Beat the Dead Horse again 4.0 to a 4.6

Y

Yellow Defender

New member
Jan 19, 2024
4
4
Texas
Greetings and a 30+ year Rover owner of many Defender, Disco 1.
To take a 4.0 to 4.6 I have a few questions can’t seem to find the exact answer on the forms.

It’s the same block and same bore (cast liners) block number HRC 2411
The 4.6 uses a different crank rod and pistons and GEMS ECU selected for the 4.6.

I have several pull out junkyard P38 engines and ECU. Can you tell by the ECU part number if it’s a 4.6L or not?
Attached photos are the rod (piston) and cam that not sure if a 4.6L
IMG_0834.jpeg

I’ve heard that if you have the wrong ECU (4.0L) , it will run very rich damage the freshly built 4.6L Engine.

Also, after research Bosch engines seem the have much thinner wall from casting just being long production over the years seems Bosh 99-04 engines had much more liner, slip and head gaskets and the older P38.
If you were to top hat liner on a seasoned block would you use an older 1995 4.0 or a 04 Bosch engine block for a rebuild?

Regards
Alan Dobbs
 

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lunchbox

lunchbox

Well-known member
Apr 20, 2004
2,139
166
50
St Louis, MO
I ran my 4.6 with a 4.0 tune for a while. You can tell the ECU that it’s a 4.6. It for sure ran better after I made the change.
 
S

special ed

Well-known member
Apr 11, 2012
190
116
Elsinore
The difference will be compensated at the maf and O2 sensors. The computer just does its job and if it couldnt handle the change then you would have a check engine light. BTW ive done a 100+ of these builds with bigger cams and never neding anything to get it to run correctly. the computer just re adjusts the mixture to accomodate the 4.6. As for difference in the piston you can look at the top and the 4.6 has a deeper dish to retain the same compression as the 4.0. thats the easiest way to tell the diference. the piston on a 4.0 can be swapped onto a 4.6 rod to raise compression. And a final note on this thread is DONT use crower for a cam or lifters. Go with kent or piper.
 
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