Thread: Fitting 3.9 in place of 3.5 Discovery

Originally Posted by steve_35

That s why im asking questions i dont want to go and rip stuff out if i am going t have problems
ill just take it the mechanic and get them to do it if its a big hassle

It should be coming complete with ecu and airflow meter all the other goodies as i did explain to the guy what is was for and he knows land rovers so i think it should be all there ready to go in without to much fuss

I got it from AJG spares in QLD

i have worked on old Holden for years but this isn't a Holden that's for sure

G`day , i don`t think it`s been made clear to you .

If you use the serpy belt you`ll need Air con compressor and the Power steering pump and the Alternator and the Water pump and the Crank pulley and the Belt tensioner all to suit the Serpintine Belt ,of coarse the right lenght belt as well .

If you use the V belts , you`ll need to swap all your bits mentioned above AC ,PS , ALT , WP , tensioners etc with their brackets .

Which means changing the timing cover and at the same time working out which distributor you`ll use and its drive , oil pump .

The water pumps and fan viscos units are not interchangeable as in the 3.9 pump won`t physically fit on the 3.5 timing cover and visa versa .The 3.9 waterpump viscous mount is right hand thread and the 3.5 waterpump viscous mount is left hand thread . The Alt on the 3.9 is mounted in the middle and above unlike the 3.5 ...ETC.

Unless you get all the 3.9 bits for the front of the engine , i`d suggest that fitting all the V belt bits will be easier and cheaper because you already have it all .

The EFI stuff is pretty much the same as mentioned it`s really only the ECU its self that is different and will plug in the same as the 3.5 ECU

We have a 4.0ltr with V belts , it required the spacer Philip mentioned the 3.9 doesn`t as he also mentioned .

Cheers

Originally Posted by steve_35

Thanks PLR

That makes it perfectly clear i was starting think i had made a mistake buying a 3.9

If i have the whole 3.9 fan to flywheel it just bolts in but ill need to do something to something dont know what but something will need tweaking

its easier to strip the 3.9 and use everything from the front of my 3.5 engine just swap it over it will definitely bolt straight in no tweaking

Essentially the long motor is exactly the same its the bolt on stuff that's different

does that sound right

Yep ,
the problem with the serpentine is it has to have all the pulleys to suit ( which you have for the V belts ) . If it comes with the AC compressor and the Alternator and the Power Steering Pump then it should be possible to fit the pipes and regas the AC and it should be possible to fit the pipes to the PS pump , the Alt may need the wiring extended a little and possible different ends on the wires .

So then the serpy may be the way to go ?

I don`t think it would be feasable to purchase serpy pulleys seperately unless you know of some cheap ones and then there`s a need to work out which will fit with what , i know the two PS pumps bodys are totally different , the pulleys are held on by three bolts on each one but don`t know if they interchange or will clear if they do .

You can be sure if you go the 3.5 frnt on the 3.9 that it will work the same as it does at present .

Yep basically the same engine in this instance from the outside , different on the inside but they can share some internals .

When the 3.9 appears you`ll be able to look at it and work it out .

If you have any major dramas we have as said a 4.0 with V belts and a 3.9 serpy in our RRs and other engine stuff in the shed so should be able look or measure if needed .

Something you should know is that no matter which pulley sets you use it`s very important that everything lines up and runs true , so there will be minimum noise and wear .

Cheers