out of some special chrome vinyl and stuck it onto a piece of matt black vinyl, then stuck that over the original HL badge. Sporty!




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This page updated 11th August 2005.









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