Any info on the p38 GMC Diesel conversion?

I have an option on a very tidy low mileage 2001 4.6 Vogue in the what I consider to be the right colour combination but the Thor engine is boiling over in it. I took a spark plug out of it and sure enough it looks like its been steam cleaned so i guess the liner has gone in it.

As the car is so clean it might be worth repairing but I am a veg oil user and I have no desire to start going to fuel pumps, especially not these days. For me I would need to fit a diesel in it if I was to use this car.

I already have a p38 with a good standard diesel motor but a tired gearbox, and Ive read that the gearbox would need to be changed so to do that conversion becomes less feasible to me.

Also, we all know about the 6.2 GMC conversion that has been built but I dont know what had to be done to achieve that. At first glance that sounds like the direction I would go in.

Does anyone know what was done to get that lump into a petrol P38 and make it work reliably?
Can anyone suggest any other sensible petrol to diesel/veg oil engine conversions for the P38?

BMW M51 would be good.

jimllshiftit said:

I have an option on a very tidy low mileage 2001 4.6 Vogue in the what I consider to be the right colour combination but the Thor engine is boiling over in it. I took a spark plug out of it and sure enough it looks like its been steam cleaned so i guess the liner has gone in it.

As the car is so clean it might be worth repairing but I am a veg oil user and I have no desire to start going to fuel pumps, especially not these days. For me I would need to fit a diesel in it if I was to use this car.

I already have a p38 with a good standard diesel motor but a tired gearbox, and Ive read that the gearbox would need to be changed so to do that conversion becomes less feasible to me.

Also, we all know about the 6.2 GMC conversion that has been built but I dont know what had to be done to achieve that. At first glance that sounds like the direction I would go in.

Does anyone know what was done to get that lump into a petrol P38 and make it work reliably?
Can anyone suggest any other sensible petrol to diesel/veg oil engine conversions for the P38?

Click to expand...

Pretty sure you can use the HP24 gearbox in your 4.6 with the diesel. @ovalandrover has one in his diesel, I think. So no problems there.

Yes, a guy from Blackpool living in the States dropped a 6.2 lump in his but it wasn't straight-forward. Took him 3 years, IIRC. Have a look on rangerovers.net as that's where the thread is.

Hmmm...................... I think ive talked myself out of this GMC idea already.........

I was hoping that using an engine so simple as an NA V8 would just require power to the stop solenoid and starter motor, an adapter plate and away it would go with a few less electronics to worry about. No such luck!


If I pinch the M51 I already have and drop that into the cleaner car what issues is that likely to raise? I read something about the engine wiring harness is different after 97 but it didnt elaborate on what needed to be changed. My diesel is 97 and the "new" car is 2001.

Grrrrrr said:

Yes, a guy from Blackpool living in the States dropped a 6.2 lump in his but it wasn't straight-forward. Took him 3 years, IIRC. Have a look on rangerovers.net as that's where the thread is.

Click to expand...

Back in the mid 'nineties I drove a Chevy Blazer of military origin in Belgium & was very impressed by it's performance, but then it was a factory built vehicle. I would imagine the all-iron GMC lump would be far too heavy for a RR & do nothing for the vehicle's handling characteristics.

What plug was it that was steam cleaned? Boiling over doesn't necessary mean block/liner failure - it could just be the head gasket, which if you are mechanically able to take on a full engine swap, then a head gasket swap would be a walk in the park for you.

Granted, it *could* be a liner/block problem - but they aren't nearly as common as people make out, and I would have thought that more investigation than just pulling a spark plug is needed to condemn a block!

I haven't yet seen an engine conversion into a P38 that hasn't required a LOT of additional work/machining/modification, which is fine if you have the time/resources to make things yourself - but if you are having to get bits machined/custom made then it soon becomes a pretty expensive task... probably more expensive than a new top hat linered block or even short engine to repair what's already in there (if you go that far into it).

I've read about the GM conversion, but that was a lot longer and more drawn out that i expected it to be, given his original plans, and progress. There was another guy who put an LSX engine in (again in the USA) but that also required custom mounts, brackets, adapters, and I think a different inlet manifold to make it fit under the P38 bonnet. I gave him some pointers on getting the electrical side of things working, as he was trying to run it partly with the GEMS ECU and partly on the LSX controller.. I also saw an article on putting a V6 diesel in the P38, but again it was about £6K to do it, as the engine mounts needed to be moved, and the gearbox crossmember cut and re-welded. Though from what I read in the article, it all ended up working as it was supposed to.

I'm not trying to discourage the idea, but unfortunately it isn't something that seems to be widely done - because it isn't a simple swap... If you do go the engine swap route, then do a writeup on it!

**EDIT** If you were to swap the M51 into the Thor vehicle, then you would need to change a fair number of bits - engine loom for one. Also the Diesel is 'drive by wire' and doesn't have an accelerator cable - but rather a position sensor on the pedal - so the pedal box would need to be swapped to allow this. Also, and associated wiring for that would need to be run in . The radiator on the Diesel vehicles is also different to the Thor petrol, so would need to be changed, along with the A/C lines as the AC compressor is on the opposite side of the engine on the Diesel. I am sure there are some other differences too..

Well, it all seems like a good idea in principle but scratch the surface and it becomes more effort than its worth.

As my diesel one it currently running so well, although it looks atrocious, I think I would be better off spending my time and money tarting that one up than taking on such a massive engineering project as I originally suggested.

Thanks for your support, but this engine swap is not for me....................

You might as well whip the heads off and take a look. Might be an easy, reasonably cheap fix.