Thread: 4.6 into Disco...Just how easy is it?

Depends which way you want to go on the fueling...

If you stick with the original system, you'll have to re-map to take care of the extra requirements of the larger volume... (Assuming the injectors & ECU can cope).

Or...

Transplant the newer top end which will involve some electrical work to work out which bits of the old system you'll need.

My personal preference would be the second option... But then my skills are more biased to the electrical side of things.

Gearbox... I didn't think your gearbox had an ECU (but don't quote me on that). As for the physical fitment, IIRC the block should be identical.

M

You'll need to pressure check a used 4.6 very carefully to avoid the cracked liner problem. Especially one from a P38. Avoid the 4.0 blocks too, they are reportedly the ones with the least meat between the water jackets and the bores (read Des Hammill's chapter on the factory colour coding of blocks and posts about this issue on www.v8forum.co.uk :: Index).

The hotwire system will work ok with a 4.6, it was used on the 4.2 RR, but to get optimum fuelling for the bigger capacity you need to re-chip the ECU. And that means swapping in a Tornado chip - get it from Mark Adams in the UK (not RPI).

I was of the understanding that the injectors are the same on the 3.9 and the 4.6 (ERR 722), but may be wrong.

I have reseached putting one of these engines in a 1990 V8 County that my Father owns. He has since bought one and in now being rebuilt. The couple of little snags are is the 4.6 had the option of the starter motor on the LHS not the RHS all though I haven't seen one like this. Another is they had a different timing cover which puts the water pump and fan in the wrong position for a county. The older ones do fit though. The only real problem with the engines is cracks in the block. Although rover engine have liners the 4.6, 4.0 and 3.9s did have a problem of the aluminuim section cracking and then water tracking up between the bore and the liner then entering the cylinder. This problem is over come by putting in T sleeves which have a lip on the top like a T and this then seals on the head gasket. The cracks still happen but water doesn't then get into the engine. As far as I understand the injetors changed about 1991 and were the same onwards but am unsure about the injectors in the thor mainfold. I have my 4.4 Leyland v8 running on a 3.9 computer and runs ok but am going to get it rechiped next year along with LPG injection.
Tim