Swapping Motors 4litre OUT 3.9litre IN

[beancounter1]

I was just wondering what issues or problems might arise if I remove a 4litre motor (multipoint injection) and replace it with a 3.9 litre motor (from an EB series 1, centrepoint injection).

To minimise problems, I think I might just swap the block, head, top end, starter, distributor, etc. I will retain the old inlet, multipoint, exhaust manifold, airbox.

Are the distributors the same on both motors ?

The 3.9litre motor was attached to an auto gearbox, and I will be hooking it up to a manual gearbox. Will this cause any special problems ? Will I need a new computer box or wiring ?

I know the 3.9litre motor has recently been reconditioned, no leaks and lots of life left.

Any tips for a novice like me would be greatly appreciated. I have an endless chain, but no hoist. Is it easier to remove with or without the gearbox ?

[BOOSTDEF]

I found it easier to remove with the gearbox still in tact, but i couldnt get it back in like that lol dont ask me why...

The 5 speed gearbox will slot straight on the 3.9 im pretty sure. But i think the 3.9 may have a different flywheel??? im not certain..

Also, i know cpi and mpfi have different fuel pumps, so maybe check if the distributers are the same.

Other than that if you use the manifolds that are already on youll be fine.

[pantic]

you need a manual wiring loon replaces the old auto loon and you would need a manual computer. helps with controlling the idle. some cars stuff up from manual conversions some dont. you will need a clutch flywheel and a clutch :P~ where i work im not to sure if there is a different dizzy but we normally mark em as MP or CP so im guessing yes there different.. i would keep everything off your motor back on besides the auto loon replace that with a manual one... there cheap to buy hard to find. :P

[Damo]

just use the whole motor with no accesories or manifold and use all your existing stuff, everything will bolt up fine, they are the same motor just with slightly different internals. I have done the swap 4.0>3.9 and everything went fine except for the fact that the 3.9 I put in had no compression on 4 cylinders, but that's another story.

[NC_GHIA]

Why Why Why go down and back in motors whats so good about the 3.9 over the 4.0...


Hence the fact I have a 3.9 CPI...

[Perana]

CFi distributer is different to the MPi one so make sure you use the MPi one.

[Rmyers]

Originally Posted by Perana XR8

CFi distributer is different to the MPi one so make sure you use the MPi one.

Yes it is different but many have done the mpfi conversion without changing the dizzy and haven't had any problems.

[LUXO_8]

Originally Posted by 6cylEA

Why Why Why go down and back in motors whats so good about the 3.9 over the 4.0...


Hence the fact I have a 3.9 CPI...

because he said the 4.0 is stuffed and the 3.9 he has has been reconditioned..........

if it were me i'd do the same......

[beancounter1]

Thanks for those replies.

Do I really need to change the wiring loom and computers. I am not swapping gearboxes - just motors. The 3.9 motor is presently attached to an auto gearbox and the 4litre motor is presently attached to a manual gearbox. I am only changing the block, head, sump, etc.

The old 4litre motor is stuffed...it has done 400,000+ km, head gasket stuffed, head has been shaved 3 times, oil leaks, etc, etc.

Do these motors both have the same flywheels ? - no alignment problems or adapters required for different gearboxes.

It sounds like I need to keep the 4litre fuel pump.

Swapping the distributors sounds simple enough - pull one out.... plug one in - or does the timing need to be reset ?

[Perana]

If your keeping the injection thats on the car at the moment you wont.. just swap the block/head/sump etc.. But you'll need to use the flywheel on the 4.0

[naughtyfalcon]

if your swapping the motors and keeping the same box theres no problems,,you'll just need the flywheel off a 3.9 as i think the 4 litre fly wheel has six bolts and the 3.9 has 3..i think.

[Damo]

^^^ NO!

The flywheels are the same apart form the mounting holes/dowels, it's the clutch that is different EA/EB1 = 3 bolt EB2 onwards = 6 bolt, they both bolt to the crank the same. Just use all the stuff off your 4 litre and it WILL all bolt on fine.

[naughtyfalcon]

ah i knew there was a difference somewhere,,thanks for that.