Which v8 for mgb conversion?

Hey - someone with the same idea! (see my previous post). Because of its light weight it keeps the character of the original car, whereas the thumping great Rover/Buick lump changes it completely. It fits easily, transmission can be a problem as so few Daimlers had a manual gearbox - although I'm sure some research would show what gearbox it was and what would be compatible. I'm assuming you would not want the much more common auto box.

The exhaust problem I mentioned earlier was purely a matter of plumbing, i.e. how to get the pipes past the structural bits and out to the back. But there are plenty of people out there who would custom build something.

Could have been a very decent development of the MGB if the prats who owned it at the time had shared their few remaining brain cells.

Geoff MacK

Light weight?? The rover V8 engine is one of the lightest around, it probably weighs around the same as the horrible, sluggish, underpowered, fuel-guzzling, smog-producing cast iron "B" series engine! Badger.

That surprises me. It was a cast iron block. The Rover V-8 - with all accessories and exhaust manifolds is only slightly lighter than the 'B' engine similarly equipped, and the Rover is all ally.

What needs altering, suspension wise? Can't be for the weight. Perhaps to clear a standard sump?

Rocking horse s**t springs to mind. ;-)

Snag is it was an extremely expensive engine to make. The Rover unit cheap, with more power and torque.

Well, I'm assuming if you get a Vitesse engine it will be complete with the EFI parts. The EFI loom is complete so not difficult to use on the 'wrong' vehicle. Fitting the high pressure pump and fuel lines would be the most difficult part. But of course Rover made a much later injected B, so it should be possible to get some clues on the easiest way from that.

That would suggest they were very little 'faster' than a carb SD1. The truth is very different. Did you do an exhaust gas analysis to make sure they were running rich enough at full power? Many don't.

My real point was that the 3.5 is a sweeter engine, despite the 3.9 being oversquare.

"Faster" is down to a lot more than simply a peak bhp figure, the efi engine has a lot more power in other areas than just at peak, mainly due to the far superior design of inlet manifold as opposed to the fact that it happens to be injected. The engines both had adjustable fuel pressure regulators fitted, to ensure that they weren't running lean at full throttle (a typical rover trait to aid economy!) and were running at lambda 0.98, just slightly rich.

I'm not going to try and argue the point with you Dave, as "sweeter" is a personal opinion as to just how you prefer the delivery characteristics to be. My personal opinion is that the 3.9 with a mild/fast road cam, running efi, is every bit as nice and has similar delivery characteristics to the earlier 3.5 vitesse engine, but with more power and a slightly flatter, higher, torque curve. Badger.

If it's of any help, a few points from when I fitted a RR V8 to a SD1 box for a kit car:

1. The RR flywheel/clutch is just large enough to foul the bellhousing, and the clutch itself is much bigger with a deeper cover. IIRC the splines are different.
2. The RR flywheel is *much* thicker, so does without the spacer used by the SD1, between the flywheel and crank flange. Without this spacer, mods to the clutch actuation system are required, but it will run.
3. A spigot bearing is required to fit into the end of the crankshaft for the gearbox shaft - there are different sizes. All need to be soaked in oil for a day or two before fitting.
4. There appear to be considerable differences to manifolds, carbs and water pumps - in particular some pumps are about 6" longer than others, which would probably be a factor in a MGB. If you want a low bonnet & carbs, try Strombergs - these are much lower than SUs.
5. I keep hearing about reliability problems with 3.9s & 4.2s - head/block cracking. Make sure you get a good one, if you really want to

- because of these problems, they are expensive S/H.

Personally, I'd go for a 3.5, the later the better, with fuel injection and electronic ignition. (Make sure the back axle is in good nick.) Use a modern electric fuel pump, and make sure there is a filter in the line. Unlike modern engines, these V8s use high flow / low pressure oil systems, so stick to good old 20/50 unless you *know* the engine requires something else. Overheating might be a problem, IIRC there was a trick to get a high capacity radiator by fitting a 5 row core to MGB tops & bottoms, but I can't remember the details.

HTH, Dave

PS - Unlike modern engines, they will NOT self-prime the oil pump after a rebuild - you have to fill the pump with vaseline or somethig similar first. Very annoying if you forget, especially if it starts first time. (Not that I've ever had that happen....)

I noticed you said - 'I'd say go for a known running 3.9 and convert it to carbs' - but why not stick with EFI ?

Because most don't understand - or want to learn - about electronics and electrics. The idea about going back to carbs is ridiculous - especially with the current price of petrol. So saying, if you want to play about with non standard cams, etc, then carbs are a better bet.

One big reason that I stick with DCOE Webers and the Ford crossflow in my Seven is the sound it makes. The induction roar from that motor at full chat is music. And it's still quick enough, with a deft hand, to dance around all but the most exotic and expensive of the competition.

Dave - can't answer some of your earlier points - memory not that good - but just wonder why it was an expensive engine to make? Looked pretty simple to me. Also, really going out on a limb here, wasn't it basically four Triumph parallel twin engines (same designer) mated? Understand that the Rover engine had more power and torque - damn well should be, with a litre more - but why cheaper?

Final thought - how about the larger version of the Daimler lump - 4.5 V8 - as ditched by Jaguar because it was embarrasingly better than the XK - now that would really make an MGB go!

Geoff MacK

Or pick a make of engine that has an ECU with mapping data and how to's available on the Internet. Japanese

sites. one but sadly the prime source linked to bysr20tuning has been under reconstruction for a very long time and hasnow disappeared. The ROMEDITOR program is available fromboostcruising site above.http://www.sr20tuning.com/theoryandpartsrequired.html Mess with your ECU maps? You can with a Niceun by Nissan.

Or fit an ECU that can be programmed like Emerald M3D. But that costs a lot more than an Eprom programmer and a handful of chips.

RPI know how to roll thier own chips for Rover V8's if you search hard enough there just may be some info out there on the net.

It may have shared some design clues with that engine, but of course few, if any, common parts. I dunno why it was said to be expensive to make - perhaps better quality materials needed or complex machineing?

Well, it was designed for ordinary mass production cars where unit costs and profit margins are much tighter than on a Daimler.

Plus the fact they wanted to make their own V 12.

But given the fact that both those engines and tooling probably still existed by the time it became BL, there must be a reason why they were allowed to die, and my guess is still cost.

The MGB's chassis struggles to handle much more power than standard. After all, Jaguar had gone over to IRS *before* the B was introduced. And fitting a heavier engine would do nothing to help this - as was proved with the C.

And the RV? whatsit that was introduced in the '90s which was basically a B with a Rover V-8 was slated for its handling.

There is that, but trying to jet etc DCOE carbs so they are spot on across the range ain't easy. No problem to get max power, though, so more suitable for a track car than road use.

You need a totally different high pressure pump for injection systems. Make sure you get one with the secondhand engine.

So what would be involved in converting a carb engine to EFI ?

and given the reported problems in mating a 3.9 to an SD1 box it seems to be the opinion that using an original box with an original engine is better.

So what would be the preferred option out of these two - 1. A RR four speed manual 3.9 or, 2. a 3.5 SD1 5 speed manual . I'm sure I have come across a four speed manual SD1 somewhere, perhaps I am imagining it.

Somebody else noted that a 5th gear may be redundant ?

Sorry, forgot to mention the point that it is easier to find an EFI range rover than an EFI SD1.

To be absolutely correct, for a 3.5, you need to make sure the cam and ecu are matched (either both Rangerover or both SD1), and if not present, grind buff or file the injector spray pattern clearances into the inlet ports. (Easy, just match the gasket.) Std 3.9's are all efi anyway.

There is NO problem mating a 3.9 to a manual 5-speed box, just make sure the crank has the correct spigot bush (pennies and easy to replace) and use the sd1 flywheel/clutch assembly.

1. no such beastie, 4-speed manuals were all 3.5. Use the 3.9 with the 3.5 sd1 box, clutch, flywheel etc. The only reason for the bigger clutch in the landrover products is the harder work when towing etc etc.

Only if you don't use it! Badger.

As regards the 3.5, I'd not do it. There are other mods than just the injection.

As far as I'm aware it's a simple job.

No V-8 SD1 had a four speed. The P6 did, but that's a dreadful box, and the chances of finding one in good condition small.

Depends on use.

I don't know that I would even consider a V8 swap for an MGB today, since Japanese fours are so cheap and may make all the power you can handle in this car.