engine swap questions

ArmyRover

Well-known member
Dec 4, 2007
3,230
0
Augusta, GA
Well I returned from a 3000 plus mile trip in the RRC and have found the rear main to be leaking. So from my searches I find that I will have to pull the motor to repair this so first I'm going to check compression etc before I yank it. If it looks like she is in need of a rebuild that begs the question of do I:

a. rebuild the current 3.9
b replace with a 4.0
c. replace with a 4.6
d. go small block chevy
e. go diesel (any thoughts on which diesel and any write ups on the swap would be helpful as well)

Good write ups on any of the above would be great as well. So I can gauge the degree of difficulty of the swap.

I guess I'm looking for thoughts and recommendations from you guys so lets hear what you all think.
 

Pugsly

Banned
Apr 20, 2004
382
0
www.roverautomotive.com
if you decide your block is okay, consider rebuilding it as a 4.6 - the 4.6 is a stroker, so to go from 3.9 to 4.6 just requires a different crank and connecting rods.

There is no displacement difference between the 3.9 and the 4.0 - changing the numbers was a marketing thing Land Rover did when they went to the coilpack ignition. It will take quite a lot of work and you really won't gain much.

While fun to think about, the diesel swap or chevy swap will be far more expensive and time consuming than you could ever imagine. Its not the actual engine that will get you, it is everything else that you have to change / fabricate in the process. Wiring harness, ECU, exhaust, motor mounts, radiator hoses, power steering, transmission adapter, etc, etc.
 

57loboy

Well-known member
Oct 17, 2007
912
2
Fairfield County, CT
I've got a 4.2 with good compression I am looking to sell that would be a direct swap for what you have...No leaky mains either! Check out the parts for sale section - I am in CT.
 

Drillbit

Well-known member
Oct 12, 2005
5,943
0
Glasgow Ky
Yeah, a 4.2 is probably your best opition, espically for what loboy has it listed at. Its a drop in install and you get some extra power.
 

RRCNicky

Well-known member
Dec 6, 2006
533
0
Doesn't everybody's rear main seal leak? Mine's leaked for 3 years, leaves spots everytime I park - compression is stellar. I just keep an eye on the oil...
 

ArmyRover

Well-known member
Dec 4, 2007
3,230
0
Augusta, GA
I'm now leaving a coating of oil on the back of the truck up the tailgate and glass. I think it has passed beyond the normal range of Land Rover automatic undercoating system performance

I did forget the 4.2 in that list and is also one I'm considering as well. I just wasn't sure if if was enough of an improvement to be a better choice than a fresh 3.9.
 

Pugsly

Banned
Apr 20, 2004
382
0
www.roverautomotive.com
Definitely. a good used 4.2 will be a strong motor and the most economical option. If you keep the 3.9 and then rebuild it and sell it you could further reduce your out of pocket expense...

Oh, if possible swap the motor/transmission as a unit. The 4.2 has a beefier transmission to handle the stronger motor...
 

Ron

Well-known member
Jun 15, 2004
1,820
0
Main Line
It is just the cross seals. They can be replaced in situ.

Buy the new rubber ones, not the old style cork/rubber ones.
 

lforgue8

Well-known member
Jul 23, 2006
1,207
0
MA
ArmyRover said:
really from what I read I thought it was a pull the engine job.
Cross seals and rear main can be done in car....trans needs to come out and oil pan dropped. the last main bearing cap is then taken off to replace cross seals. reinstalled cap but dont torque yet install new rear main and then torque cap and reinstall everything...........but.........if you plan on "refreshing" the motor with new bearings and such then removing engine would be the way to go!

Good luck!