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Engine 253 VIN 3052

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Old 07-05-22, 07:59 AM
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Default Engine 253 VIN 3052

Hey Everyone,

my name is Christian and I am the happy new owner of #3052.

First it ran great, but after some miles the carbs started to overflow and I had to toe her home. There was some dirt in the carbs and the fuel filter, so I took them apart and cleaned everything.

I noticed that the pumps were not connected to the throttle linkage. Although on many pictures of other cars they are, some people say they weren't when the car was new.

I have Solex 32 PBI-6 on top of my engine. Can anyone help with a jetting chart or/and a workshop manual for the carbs. I have only the engine manual and the carbs are not looked at in detail.

Thanks a lot
Christian
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Old 07-05-22, 11:36 AM
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Christalfa,

The carburettors fitted to your engine were originally fitted to an AC Ace or Aceca Bristol with 100D or 100D2 engine. The jettings for these and original Arnolt Solex (32BI) are similar.


B32PBI-6 Venturi /Choke 28mm,Main Jet 125, Air Correction 190,Pilot Jet 55, Pilot Air Bleed 1.0, Emulsion Tube 10, Needle Valve 1.5 ,Float Level 16mm , pump jet 95

32BI Venturi 28, Main Jet 135, Air Correction 240, Pilot Jet 50, Pilot Air Bleed 1.0, Emulsion Tube L24 (special), Needle valve 1.5 , Float Level 16mm
Pump Jet ( None fitted)

Your Arnolt 3052 in the early 70s was fitted for a while with a D or D2 engine
but was later replaced by the original BS1 Mk2/253. Have you checked the actual engine numbers stamped on the block close to the top starter motor bolt and on the head on two raised bosses on the distributor side.
Pls advise those engine numbers.

Over the years I have had two D2 engines fitted in a AC Ace and Bristol 400 .
For road use I could not get the engines to run correctly until I blocked the pump jets . The pumps on your Arnolt have been disconnected and I suggest you leave them like that .
From memory I increased the size of the main jets from 125 to either 130 or 135 and increased the air correction jets from 190 to about 210 .
I covered more than 60,000 miles in my 400 with that engine , which always ran strong and delivered 28 - 29 mpg touring at about 70 mph.

I also suggest you have the Arnolt dyno tuned or at least get the use of a mobile gas analyser to confirm if the engine is running rich or lean .
Over nearly 70 years most of these engines have been modified with different compression & valve timing and of course the fuel today is different to the 50's.

I hope this is of some help

Geoff
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Old 07-05-22, 12:22 PM
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Default Accelerator pumps on 2 litre engines

These are often disconnected, mine have been by the tuner guy, and I'm told that they don't improve performance and also that they will leak if you're not able to use alcohol free fuel.
And the carb floats do stick up and cause floods. Some people carry a little " carburettor hammer" - a sharp tap will dislodge the stuck one.
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Old 07-05-22, 08:29 PM
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Thanks for your fast help! That's correct, there was another engine fitted. At the moment I am running original 253. The carbs were full of dirt/deposits. I have fitted a modern paper filter between the pump and the carbs for the moment.

The car starts good when cold. When it warms up, it starts to choke when opening throttle. It starts really bad when warm. I will check the base setting and ignition.

When it runs solid cold and warm, I would adjust the jets by measuring AFR while driving?!
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