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  #1  
Old October 28th, 2013, 08:33 PM
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Tim Riccardi
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3.9 to 4.6 1995

I have searched on the net and still have many questions on the direction I should take.

I have a '95 D90 with a good, never overheated, 3.9. I have owned since 98 and purchased of the original owner, that is a good friend of mine.

The engine has just over 100k and is running good. The trans is not shifting into 4th anymore, so I need to at least change the trans. I also have a 4.6 short block. The plan was to just swap engines and use all the 3.9 sensor/crap.

But...I have been thinking of changing over to at least a 95 Disco serpentine belt set-up. Or a complete GEMS system. Is the GEMS or Bosch set-up easier than the other. I know the wiring is a pain, but I have as much time as needed. I don't know what 4.6 I have other than it came from a RR. I'm pretty sure it had a black 4.6 intake.

I have checked and can fine many Discos with blown head gaskets and can swap over everything, with my 4.6. I have to really think about changing to auto and go form there. I'm not tied to the manual trans, so could change to an auto. The only concern I have is the center console.

Thanks Tim
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  #2  
Old October 28th, 2013, 08:48 PM
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Originally Posted by boxerhips View Post
I don't know what 4.6 I have other than it came from a RR.
What year 4.6?
Those late 90's are pretty good; it's the '03-'04 Bosch 4.6 that is crap.
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  #3  
Old October 28th, 2013, 08:48 PM
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Bill Adams
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Repair the trans. The rest, fah. If you want the 4.6 for the extra ponies, you can get that from your 3.9 pretty easily.
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  #4  
Old October 28th, 2013, 09:06 PM
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If you are non serp now, that is the simplest set up closely followed by the pre OBD2 (ie 95) serpentine. I honestly wouldn't want anything to do with a later V8. Tons of complexity for no obvious benefit
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  #5  
Old October 28th, 2013, 09:24 PM
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Tim Riccardi
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If I went the serpentine set-up it would be with another disco to remove all the needed parts. There is one close to me for 1k that runs, runs smells of antifreeze. Does the PSP, and a/c connect from a newer truck. I mean does the disco stuff connect to the D90?

I have the 4.6 so it that or just use the 3.9. I just have to remove the trans and thought of just bitting the bullet and doing everything.

I guess I could sell the 4.6 and heads. I had the heads refinished( seats, springs ect.)

I just remembered the distributors vacuum advance in not working either, of course it might run better, lol. I think I have the base timing @ 10 now and it runs great.

Does anybody think the GEMS is a better set-up?
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  #6  
Old October 28th, 2013, 09:56 PM
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Quote:
Originally Posted by boxerhips View Post

Does anybody think the GEMS is a better set-up?
Yes.

------ Follow up post added October 28th, 2013 09:57 PM ------

Quote:
Originally Posted by JSBriggs View Post
4.2 is a direct swap. 4.6 takes a little work. You need to swap the front cover over, and there is a little bit of custom work (crank spacer or some such).
-Jeff
You can just use a cam timing chain gear as a spacer IIRC.
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  #7  
Old October 28th, 2013, 10:44 PM
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GEMS sucks.

Just swap the block. Sell the heads and reuse the 3.9 heads and everything else. I have a spare 4.6 block waiting for my 3.9 to go.
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  #8  
Old October 28th, 2013, 11:14 PM
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Originally Posted by o2batsea View Post
Repair the trans. The rest, fah. If you want the 4.6 for the extra ponies, you can get that from your 3.9 pretty easily.
Do tell...
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  #9  
Old October 28th, 2013, 11:24 PM
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How much do you want ?
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  #10  
Old October 29th, 2013, 07:39 AM
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Originally Posted by o2batsea View Post
How much do you want ?
All of it...
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  #11  
Old October 29th, 2013, 08:05 AM
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Bill Adams
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Originally Posted by Grover View Post
All of it...
Get out the wallet. You can expect that with moderate mods (rechipped ECU, gas flowed heads, cam, headers) you can get about 30% more out of your lump. If you want even more, then you are getting into boosted induction, nitrous, and exotic engine management.
The other way to go is with the Edelbrock carb and manifold and do away with EFI. This is always a tradeoff.
This all depends on your need of course, so if you are building an engine for off road, you'd maybe want to keep it at stage 1 and not go with forced induction.
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  #12  
Old October 29th, 2013, 04:33 PM
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Tim Riccardi
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Quote:
Originally Posted by evilfij View Post
GEMS sucks.

Just swap the block. Sell the heads and reuse the 3.9 heads and everything else. I have a spare 4.6 block waiting for my 3.9 to go.

Please explain why GEMS sucks? Is the Thor injection better. It seems 2001 Discoverys can be had for $1100, lol. These things have no value with a blown head gasket.

Why use the 3.9 heads, I thought they are interchangeable.
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  #13  
Old October 29th, 2013, 06:01 PM
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disclaimer: I am a luddite and this is a rant

14CUX is much better than GEMS which is better than "thor"

GEMS sucks because it is less reliable than 14CUX. GEMS was a solution to making an OBDII compliant land rover V8, it was not a good idea. They had terrible issues with carbon fouling on the valves. They also used composite head gaskets and stretch bolts which lead to head gasket issues. Things got worse with the thor bosch system in the disco II. Those ran way too hot guaranteeing head gasket failures. They also ate MAF sensors like candy.

14CUX is the best. It is a bit of a black art diagnosing faults with the system and there are some common issues (bad vacuum advance on the dizzy, TPS sensors that wear out, bad silver relays etc.) but it is a fundementally good system (as rover stuff goes) and the faults normally do not leave you on the side of the road and/or are easy and cheap fixes (ie keep spare silver relays in the truck).

3.9 heads fitted originally with metal head gaskets can be refitted with metal head gaskets to any block. The 4.0/4.6/very late 3.9/4.2 heads with composite gaskets are thinner to accomodate the composite gaskets. Ergo, I would reuse the 3.9 heads and fit metal gaskets.
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  #14  
Old October 29th, 2013, 06:15 PM
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Making a Bosch engine management system would be a lot more difficult than making GEMs or 14CUX work. I think you would need a lot of other modules from the DII such as the BCU. The BCU would not be happy without things such as power door locks. I don't know of anyone who has done a Bosch engine swap. GEMs is definitely doable, you just need to modify/make a harness for it.
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  #15  
Old October 29th, 2013, 06:58 PM
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Converting to GEMS on a 95 is a ton of work and a detriment.
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  #16  
Old October 29th, 2013, 09:48 PM
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If your 3.9 Is running well keep it. Hog out the heads and intake, install a Crower 230 and play with the timing . I woke up my range rove. It was cheaper easier and less invasive than a 4.6.
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  #17  
Old October 30th, 2013, 08:45 AM
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Quote:
Originally Posted by o2batsea View Post
Get out the wallet. You can expect that with moderate mods (rechipped ECU, gas flowed heads, cam, headers) you can get about 30% more out of your lump. If you want even more, then you are getting into boosted induction, nitrous, and exotic engine management.
The other way to go is with the Edelbrock carb and manifold and do away with EFI. This is always a tradeoff.
This all depends on your need of course, so if you are building an engine for off road, you'd maybe want to keep it at stage 1 and not go with forced induction.
Agreed. Letting the engine breath better will get ya more ponies...
Benching the heads and intake is free if you know how to do it and have the time.
Upgrading the cam with new tappets isn't that much $$$

Slainte,
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  #18  
Old October 30th, 2013, 09:15 AM
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Ron
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fix the trans and keep the good working motor.

You would spend a ton of time and money for 40 more horse?

as mentioned there are things you can do to the motor to get more hp, cam ,air cleaner , super charger, exhaust etc.....
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  #19  
Old October 30th, 2013, 12:28 PM
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Quote:
Originally Posted by ron View Post
You would spend a ton of time and money for 40 more horse?

as mentioned there are things you can do to the motor to get more hp, cam ,air cleaner , super charger, exhaust etc.....
A cam and lifters are going to cost more than the motor he already has. A supercharger is exactly a great choice for a Rover V8.
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  #20  
Old October 31st, 2013, 05:51 AM
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If you've seen the pile of junk 4.6's I have you'd stick with the 3.9. If you want to go 4.6 start with a new manufactured block. The rest are hit and miss.

You "can" tune to some pretty impressive levels with GEMS, but really not worth it. Theoretically you should be able to get something special out of it and I have spent some time with this (110 HI-Cap with tweaked GEMS 4.6 and 5 speed manual), and would not do it again. That truck ate Salisbury drive flanges like they were candy, and went really well but again.....not worth the effort. I'd rather drive than turn my Defender into a Disco nightmare.
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