The Official 4.6 Conversion Thread - Defender Source
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  #1  
Old January 24th, 2010, 10:53 AM
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The Official 4.6 Conversion Thread

OK, since test driving a NAS D110 4.6 I believe that the 4.6 is the most user friendly D110 engine for the daily driver ect. So I thought I would start a 4.6 NAS conversion thread to help others on their journey too. Don't get me wrong I love the diesel engines, and think they sound like they belong in a Defender. But my own concerns for daily driving and DOT BS down the road make me lean towards the 4.6.
As for off-road, the perceived disadvantage of the 4.6 over the diesel are water, and low end torque. So with the 4.6 one may want to stay out of the deep end, and buy and under-drive for the transfer case.

4.6 engine options: (Links provided below)
Short Block/Long Block from Atlantic British and use the 3.9 parts I already have
Complete Engine from RPI
Complete Engine from JE Engineering

Transmission/Transfer Box:
Can an R380 handle HP up to 300 and torque to 350?
RPI says it can
The 4.6 D110 I drove still had the original LT77S, and I was advised to start from stop in 2nd.
What about the transfer box? Can it handle the extra power too?

Computer/ ECU:
What is best, a 4.2 ECU, 3.9, 3.9 chipped, or 4.6?
RPI will provide the ECU.
The 4.6 D110 I drove was also running on a non-altered 3.9 ECU, and had plenty of power.


From what I can tell RPI offers a complete plug and play 4.6 (anything and everything needed), and transmission (R380), clutch/fly wheel, ect. They like JE Engeneering offer a Stage 1, 2, & 3 power upgrades.

Jim and Chris, please feel free to merge other 4.6 threads to this one.
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  #2  
Old January 24th, 2010, 01:32 PM
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Quote:
Originally Posted by Jon_Winningham
When it comes to shop manuals for my Defender, I always reach for the Necronomicon first.
The Mad Arab has lots of good techniques for Rover repair. I've lost several insanity points working on mine.

Now back to the 4.6 thread.
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  #3  
Old January 24th, 2010, 09:29 PM
Tyler Wirken
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Glad you started this.

I have been thinking about this for my project for a long time. So here is my question for the experts.

I have a 4.0 GEMS. So logic tells me that if I were to tear down my motor and have it bored out to 4.6 then I would just need to buy some 4.6 pistons and rings I would be good to go? Granted I never said it was good logic but school me a bit here.

Is the cam, crank etc.. all the same from 4.0 to 4.6?



Thanks
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  #4  
Old January 24th, 2010, 11:36 PM
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Tyler,

The bore is the same on the 3.9, 4.0, 4.2 and 4.6. The 3.9 and 4.2 share the smaller main bearing journals than the 4.0 and 4.6 whose main bearing are also cross bolted. The 4.0 and 4.6 blocks are the same. The difference is the crank/rod/piston/camshaft which are different.
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  #5  
Old January 25th, 2010, 06:02 AM
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Has anyone ran 4.0 pistons in a 4.6 conversion?
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  #6  
Old January 25th, 2010, 07:52 AM
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Computer/ ECU:
What is best, a 4.2 ECU, 3.9, 3.9 chipped, or 4.6?
RPI will provide the ECU.
The 4.6 D110 I drove was also running on a non-altered 3.9 ECU, and had plenty of power.

Megasquirt 3. No question. If you want plain old plug and play then the 14cux box is plenty fine. For the price of a custom chip you can have a Megasquirt 3.
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  #7  
Old January 25th, 2010, 07:54 AM
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I almost think it would be better/cheaper in the long run to buy a new long block from RPI. But for sure the 3.9 guys may want to consider the plug and play new RPI 4.6 (maybe even their stage 3) with the non-distributor cap set up.

I am leaning towards:
RPI's: 4.6 Turnkey "Serpentine" Engine
New R380
New AC from Rovers North RNAC40
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1993 NAS Defender 110 #375/500: Sold
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1993 NAS Defender 110 Beluga Black #215/500: sold
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  #8  
Old January 25th, 2010, 08:33 AM
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I have other ways to spend $10K+, which is what you will pay just to get the turnkey engine here with no installation. I don't know what you mean by better/cheaper--a 2.8l Powerstroke conversion would be better for that dough. There basically isn't a build up that I can think of doing that would run 10K before installation. But if you have that kind of money, then go for it.

As for using the 4.0 pistons, I looked into that and did some volume measurements--I will have to check my notes, but the compression started to border on 11:1 which was higher than I wanted to run--I wanted to stick to fuel that one could borrow on the trail and didn't want to carry around octane boost everywhere.
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  #9  
Old January 25th, 2010, 11:21 AM
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Jon - I think you should consider the option of building up a 4.0/4.6 block. If done right, it will be just as good as your other options, and considerably cheaper. As an example, I bought a used 4.6 crank, rods, and pistons (22K miles), with new rings and bears from UK (via RPI) for around $800 to convert my 4.0 to 4.6.

For Phil's question, see attached. 4.6 on the left
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  #10  
Old January 25th, 2010, 12:03 PM
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Quote:
Originally Posted by Davis View Post
I have other ways to spend $10K+, which is what you will pay just to get the turnkey engine here with no installation. I don't know what you mean by better/cheaper--a 2.8l Powerstroke conversion would be better for that dough. There basically isn't a build up that I can think of doing that would run 10K before installation. But if you have that kind of money, then go for it.

As for using the 4.0 pistons, I looked into that and did some volume measurements--I will have to check my notes, but the compression started to border on 11:1 which was higher than I wanted to run--I wanted to stick to fuel that one could borrow on the trail and didn't want to carry around octane boost everywhere.
Quote:
Originally Posted by Oxcart13 View Post
Jon - I think you should consider the option of building up a 4.0/4.6 block. If done right, it will be just as good as your other options, and considerably cheaper. As an example, I bought a used 4.6 crank, rods, and pistons (22K miles), with new rings and bears from UK (via RPI) for around $800 to convert my 4.0 to 4.6.

For Phil's question, see attached. 4.6 on the left
I may be really showing my ignorance here, but I feel that a complete new plug and play 4.6 will be much more reliable, therefore cheaper in the long run. RPI may be pricey, but everything is balanced and put together by a guy that builds Rover 4.6s all day everyday. I am not saying that it can be done stateside on the cheap and be reliable, but RPI seems to know their stuff. If an RPI 4.6 cost $5k more and is as good as some say, then a Frankenstein 4.6 will cost more than RPI from the constant patching up.
As for the 2.8, yea that is tempting. I just wonder about down the road stuff like parts and DOT BS. I admit that I have never built an engine, thus the reason why I started this thread. I would rather learn here than in the shop. I have yet to drive a 2.8, but that 4.6 I drove had plenty of power.
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1993 NAS Defender 110 #375/500: Sold
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1991 Range Rover Hunter Green: Sold
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  #11  
Old January 25th, 2010, 01:07 PM
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That 4.6 motor that RPI builds in the UK was borne from the Buick motor that engine shops here in the states have been rebuilding for 30+ years. If you haven't already, poke around on aluminumv8.com. All I'm suggesting is you consider/research finding a suitable rover block, having it built up to your spec, and then weighing the pros/cons.
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  #12  
Old January 25th, 2010, 01:12 PM
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that 4.6 I drove had plenty of power.
Well, not compared to a Ford or Chevy Small Block. Those engines can be tuned to deliver well over 300 HP without too much effort for half of a Rover engine price.
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  #13  
Old January 25th, 2010, 05:25 PM
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I built a 4.6 for my '85 110 and it didn't cost me an arm and a leg, you don't need to go across the pond for everything. As suggested check out aluminumv8.com. Those guys helped me build a high torque motor thats putting out way better than the stock 220 hp and I'm using a 4bbl carb. The new LT77s has held up for 20k whithout issues.
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  #14  
Old January 25th, 2010, 05:33 PM
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Having been around a few of these, my suggestion would be to change as little as possible and still get the 4.6 you want.

In that regard, I would suggest a 4.6 short block, skimmed and rebuilt stock heads, a crower cam, a 4.2 RRC LWB ecu and whatever else new you want in/on the motor. There is no good reason to convert to serp. You need a very expensive front cover from a 94/95 DI or 95 RRC, new ancillaries, new fan shroud etc. and are making something that never existed in a Defender. Leaving everything but the block and chip and cam the same makes everything more understandable for repairs.
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  #15  
Old January 25th, 2010, 07:31 PM
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Ron--when you had your heads skimmed, how much did you take off? Do you know what it made your compression? Mine will be off in the near future...I may do a little tweaking!
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  #16  
Old January 25th, 2010, 07:37 PM
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I forget. If I were going to do it again I would just use GEMS heads or something else that did not need to be skimmed.
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  #17  
Old January 25th, 2010, 07:53 PM
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I read somewhere (can't remember where I'm afraid) that not all 4.6 short blocks can take a distributor. Is that true ? Anyone know which ones will/wont ?
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  #18  
Old January 25th, 2010, 08:04 PM
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It is the front cover, not the block that is the issue.
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  #19  
Old January 25th, 2010, 08:12 PM
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So if I am reading this correct if you have a GEMS 4.0 all you need is pistons,rods, rings, crank, cam and bearings and you got yerself a 4.6?
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  #20  
Old January 25th, 2010, 08:29 PM
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Quote:
Originally Posted by evilfij View Post
It is the front cover, not the block that is the issue.
I did a little more reading and apparently it's the oil pump that isn't always transferable. Anyone throw any more light on this one ?

The reason I'm asking is because I'm thinking of taking the short block out of my son's 93 disco to put in my NAS 110.
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