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Iam contemplating boringout the boat anchor from 2 to 2.1ltrs. Anybody know the increase in power/ torque i should expect. I'm running 40's with 32mm chokes at present wich is great for road, but I could do with more top end power on track days.I don't want the expense of going to 45's but have been told that reasnable performance is still possible with larger chokes in the 40's.

Any advice would be welcome.


Korky :t-up:

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ian crocker

You can't beat the laws of physics.  If you change nothing except the capacity then you might get 2100/2000 or 5% more torque and maybe 2-3% more power.  Will you be able to feel that ?



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And thats assuming you will be able to suck the extra 5% of capacity though the existing holes ( valves etc.).....

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Peak torque isn't made at peak airflow so there wont be a problem with sucking the extra air as far as the torque is concerned.

32mm chokes would seem a bit small for a 2 litre making any serious horsepower, you can fit 36mm chokes to 40s but the venturi affect is not so good as with 36mm chokes in  a 45 barrel which can affect the signal through the aux-vent.

Generally speaking a pair of 40s is on the edge at around 150BHP, if you anticipate anythinmg higher then an increase to 45s would be worthwhile.

As Ian says the extra capacity you gain will be difficult to feel in delivered performance, you may do better to spend your money on improving the volumetric efficiency of the engine you already have.


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I have a 2.1 Pinto and had it bored out at the same time that I had the head seriously sorted out.  The tuner told me that the larger bore/capacity was worth 5% the other 50% coming from the head/cam/valves/carbs.  So on its own I would say a 2.1 litre bore-out (not cheap) is not worth the expense.

One thing that has always worried me slightly is the closeness of the cylinders after the boring - there ain't much metal for the gasket to sit on and the lack of positive location of the head on the block face causes me more worries.  Having said that, have removed and replaced the head twice and never experienced problems.

My 2.1 gives me 165BHP on an FR33 cam and DCOE 45's with 36mm chokes - all on lead-free petrol.  The strong point is the torque - loads of grunt from 3000RPM onwards.

Food for thought - the guy that did the boring warned me that some Pinto blocks do not have the bores centrally located in the block material and there is a risk of breaking through the cylinder walls when you go to 93mm or beyond.


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Having gone thru this excercise I would say that if you intend to go to 93mm pistons then you wil almost certainly need a 205 block to be on the safe side.

I understand that the wealls were slightly thicker so reducing the risk of breakthrough.

Having said that I went overboard and went the whole hog to create a bottom end that is now virually bullet proof.


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