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Badger
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"Badger" <[email protected]> wrote in message news:...
>
> "Aubrey" <[email protected]> wrote in message
> news:[email protected]...
>>
>>
>>
>> My thinking is more conservative (although I run a Discovery that started
>> a
>> 4.0 and now claims to be 4.6 and a 250 kW Defender) The 3.5 block is
>> weakened by the boring and also, bigger more does more for power than
>> torque.
>
> Hmmm... general rule of thumb is that more cubes = more torque, you need
> to make considerable breathing improvements to get the power that the
> capacity increase is theoretically capable of producing. That is why the
> 4.6 produces good torque but low power for its size, compared to the 3.5,
> it is restricted by breathing.
>
>>
>> I would rebuilt with 10.6 compressions Rover SD1 pistons, 3.9 cam from
>> LR,
>> gasflow heads, profile valves, free flow exhaust and either turn up fuel
>> pressure or rechip. This setup will make more ponies than a 3.9 and will
>> be
>> reliable.
>
> Turning up fuel pressure without recalibrating the rest of the system will
> not give more power. See thread elsewhere about cam timings, do not be
> fooled about 3.9 cams, it is a 3.5 SD1 cam advanced by 2 degrees!! You
> may end up with slightly more power, but you will have a lot less torque
> at lower rpm's - where a 4x4 needs it most!
> BTW, what pistons would you use to achieve 10.6cr?? Highest cr SD1 piston
> was 9.75, P6 was available with 10.5 but a weaker piston that doesn't lend
> itself to higher power outputs, it also has thicker rings that cannot
> accept higher revs reliably, higher revs being what your suggested mods
> would give more power at.
> Badger.
>
>
>
