P38A Diesel to Petrol (1997) - Conversion

Morning all,

I´ve had my P38 DSE for just over a year now, bought it from a scrap-dealer and have somehow (through much cursing and many grazed knuckles) manage to bring it back to life.

I live in Germany, and despite replacing just about everything that was needed to get it the equivalent of an MOT pass out here, it turns out that in the long term it seems to have been in vain. Germany seems to be leading the fight against diesels, and as such - my vehicle tax has just gone up to a staggering €864 per year....and even once i´ve paid this monsterous sum - I can´t "visit" any of the main German cities due to their already strengent anti-pollution laws.

So i´m considering trying to change my P38 to a petrol (4.6 with LPG)....i know everyone is now most likely thinking the same thing - just buy a used petrol... but let me explain:

My car only ever had one owner (a State Owned Forest Commission) who spent plenty of money strengthening the original chassis (total weight officially in at 3,089kg!!)...which of course the diesel engine just loves! And i´ve done just about all of the aesthetic repairs plus a lot of general maintenance up until now.....HEVAC, entire brake system, steering system, internal electrics, tasteful upgrades etc...

Does anyone have any tips, suggestions or perhaps even experience of doing something like this? I´m aware of the obvious things (new fuel tank + lines, BeCM, ECU etc)...

Would be very appreciative of any tips or hints or thoughts that people might have.

Cheers in advance

Rory

holy crap rory!!! Thats undertaking i wouldnt like to do personally!! Thats a complicated affair i would think..

Can't you just change the badge?

BECM can be kept - but would just need to be told it's petrol, and not diesel... that's probably the easiest part of the whole thing...

Some of the things you would need to swap other than what you've already mentioned...
Gearbox (the 4.6 used the 4HP24, rather than the HP22 the diesel used - and the bellhousing, and torque converter are different diesel - petrol)
Gearbox ECU? (I think they are different diesel - petrol)
Gearbox Loom? (again, think they might be different between diesel and petrol vehicles)
Engine ECU, Loom, possibly fusebox (as the petrol had different part numbers - though it would probably be easier to keep the diesel fuse box and then take the wiring you needed from there and splice it into new engine loom)
Pedal box (Diesel uses electronic throttle, whereas the petrol is cable driven)

I'm sure there is more - but it is somewhat of an undertaking to do! If you are serious about doing it, then I would look at buying a petrol vehicle as a donor vehicle, so that way you have all the bits you could need - and then it would be a case of just swapping them over..

He might have a manual box? Some 4.0 had a manual box too, didn't they? So that would be relatively simple.

I've been considering the same thing for similar reasons in the UK but my need isn't as urgent ... yet!

is the hevac unit compatible?

Mark Piercy said:

is the hevac unit compatible?

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Yes, all it does is send an AC request and receives an AC grant from the engine ECU if it is allowed to run the AC compressor.
The wiring is obviously different between petrol/diesel vehicles (and might come under the fuse box realm, depending on year - with the compressor harness upgrade and all that on the petrol models)

But the HEVAC controller isn't differentiated by petrol/diesel - only model year/VIN number.

Grrrrrr said:

He might have a manual box? Some 4.0 had a manual box too, didn't they? So that would be relatively simple.

I've been considering the same thing for similar reasons in the UK but my need isn't as urgent ... yet!

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he wants a 4.6 they didn't have the manual as an option

4.0 did but rare ain't the word!!!

funrover said:

he wants a 4.6 they didn't have the manual as an option

4.0 did but rare ain't the word!!!

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If 4.0l was available with a manual box then I bet it'd be a straight swap for the diesel that used the same box. Having said that, @ovalandrover managed to shoe-horn a HP24 gearbox in his oil burner so it can be done. I forget if there is an oil pump to swap over but I think the props might be different?

Grrrrrr said:

If 4.0l was available with a manual box then I bet it'd be a straight swap for the diesel that used the same box. Having said that, @ovalandrover managed to shoe-horn a HP24 gearbox in his oil burner so it can be done. I forget if there is an oil pump to swap over but I think the props might be different?

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yeh it was an option for very early 4.0s

Def get a donor vehicle with right bits. Will save lots of grief on finding parts for the swap. Just need to find a low mileage one on eBay with a bent or dented body.

If you're going through that process, I'd consider dropping in a more reliable V8. You'll be throwing a lot of time and money at your current vehicle, might as well go for an engine that won't chew through headgaskets and slip liners for fun.

+1 a Rover 4.0/4.6 is a big gamble especially with all the work involved with converting. I'd imagine most donor P38 V8's on the verge of scrapping are due to engine troubles anyway.

martynv8 said:

+1 a Rover 4.0/4.6 is a big gamble especially with all the work involved with converting. I'd imagine most donor P38 V8's on the verge of scrapping are due to engine troubles anyway.

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But a rover engine is near enough a straight swap. I think the 4.0 Thor might actually be a better bet as the security is more like the diesel and I think it has the same gearbox.

There is a guy on RangeRovers.net who shoehorned a 6.2l chevvy in there but it wasn't straight-forward and took him 3 years, albeit part-time around his work but who isn't?!

Grrrrrr said:

But a rover engine is near enough a straight swap. I think the 4.0 Thor might actually be a better bet as the security is more like the diesel and I think it has the same gearbox.

There is a guy on RangeRovers.net who shoehorned a 6.2l chevvy in there but it wasn't straight-forward and took him 3 years, albeit part-time around his work but who isn't?!

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The 4.0l also uses the same gearbox doesn't it?
Just think that risking all that work to put in a stock Rover V8 could all end in tears & misery, but thats just my experience. Think the Overfinch P38 use the 6.2 chevy

donor vehicle or not route, youre going to have to do a strip an rebuild of a V8 before you drop it in.. there's little point to going to so much work with an unknown engine. head gasket, main bearings, front cover.. it'll be easier to do on a stand than in situ.

also youll need the ancilliaries and pipework and harnesses as the V8 and diesel have them in different places.

a donor vehicle will be the easiest and cheapest route as you'll see where everything needs to go. got for the Bosch/Thor engine, not the Lucas/GEMS..

.. and you'll need full fat diagnostics

What about a 3.5 on carbs. No engine management or slipping liners to worry about!

Wazzajnr said:

What about a 3.5 on carbs. No engine management or slipping liners to worry about!

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That was going to be my suggestion but how about stroking it to (I think) 4.3 litres? I knew a mechanic back in the 'nineties who did just that using a kit from 'Real Steel' & was very happy with the results, but he overdid it once when towing his trailer & blew the A pack on the slush-box

I have no idea how a P38 would work with a 3.5 on carbs.. I wouldn't be surprised if it wouldn't work without the sensor inputs to BECM and engine management modules.

Then if you did get it to work.. are you looking at a different gearbox and running gear ?

If you get past all that, you'll have a hideously slow P38 V8 with no torque that drinks fuel and thats without the added weight you're carrying, and being not a classic car, you may find yourself on the wrong end of emissions regs.

To me a 3.5 on carbs in a P38 is like asking a fat chick to sit on your face

ukadamwest said:

I have no idea how a P38 would work with a 3.5 on carbs I would be surprised if it wouldn't work without the sensor inputs to BECM and engine management modules.

Then if you did get it work.. are you looking at a different gearbox and running gear ?

If you get past all that you have hideously slow P38 V8 that drinks fuel and thats without the added weight you're carrying and being not an classic car you may find yourself on the wrong end of emissions regs.

To me a 3.5 on carbs in a P38 is like asking a fat chick to sit on your face

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Nothing wrong with that. I've learned to breath through my ears.