V8 conversion planning

V8 conversion planning

Whilst the restoration of my car’s bodywork edges slowly onwards, I thought I’d write an update on the plans I’ve been making for upgrading the drivetrain later on. As the post title kind of gives away, these are now going to include a Rover V8 conversion!

Back when I started the project I intended to stick with 4 cylinders, but started to read up on the various performance upgrades that were available for the B-series engine (larger capacity, upgraded cam etc.), with the goal of achieving slightly more spritely performance. Anyway, one thing led to another, and before long I found myself devouring Roger Williams’ V8 conversion bible (“How to Give Your MGB V8 Power“), and coming round to the idea that a V8 conversion was not necessarily as daunting as I’d always believed.

The Rover V8 is an iconic engine, a mainstay of many of my most favourite classic cars (Range Rover, the Rover P6 and SD1, and of course, the factory MGB GT V8 itself), and putting one into my car has always been a bit of a dream. A V8 conversion is still definitely not something to be taken on lightly, and there is obviously way more to it than just swapping the engine and gearbox, but reading the book did give me the confidence to think that with enough research and careful planning that it would be a project well within my abilities.

I’m starting with the slight advantage that I have a rubber bumper bodyshell, which already has some of the production modifications used by the factory V8s to facilitate the conversion (revised steering column, inner wings and engine mountings, for example), but not all of them (relocated radiator mountings, only found on later r/b models). So there would be some bodywork modifications still required, including potential other changes to the gearbox tunnel and inner wings depending upon my gearbox and exhaust choices, but since pretty much every bit of sheet metal on this car seems to be getting attention this does not daunt me!

When thinking about what kind of performance I would ideally like from the car, my ambition would be for it to be powerful and more exciting to drive than before, but certainly not stray into the realms of ridiculous BHP numbers that make it impractical. Appearance-wise I still plan to have the car look as superficially factory standard as I can keep it, whilst incorporating a few modifications along the way to make it easier to drive and live with – the intent is that it will be something of a sleeper. The idea of a seemingly bog standard rubber bumper GT which pushes out 200+ BHP or so was becoming irresistable. So, decision made, why not start with trying to find an engine…

Having finished reading the book, my initial shopping list started with the 3.9 litre variant of the Rover V8 (as fitted to later RR Classics and the MG RV8), which seemed to be the best compromise between performance, availability and ease of conversion, which I would mate to an LT77 5-speed gearbox as fitted to the Rover SD1 (there are other options, but I like the idea of sticking to the Leyland era bloodline). I had initially discounted the later 4.0 and 4.6 engines as fitted to P38 Range Rovers, thinking that converting them from their distributor-less engine management configuration to something more traditional that would work in an MGB was more than I wanted to take on, but the more I researched the more I found it was a path many others had taken without too many issues, so I included them in my search.

After a few weeks of looking for something suitable (and affordable) it was clear that the P38 engines were by far the most plentiful type available – and many of them can even be acquired with a free Range Rover still attached! – but finding one that wasn’t likely to need a full rebuild proved a bit more difficult. Eventually I struck what sounded like gold when I found a Gumtree listing for a 4.6 engine that completely fitted the bill: recently fully rebuilt, and previously fitted to an SD1 Vitesse so had already been converted to work with a distributor. Without much hesitation I called the seller to discuss further: an obvious Rover and V8 fanatic, he had rebuilt the engine himself after taking it from a tired P38, and had only covered about 2000 miles in it before deciding to restore the Vitesse back to factory 3.5 specification. I was convinced enough, so hit the road to go and check it out and hopefully take it home with me.

Obviously I wasn’t able to see the engine running since it was not in a car, but it turned freely and the internals all looked as pristine as described, so I took it on trust that all was well and worked out a deal. The seller was retaining some of the SD1 parts (such as the sump and oil strainer) for their own car, which was a shame as they are exactly what is needed for an MGB conversion and I would have to source them myself later. They did however include the all-important SD1 timing cover, and a good condition SD1 flywheel (which seem fairly hard to find these days), so all in all a pretty good result.

Could use a bit of a clean at this point, but isn’t it marvellous!

Safely home and on the stand I was able to do a more thorough inspection. The outside of the block was a bit grubby, but beneath the rocker covers and within the block everything looked very clean. The heads had been rebuilt, and the bearings, piston rings, camshaft and other parts had all been replaced in the rebuild, with a new duplex timing chain fitted. I’ll do a more thorough stripdown and inspection a long way down the road when I get a bit closer to fitting this to the car, but I’m happy enough for now.

As you might be able to see from above, the front end needs some reconfiguration to fit into an MGB. It had an SD1 water pump, which needs to be swapped with the “short nose” version as fitted to the P6 and factory V8 to clear the MGB radiator. Similarly the crank pulley on it seems to be the original Serpentine pulley from its’ Range Rover origins, so that needs to be swapped for the short V-belt pulley also fitted to the P6 and factory V8. The front cover is perfect for fitting into an MGB, but the oil filter housing at the bottom of the picture will need to be replaced with the remote oil filter base utilised by the factory MGB GT V8 to avoid the oil filter fouling the front crossmember.

So with the engine procured the next thing I needed to find was a gearbox. The LT77 box that I had intended to look for seems pretty readily available on eBay etc., but given that some of these units are now well over 40 years old and parts supply seems to be a bit sketchy it felt risky to take a punt on a used one like this. The conversion guide also suggests that the additional power of the 4.6 engine (particularly with some extra tweaks I may yet make) may be more than the LT77 can safely handle, so I needed to find an alternative.

That alternative for me has come in the form of an R380 gearbox, a later evolution of the LT77, which can reputedly handle the extra power comfortably. This gearbox was commonly found in 4WD form in Land/Range Rovers, but was also fitted in 2WD form to the MG RV8 (replacing the LT77 mid-way through the production run), so there is another neat bit of MG lineage there.

The 2WD variant seems fairly rare, and I believe it’s difficult/impossible to convert a 4WD box, so I was quite lucky to find this newly rebuilt example on eBay.

With engine and gearbox both now safely in the garage, I’ve spent the last couple of months on a bit of a treasure hunt, trying to track down all the various other bits and pieces I will need to bring this project together. It’s been a bit of a fun distraction from the occasionally tedious bodywork restoration in many ways, and helps to maintain my enthusiasm for the project when that side of things gets a bit challenging!

I’m sure I’ll expand further on all of this in future posts when I get closer to fitting some of these parts, and I’ll definitely do a post on some of the very hardest to find items and how I sourced them, but here’s a few of the key bits I’ve collected so far.

Clockwise from back: R380 gearbox, 2WD gearbox bellhousing and fitting kit, clutch release arm, SD1 gearbox mount, SD1 gear lever, gear lever remote assembly and fitting kit

The gear lever remote assembly is common to the LT77 and R380 and is required for the MGB installation, but has a slight issue in that the gear lever position does not quite match the expected position in the MGB gearbox tunnel. Common solutions to this include modifying the SD1 gear lever by cutting it and welding a plate between the two sections to shift the vertical position, or using a cranked gear lever as originally fitted to the MG RV8 (and good luck finding one). The other alternative is to cut a few centimetres out of the middle of the remote housing itself to make it shorter and then weld it back together, so that the standard gear lever sits slightly further forward when fitted. The item I managed to find is one that has already been modified in this way, so I’m hoping that this will all come together correctly without further adjustment some day in the distant future!

That’s a bit of a taster of things to come, and there will be much more to write on this topic since a V8 conversion of this nature is going to change pretty much everything: brakes, suspension, electrics, cooling, fuel system. But in the meantime, I have a little bit more bodywork to get on with… *sigh*

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