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4.6 into 3.9 Disco

Tech Talk for Rover owners.

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4.6 into 3.9 Disco

Post by up2nogood »

Has anyone done this conversion and how much drama was it? My vehicle runs the LT77 (?) manual g'box and i don't really want to mess with that set up due to the level of mods required.
I 'spose it's either that or a gen 3 GM V8, but obviously this will need the gearbox to be fitted as well, along with a different computer, etc, etc, etc.......But I don't really want a slush box or to go to too much trouble.
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Post by Evan »

R380 gearbox and LT230 transfer i would think.
E
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Post by up2nogood »

So you think it would be better to pinch the entire drive train from a 4.6 rather than try to bolt the 4.6 to the existing gear?
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Post by Evan »

As far as i know which is not to much the 4.6l will both straight upto your R380 in the disco (not TDi as they use a different bellhouseing on the R380) with no issues as all except maybe electonics.

Evan
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Post by red90 »

It will be fine with the LT77.
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Post by up2nogood »

Ah ha!

Does anyone know if the 4.6ltr has the same head and block heights to the 3.9ltr?
Just want to figure out if the inlet manifold will interchange to save too much electrical bother. If the 4.6 is a bore and stroke increase without increasing deck height it will be a lot simpler.
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Post by Evan »

Bore is the same
Stroke is longer.

No idea is the blocks are the same, see my question about 4.6 rods and crank into a 3.9l block in another thread.
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Post by Bush65 »

Block height of 4.6 is same a 3.5 - no need to change manifolds. I replaced my 3.5 with a 4.6 short motor - used 3.5 heads timing cover etc and LT77.
John
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Post by red90 »

http://www.rpiv8.com/faq-conv.htm Have a read at this link for some information. If you search around on the web for Rover V8 or Buick 215, you'll find a ton of specific forums and mailing list for this engine.
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Post by up2nogood »

Red, you are my hero!

Thanks for the link, it answered just about all the questions.

Because most of the 4.6 engines came out in HSE's they were almost all (or maybe all, correct me if I'm wrong) autos.

Will the 3.9 flywheel bolt to the 4.6 crankshaft and will it need to be balanced with the crankshaft? (Yes, I know it's good practice anyway!)
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