3.9 to 4.6 swap?

[SGFMORover]

so as we've addressed my 190k mile 3.9 has some issues, excess pressure, ticking heads (louder each week), and well its got almost 200k miles for god's sake.

so the debate is this; tear down and rebuild the whole bloody thing; or now i've got a fella i do work for offering me a 4.6 low mile disco engine for next to nothin (maybe a grand). I know swaps have been beat to death on the forum but I can't seem to find straight answers to what is involved.

so does anyone know what all i'd have to swap with the engine to make it work? tranny? ECU? wiring? i'm assuming power steering, a/c, alternator would all have to go? anyone know if the mounts match up?

help? i'm moving from colorado to NJ this fall so if I'm gonna swap i may need to get on it. otherwise I may try to find a shop near NJ that will do the rebuild for me. not much in southern colorado that I trust.

[Joey4420]

ECU will need upgraded... most of the accessory mounts will not work off of the old engine, and you will have to use the older fuel system unless doing a complete upgrade (PITA) also the 3.9 has a distributor and the 4.6 does not... so it will be fun, but not impossible.

[Beemer Nut]

Joey, that you from long ago I believe on another Rover forum?
Still have my 95 5 speed 4.6 powered D1, not a stocker just a fun street sleeper that hangs corners not for dirt.

Back to the OP, yes a 4.6 will drop right in using all the old 3.9 engines parts your just replacing the short block plus install a new timing cover with oil pump as the old one will be shot by now. Do rebuild th heads this time properly not the Rover POS sticking valve problems. The old ECU chip must be changed to fuel the motor properly, I run a RPI Tornado chip. I leave it in and pass California smog at less that 7% at idle and 9% at the 2,500 rpm sniff test. It fuels properly and pulls hard to 5,900 as the chip fuels for max power but leans down under cruise. I can do rolling stops just legal in second, dump clutch below idle rpm's and pull away no problem. With the old 3.9 it fall on its face. This with a Piper 260 cam with a roller timing chain set. Port matched intake to heads, heads to iron exhaust manifolds, factory port matching is total garbage. Your leaving a lot of restricted power with this crappy with carSound's MagnaFlow high flow cats with Borla cat back exhaust.
.......=o&o>............

[Beemer Nut]

so as we've addressed my 190k mile 3.9 has some issues, excess pressure, ticking heads (louder each week), and well its got almost 200k miles for god's sake.

Wow 200K! This may be the high end on anything British Rovers included.

I'm at 283K and bored with the engine thinking 520 cu/in the next build, the last motor went 473K and never opened up. Something to be said about old American Iron especially the Ford FE motors.

[Joey4420]

Yes beemer nut... I am the same joey off of landroverworld, still there everyday.

[Beemer Nut]

Good to hear from ya Joey.

I'm about to replace the valve cover gaskets, starting to leak, this is the first time at 138K miles, PO with 62K, the plenum has ever been staken off even with the 4.6 dealer swap. Original from new back in 95. It ran good but not as well as it should even with that 4.6 swap. I found one trumpet out of its pocket rattling around against the plenum top. It always had a little detonation on one cylinder above 4,500 rpm's. Lucky me as I located a trumpet base for $20 last month at Pick N Pull. Also got a complete ABS system, sensors, ABS computer as well every relay. Got the ABS to work with no dash light.
Remember my strange ABS fault code numbers, the ABS computer took a dump. All is well until last month now the SRS started to blink and now stays on. Living on a 1 1/2 x 4 1/2mile island this D1 never leaves the island as the wife with repacement knees does not want to be ever stranded again. Well the SRS went on so she parked where it came on and took a cab home. She is totally done as someone told her a airbag could blow up into her face hence she will never sit in it or any Rover ever again plus will buy her own car. So SRS to look into besides the VC gaskets. Adam I was told can recurve the Tornado chip from RPI as it has always gone lean at the transfer from closed loop to open, a lean stumble as I changed the resistor at the ECU harness and it went away so a remap of the chips needed. More testing with a wide range O2 sensor with recorder to fully find out what's needed.
Question; did the D1 like my 95 have a left motor mount heat shield like the right side? Mine's without one and the mounts now toast. This missing if so from the engine swap by the dealer as well the exhaust manifold bolt lock taps. The typical door lock spring failures, a replacement kit from England waiting to be installed. Carl......=o&o>.........

[JimC]

Definitely run some searches over at d-90.com about the 4.6 swap, lots of good info. I just did one (with a motor someone else had built up) and almost the only thing different is the block itself. 4.6 Discos run the serpentine system and the front is completely different.