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I need some advise please, i own a 94 D90 NAS since 1998. The 3.9 is tired, i am seeking for some advice for a new motor. I am seeking more power as the 3.9 is under powered by mine standard. I have some questions

1. Replace with a 4.6 long block, i understand the cost is not cheap ? Does anyone have a ball park cost ? Is the extra 30-35hp make a noticible difference ? ( i have 33 inch tall tires which did slow down the acceration fromthe stock 31 inch ) can i still use the top end ? Injectors, intakes ECU ???

2. Any other solutions ?

3. Small block Chevy conversion ? 300hp is nice, but the originalness and possible collectibility is shy me away the GM conversion !

Please offer me your .02

Or link to forums that may have covered this discussion.
 

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I notice the difference in having a 4.6 in my 1994. I'd do it. If I had to do it all over again and I had the money, then I'd do the LS swap (Plenty of info on this forum). That would be my #1 choice. My #2 would possibly be a 300 tdi or 2.8 diesel. But again, you are talking many thousands of dollars.

You can pick up a 4.6 pretty cheap at a junk yard and swap over or rebuild to a nice level. Still get 13-15mph, a little more torque/horse, but I definitely feel the difference.

If I did go the 4.6 route, I would swap at your 1994 v-belt distributor driven oil pump cover and go with the crank driven oil pump of the serpentine set up. better oil pressure, better life. Yes, you have to swap over a few ancillaries, but it is worth it. The distributor driven oil pump is a joke once it is worn in. 4-12 lbs of oil pressure sucks. My idle now lives around 20 and just goes up from there...and that is good for an engine.
 

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I was in the same position you are last year. My 3.9 was very tired and needed a rebuild. I decided to best route for me was sticking with the 3.9, but putting a cam, dual row timing chain, and high flow heads on it. It kept the stock appearance and all the stock parts, but runs very well. I ordered the engine from Turner Engineering, got it in 3 days, and swapping was very easy. I don't have any objective measurements of performance, but it holds its own with a Forerunner in a drag race, FWIW.
 

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If you had a 4.0, then it's a heck of a lot easier to go the 4.6 route. But if you want to keep the rover engine just because and for sentimental value, then maybe you should consider getting a 4.0 and have it rebuilt and stroked for 4.6. Just pick up a tornado chip to get the full effect of the 4.6.

I'm going the 4.0 (NAS 97) to 4.6 because I do want to keep the rover engine. If I do the import route, then I'd definitely swap in an LS3.
 

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LS conversion if you are staying with a gasser. Use the search function, there is ample reading on the subject.
 

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I went from a 3.9 to a 4.6 with a crower performance cam and the tornado chip. Noticeable difference. If you want to stay "original" but crave more power, this is certainly the way to go... It's also very costly.
 

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I went from a 3.9 to a 4.6 (D & D cam, lipped liners, mild attention to ports, 5.0 injectors) in my 94 D1, (which has serpentine belt driven accessories). Very pleased with the difference in power/torque. Not sure I ever checked fuel economy- big tires, gearing changes, lots of heavy equipment, massively lacking aerodynamic efficiency. Don't have the disco any more, but still have the engine....
There is a guy who purchased a 4.8 from :
Rover V8 Engine - V8 Performance Engines - Land Rover Engines - Jaguar engine Off road racing and he is fitting it this week. I was supposed to do the install, but my schedule got jammed up and he found someone closer to home who could do it sooner- so I don't have any firsthand knowledge of the quality of the product.
 

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Your question is a valid one but when you tally the votes my money says you will be equally puzzled. The best recommendation I can give is find a well carried out 4.6 set up and drive it. The incremental differences between 3.9/4.0 to 4.6 is something you should really judge by the seat of your own pants.

IMO the guys serious about V8 performance and reliability and not worried about a green oval on the manifold are doing LS3's.
 

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I went from a 3.9 to a 4.6 (D & D cam, lipped liners, mild attention to ports, 5.0 injectors) in my 94 D1, (which has serpentine belt driven accessories). Very pleased with the difference in power/torque. Not sure I ever checked fuel economy- big tires, gearing changes, lots of heavy equipment, massively lacking aerodynamic efficiency. Don't have the disco any more, but still have the engine.... There is a guy who purchased a 4.8 from : Rover V8 Engine - V8 Performance Engines - Land Rover Engines - Jaguar engine Off road racing and he is fitting it this week. I was supposed to do the install, but my schedule got jammed up and he found someone closer to home who could do it sooner- so I don't have any firsthand knowledge of the quality of the product.
I miss making popcorn on the backseat passenger floor.
 

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Engine swap

I'm right behind you. My engine is tired as well. Where are you planning on having the work done. Please keep me posted thanks.
 
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