TDI to V8 conversion

pauldaf44 · Sep 18, 2014

I'm currently working on a project to convert my 1998 Disco 1 auto to petrol v8 power. The reasoning is simple the TDI in it is knackered and I don't like diesels anyway. I'd be much happier with a petrol engine so far I can see 3 viable options 3.5 with carbs 3.9EFI or TVR V8, but somehow I think cost my squander the latter option. So really how much difference would I see between 3.5 or 3.9?

So far this is what I can think will be needed to convert but please feel free to tell me if ive missed something.

V8 Exhaust System
New Fuel tank, electronic pump and fuel lines.
Engine wiring loom.
Bypass immobiliser or fit one from a petrol car.
Gearbox adapter plate?

Also what legal loopholes do I need to jump through to keep it bonafide road legal?

D90mitch · Sep 18, 2014

Matching V8 ECU. Don't know heaps about the V8 but I was speaking to a few people at a car show a little while ago and all said the 3.9 is the best to drive, fair bit more powerful. I've only driven my 3.9 disco very briefly and it certainly feel's powerful

When me HD springs arrive and I can take it somewhere, I can have a proper drive then...

You'll need a V8 radiator as these things get warm!

Only downside to the 3.9-4.6 Rover V8's is the slipped liner issue they sometimes get if poorly maintained or have overheated in the past etc, which requires the block to be milled out and newer 'top hat' liners to be placed (have a lip on the top so can't slip).

It's hard to tell it between that and head gasket.

As for road legality, as far as I know it's just sending the Engine replacement number to the DVLA to say it's had a different engine put in.

norseman · Sep 18, 2014

How refreshing to hear of someone converting TO a V8! I'm not able to offer any advice re. the conversion, only some V8 experiences from my RRC's (four) ownership. All 94mm bore RV8's are prone to the dreaded liner-slip & having owned both 3.9 & 3.5efi examples (both auto) I have to say that any performance differences, despite what the stated figures tell you, in normal day to day driving is negligible & the smaller engine is slightly more frugal. The simplest of all of course would be the 3.5 on carbs but I've no experience of how that set-up drives & believe it's heavier on fuel than the efi version.

D90mitch · Sep 18, 2014

3.5 Carb - 134BHP
3.5 EFI - 155HP
3.9 EFI - 182HP

srtgray · Sep 18, 2014

norseman said:
How refreshing to hear of someone converting TO a V8! I'm not able to offer any advice re. the conversion, only some V8 experiences from my RRC's (four) ownership. All 94mm bore RV8's are prone to the dreaded liner-slip & having owned both 3.9 & 3.5efi examples (both auto) I have to say that any performance differences, despite what the stated figures tell you, in normal day to day driving is negligible & the smaller engine is slightly more frugal. The simplest of all of course would be the 3.5 on carbs but I've no experience of how that set-up drives & believe it's heavier on fuel than the efi version.

The 4.0 in my D2 Auto is more economical than the 3.5 in my 110 Manual was, despite the heavier vehicle, auto 'box and use of Cruise Control. The ECU has better control of the fuel than the carb ever did.

pauldaf44 · Sep 18, 2014

To be honest ive got a TDI for local runs and such but find it a touch gutless for heavy towing work. Economy wise I cant see an LPG V8 being much worse when towing 3 ton than 300TDI. Add to that the benefits in comfort and ease of driving the V8 auto seems a better option for long distance towing which is what I want the vehicle for.

If I can find one id love to fit a 4.2V8 like we had in our old Vogue LSE. It wasn't terrible on fuel, Dad used to get 23mpg on petrol and 21mpg on LPG and the 200bhp was rather pleasant. Im presuming that the disco 300tdi auto box will just bolt onto the V8 engine or do they have different bell housings for petrol and diesel cars?

D90mitch · Sep 18, 2014

pauldaf44 said:
To be honest ive got a TDI for local runs and such but find it a touch gutless for heavy towing work. Economy wise I cant see an LPG V8 being much worse when towing 3 ton than 300TDI. Add to that the benefits in comfort and ease of driving the V8 auto seems a better option for long distance towing which is what I want the vehicle for.

If I can find one id love to fit a 4.2V8 like we had in our old Vogue LSE. It wasn't terrible on fuel, Dad used to get 23mpg on petrol and 21mpg on LPG and the 200bhp was rather pleasant. Im presuming that the disco 300tdi auto box will just bolt onto the V8 engine or do they have different bell housings for petrol and diesel cars?

As far as I know, the shaft on the gearbox is a different size (length) where it mates to the engine so that will need to be changed.

Snowey · Sep 19, 2014

There are a few mot failure v8s to be had cheap. I must admit if I were considering such a project I think I would go down that route. That way theoretically I would know I have what I need.

D90mitch · Sep 19, 2014

I might even just be a lot easier to buy a V8 disco you know. They're very cheap these days. A good one can be had for very little! Mine was dirt cheap as it was an MOT failure and failed to start (Turned out to be an earth as fired up when bumped). And as far as I can see, no rust!!!!

TDI to V8 conversion

pauldaf44

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D90mitch

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norseman

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D90mitch

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srtgray

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pauldaf44

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D90mitch

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Snowey

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D90mitch

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