who has gone from 4.0 to 4.6

trailhogg

trailhogg

Well-known member
Feb 26, 2005
377
0
45
Hermitage Pennsylvania
I am about to do this and am curious about others who have done it and what they think.

Was it a worthy upgrade?
what differences do you notice?
Is the 4.6 more long term dependable?
Gas mileage better or worse?
Any lurking problems with the swap?

thanks
chris
 
OFFROVER

OFFROVER

Well-known member
Dec 7, 2005
267
0
46
Knoxville,TN
I did it on my 96 DI, swapped 4.0 GEMS for the 4.6 Bosch w/ SAI. Had to change alot of things you would not have to deal with since you all ready have a bosch. I thank it was worth the money and I've only put 5k on it since the swap but not a single engine problem yet. But I also went from 170k 4.0 to a 0 miles 4.6.

~Corey
 
Slappy

Slappy

Well-known member
Jun 17, 2007
1,441
0
Santa Clara, CA
My 99 D2 has a 4.6 in it. There is a difference in power. I'm running 32" tires with the stock 3.54 gears and I never have to drop it in 3rd gear going up hills like I did with the 4.0, and I live in a very hilly/mountainous area. Going from a bosch 4.0 to a bosch 4.6 is a very straight forward swap. I highly recommend doing this upgrade, if you need a new engine. With that being said, I wouldn't have gone through the trouble of upgrading to the 4.6 if I didn't need a new engine already. I was planning I doing diffs/gears/axles until I had to spend my cash on a new engine. Now that'll have to wait a bit.....
In your case, since you need a new engine, you might as well upgrade.
Good luck.

edit- mileage is the same.
 
Bahnstorm

Bahnstorm

Well-known member
May 22, 2004
141
3
Ithaca, NY
bahnstorm.com
Was it a worthy upgrade?
~Yes. Did all the labor myself and got a nice deal on the 4.6 so cost was reasonable.

what differences do you notice?
~Uphill hauls are much easier.

Is the 4.6 more long term dependable?
~To be determined. Only a year and half in. I don't know why it would be much different than any other new engine.

Gas mileage better or worse?
~About the same a bit better overall according to my log book. Works less on the hills around where I live, but I might push it harder to enjoy the exhaust note.

Any lurking problems with the swap?
~I also went GEMS to 0 mile Bosch plus the headers and like Corey said there were quite a few little gotchas that a Bosch to Bosch swap won't have, but really nothing too tricky if you've swapped engines before.
 
trailhogg

trailhogg

Well-known member
Feb 26, 2005
377
0
45
Hermitage Pennsylvania
ok i am gonna hijack my own thread...

i am suddenly fearing that even though i am getting the 4.6 ecu with the engine that it wont work, or sync up, in my disco.

Those that have swapped, how did you handle the ecu issue?

did you reprogram your disco ecu or swap it out completely?

you gems guys most likely had to swap out.

thanks
 
lunchbox

lunchbox

Well-known member
Apr 20, 2004
2,141
166
50
St Louis, MO
I did a gems to gems 4.6 swap. I had to hook it up to Autologic and tell the truck a 4.6 was under the hood. Made a clear difference.
 
craig

craig

Well-known member
Oct 1, 2004
1,747
0
Edmonds, WA
overlandnavigator.com
Don't swap ECUs. Use the top end from the 4.0 and just put a 4.6 shortblock in.

I did it several years ago. it works, power is great, mileage is a little better... no downside and very straightforward
 
R

RamRod

Well-known member
Jun 20, 2008
103
0
Tampa, Florida
One quick question... Brand New to the rover thing just bought a 97 disco like 3 weeks ago how will I know if it has a Bosch or a GEMS and what does it stand for i.e. whats the diffrence... coming from a wrangler so its a little different from the old 2.5 or 4.0 ... also I just ordered a 5.2 Interceptor motor has anyone done this swap before... I am a service manager for Nissan before I was a tech so I have the lifts and air all labor will be done by me is there anything elese I should know before I start pulling harnesses.... Thanks!!
 
flyfisher11

flyfisher11

Well-known member
May 25, 2005
8,676
2
61
Wolf Laurel NC
RamRod said:
One quick question... Brand New to the rover thing just bought a 97 disco like 3 weeks ago how will I know if it has a Bosch or a GEMS and what does it stand for i.e. whats the diffrence... coming from a wrangler so its a little different from the old 2.5 or 4.0 ... also I just ordered a 5.2 Interceptor motor has anyone done this swap before... I am a service manager for Nissan before I was a tech so I have the lifts and air all labor will be done by me is there anything elese I should know before I start pulling harnesses.... Thanks!!
Click to expand...

Yours is GEMS. Look at the intake. All D1s were GEMS and all DIIs are Bosch unless for some reason a previous owner swapped it but highly doubtful. It is merely engine management in a nut shell. Where did you get an interceptor motor?

This is the only place I've seen doing the interceptor and they won't touch a disco, snobs!
http://www.eastcoastrover.com/RoverV8.html
 
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R

RamRod

Well-known member
Jun 20, 2008
103
0
Tampa, Florida
I purchased the Engine through RPi Engineering paid about $4600.00 U.S. w/ shipping and everthing.... It's the short block and I am going to do the R&R my self
 
agbuckle98

agbuckle98

Well-known member
Mar 10, 2006
1,831
1
lunchbox said:
I did a gems to gems 4.6 swap. I had to hook it up to Autologic and tell the truck a 4.6 was under the hood. Made a clear difference.
Click to expand...

Can a T-4 machine also tell the ECU it is now controlling a 4.6 instead of 4.0?
 
nursemcdonald

nursemcdonald

Active member
Oct 22, 2004
39
0
Yakima, WA
I did the 4.0 to 4.6 swap exactly 1 year ago. NO ECU change, NO reprogramming needed. Upon start up the engine idled up to about 6000 RPM and then backed down automatically in 5000 RPM increments untill she idled around 900 RPM.

Very satisfied with the swap. Easy install with just a few hangups I dont know I could have avoided, but then again not very bad either. I would suggest you invest in the workshop manual, long-long extensions, swivel extensions and wobble extensions...

good luck, you will be very happy. I will soon consider putting a bigger engine into my other 3.9 DI; but which engine to drop in im stilll undecided...
 
B

Boris

Guest
Just completed (6/25) a 2001 4.0 Bosch to a NEW, yes that's NEW 4.6 short and rebuilt 4.0 heads. No problems, no ECU reprogramming, mpg remained the same. The original 4.0 had an overheating problem resulting in new radiator, rebuilt heads, new coolant lines, new gaskets ..... then new short block.

Performance is noticeable, but not impressive. Remember that within the typical rpm range the gains are 10-15hp or so and equivalent torque. I'm doing some exhaust work this week so we'll see how that translates into gains. Looking for an additional 1mpg and a better exhaust note.

-Boris
 
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