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Discussion Starter #1 (Edited)
Ok I have searched alot of threads with no definitive results about the 4.0 conversion. Mostly 3.9's. I have a 97 that I wanting to convert to 4.6. I already have the crank, pistons and rods. Can I just change out those and be fine with the 4.0 ECU. Read it might run lean using the 4.0 ECU. or does something else need to be done? Also should use the stock 4.6 cam or go aftermarket? Also will this work in my truck Land Rover ERR7109 ECU Engine Control Unit 1998 HSE 4.6 ?
 

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I had the 4.0-4.6 conversion done on my D90 and the 4.6 will run fine with the 4.0 ECU. The ECU will learn to compensate, to an extent, for the longer stroke. I looked into installing a 4.6 ECU from an HSE in my D90 as well but could never get an answer as to whether or not it would work... maybe you'll have better luck. You can use the stock 4.6 cam or go to some aftermarket performance cam but that just depends I think on how much power you want. I stuck with 4.6 cam just cause I like to keep most things stock and I figured just having the 4.6 in a D90 even with the stock cam would be enough.

Just wondering, you said you had the crank, pistons and rods, so are you putting those in a 4.6 block? Or will they swap into a 4.0 and that's just another way of doing a 4.6 conversion? I know the 4.6 is the same as a 4.0 but with a longer stroke so are those blocks identical, one just has 4.0 parts and the other has 4.6? See I had a 4.6 short block with all the rods/pistons/cam, etc. already installed put in my D90 and reused my 4.0 heads.
 

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cant the dealership or a shop with the rovacom/autologic tell it that its a 4.6.
 

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Discussion Starter #4
I had the 4.0-4.6 conversion done on my D90 and the 4.6 will run fine with the 4.0 ECU. The ECU will learn to compensate, to an extent, for the longer stroke. I looked into installing a 4.6 ECU from an HSE in my D90 as well but could never get an answer as to whether or not it would work... maybe you'll have better luck. You can use the stock 4.6 cam or go to some aftermarket performance cam but that just depends I think on how much power you want. I stuck with 4.6 cam just cause I like to keep most things stock and I figured just having the 4.6 in a D90 even with the stock cam would be enough.

Just wondering, you said you had the crank, pistons and rods, so are you putting those in a 4.6 block? Or will they swap into a 4.0 and that's just another way of doing a 4.6 conversion? I know the 4.6 is the same as a 4.0 but with a longer stroke so are those blocks identical, one just has 4.0 parts and the other has 4.6? See I had a 4.6 short block with all the rods/pistons/cam, etc. already installed put in my D90 and reused my 4.0 heads.
I am using a 4.0 block and heads and etc. I use to rebuild 60-70 model ford motors and we use to buy timing gears that were advanced for better performance do people do that for the Rovers? Have not read anything saying so.
 

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the block and heads are identical, the 4.0 shares the same bore with the 3.9, 4.0, 4.2 and 4.6... a 4.2 is a stroked 3.9 and a 4.0 and 4.6 is a cross bolted main cap block... the 4.6 is a stroked 4.0..
d&d fabrications (aluminumv8.com) specializes in these engines, you can find a plethora of info and parts to build any rover engine to any configuration up to a 5.0 stroke ( I think they offer a rover race engine capable of 1000 plus hp).
in theory, you can take a gems 4.6 and drop it into a 4.0 frame and trans with out issues, reality of it all is that the 4.6 loves to eat hp22 auto boxes (it can be a long thread better left for a phone conversation)..
the 4.6 comes mated to a hp24 electronic controlled box....you can take a 99 to 2004 bosh engine, swap out the front cover, knock sensors and the crank and cam sensors, the intake of course and a few rotating assemblies and it drops into a gems chasis...I have knowledge of one bosh engined car retrofitted to to use a gems based shortblock while keeping the bosh management.
basically all gas rover engines (2004 and prior) will share the same basic bolt pattern of the bell housing.
the changes are bassically on the fuel mangement system (carb to fuel injection) and eventually electrical (from distribuitor to non distribuitor)... along the way it encountered a different engine management system due to emmissions. in the states, 1990 model adopted the 3.9 over the 3.5 them in 93 it introduced the 4.2. in 96 they introduced the 4.0 and the 4.6 until 2004.. then of course we all know the rr had bmw power plant the lr3 had the jag unit until 06 when all became jag powered units.
hope it helps a little and it is not confusing.
 

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Discussion Starter #7
To many Clams for the power stroke.
 

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The 4.0 ecu will work, but it's not correct. And using Rovacom or Autolodgic to change the 4.6 ROW setting does not work, either, and you'll get a transmission fault (1777). The truck will run rich up to op temp, and lean at throttle. The 4.6 setting also does not look for O2 sensors. A UK 4.6 ecu will eliminate only the rear O2 sensors.

Stock ign timing on a 4.0 advances to 50 degrees at 2000 rpm's.

Using a 4.0 GEMs ecu on a 4.6 you'll max out at 46 degrees @2000 rpm's. At 3800 rpm's you're retarding to 43.6 degrees.

Injector pulse rates are a concern, too. In other words, at full throttle you're starving the engine of fuel. An injector that flows a little more fuel would help, or maybe add a 9th injector on a relay. Both would be experimental unless you can find someone who has done this already.

By pulling the knock sensors you can retard timing 6.8 degrees at idle. Take that FWIW.

I'm not sure if Mark at D&D has a timing cog designed to work in an application such as this, but it may be worth a call.

If you want a higher HP 4.6 motor done right, forget about GEMs and go with a dizzy and toss on a Megasquirt. Or else plan to drop some coin on an ecu mapped to fit your engine.
 
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