Swapping 4.2 for my tired 3.9

[kjj0506]

Any one have any insight before I dive in?

My tired old 180k + 3.9 has a lifter or rocker tap and the oil and coolant smell gassy. I was going to yank the heads and throw a upgrade cam , t chain and ne rocker shafts ( along with all the other wear stuff on the top end ) in but found a very nice 117 mile 4.2 for sale for 700.00.

I am wondering if there will be a significant seat-o-the-pants difference. Is there a big change in power and torque? Mileage?

Is there any thing I should look for or be prepared for during the swap or is it just a straight forward exchange?

Thanks in advance

[Bobtail]

Its a straight swap as they say :-k


as with all easy things it will probably be a son of a bitch


Good luck [-o<

you will need it...........after all its a land rover ](*,)

[Rossko]

When I've driven 4.2 it seems to me the extra torque from the long-throw crank is noticeable over a 3.9, but out and out power not really noticeable.  Dunno about consumption, not a lot of difference?

cheers

[kjj0506]

Is there an actual difference ? I am certain there will be one hen comparing mine to a newer good mill but curious what the specs are .

Thanks if you have them

[Range Rover Blues]

3.9 is what, 180 BHP?
4.2 listed as 200BHp all bar the shouting.  It was supposed to take the RRC LSE to 60 in 10 seconds but I don't think it wuite made it in reality.  On a stock 3.9 100"WB it might pove a quick thing.

The CR was lowered from 9.35 to about 8.6 IIRC, both engines use the same dizzy but the 4.2 (4275cc) was set at 10 BTDC as opposed to 4 BTDC, as a measure of how much lower the compression was.

So one route might be to raise the cr back to around 9.2, this is possible with a light skim of around 0.5mm.

The extra torque will be nice.

The best thing is that if the engine is looked after then at 117k is can be a good one, look inside for signs of neglect.

Also they can often expire well before reaching this age and some say it's down tot he ECU, it runs too lean and at low revs causing the porous block syndrome.  Worth having it re-mapped anyway but this is not cheap, around £300 from RPI as an example.

You run the same if not greater risk if you try to run the 4.2 on your 3.9 EFi but htis can be remapped for the same money, if you get the 4.2 ECU then sell it on (they still fetch a premium price) and re-map your 3.9 one