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More progress! This time, I've got the wiring loom and battery cable properly fastened to the underside of the car. In addition, I've got the engine bay wiring loom fasted in properly and got the pedal box assembly in place. I've refurbished the heat unit but I can't fit it for real until I get new rubbers.

I've also made a repair panel for the inside of the rear quarter window at the base of the c-pillar. I found a template online that made this MUCH easier. I'll probably delay in fitting this until the car is back on its wheels.

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If you build it, they will come

Completed lots of little jobs over the holiday without much to show for it. I spent ages trying to get the wings and doors lined up properly. It's close, but I think I have to shift the hinges to make it perfect. I did manage to get a sneaky photo with the bonnet on though.

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If you build it, they will come

I bought some 8mm copper pipe today and spent some time this evening creating a fuel tank to engine bay fuel line. I've left the end too long so I can trim it accordingly once I know exactly where it needs to terminate.

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If you build it, they will come

I've not updated this thread for ages, but there hasn't been a lack of progress. In fact, I've done an incredible amount of work, but most importantly, I've changed direction on this restoration. I decided that I didn't want to restore this to the same condition as when it left the factory. I wanted to make something better, something more modern.

I know there's many that will be dismayed by such sacrilege but hopefully I can do it in a tasteful manner that will only add to the vehicle's appeal rather than taking away from it. I wanted this MGB to have a more modern, powerful, reliable engine with better brakes and better suspension. The shell is rot-free and very strong, so is a good base to build on.

I initially thought I'd refit the original engine and then update it at a later date once it was running, but I knew if I did this, then it would never get done. So, I took a leap of faith and sold the original engine. It went literally within hours. Apparently I sold it too cheap but least it went to a good home ?

So, what engine to replace it with? I had a few requirements:-

  • more than 4 cylinders
  • relatively modern with fuel injection, etc
  • would fit the engine bay properly without a massive amount of cutting
  • would look right
  • cost effective

My shortlist was as follows:-

  • Rover v8
  • Volvo straight 5
  • Volvo straight 6
  • Rover KV6
  • Jaguar AJ6
  • GM 54° V6 X30XE

The Rover v8 engine is tried, trusted, proven and is very much the safe bet. However, it's very expensive especially if you want a more modern variant, and after all is done, you're left with something that everyone else has done.

The Volvo option was a serious contender. However to make it work you need a sump, flywheel & manual gearbox from a Volvo 960 with an engine from any 5 cylinder Volvo. These parts are very rare and probably quite expensive. Even then, I'd probably have to get rid of the heater to get it to fit.

Rover KV6 has appeal by virtue of it belonging to the same stable as (sort of). However, it's a 90 degree twin cam v6 which means there's likely to be clearance issues. It's also got no obvious RWD route without resorting to a custom bell-housing solution.

Jaguar AJ6 is a 60 degree v6 and was also a serious contender. However, bonnet clearance is an issue without using a custom intake and the location of the oil filter provides a challenge with engine mounts.

The GM 54° V6 can be found in Opel/Vauxhall Omega, Vectra, and Calibra. It's a narrow angle V6 which means there's no clearance issues to the side. The only concern was the height. The 5 speed manual gearbox has ratios very well suited to an MGB 3.9 rear axle. The starter motor is in the right place and a rear drop sump is available (from a Vectra). It's also similar weight to the standard 4 cylinder but puts out 208bhp.

So, the GM option seems good, but a Vauxhall engine in an MGB? Well, if we consider that the Rover v8 was originally a GM engine as well, we can kind of say it's got heritage ?

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If you build it, they will come

The next thing is to remove the gearbox, clean it and see what challenges I would have fitting it into the MGB tunnel. The most obvious thing is that the gearbox is very tall at the base of the bell-housing just like an LT77 or R380. It's obvious that I'll need to do the same trick with the transmission tunnel to make room.

Whilst the gearbox is in the tunnel, I decide to offer up the Vectra sump to see what clearance is like on the cross-member. The fit is encouraging. It looks like it's going to fit, worst case with slightly notching of the cross-member.

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If you build it, they will come

When the engine arrived, it was filthy dirty and had this ugly great big front-drop sump which needed to be swapped for a rear drop sump before it would fit the MGB.

So, first job was to strip some parts off the engine which I wouldn't be needing. For example there was no way the standard exhaust manifolds would fit. The alternator wants to occupy the same space as the chassis rail so this too has to go (for now). The standard rear water pipe is too bulky. The wiring to the starter motor isn't needed because we can use the standard MGB wiring.

Next step is to clean the engine and to replace the sump and oil pickup pipe with one from a Vauxhall Vectra. Luckily, I had an old plastic sand pit that I'd been avoiding taking to the tip for years that I could use to catch all the oil & degreaser.

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If you build it, they will come

Back to the subject of gearbox fitment. It was obvious that I'd need to do the same fix to the tunnel that you'd need to do during a v8 swap. This is well documented elsewhere, but basically involves removing the forward section of transmission tunnel that droops down, giving more clearance to the gearbox.

I now have tons of clearance. Probably more than I'll need.

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If you build it, they will come

The engine that I purchased came with a wiring harness, ECU and key. Unfortunately there was a critical component missing - the immobilizer ECU. This means that as it sits, the engine cannot start. So, what do about this? Ultimately, I'd like to purchase a replacement ECU/Immo/Key combo (which is ~£50 on ebay) but in the meantime, I "fixed" the ECU so it doesn't need an immobilizer.

To do this, I firstly wired up the ECU with power & a check-engine light and saw that the check-engine light was pulsing at 1 per second. This is telling me that the ECU is alive but can't talk to the immobilizer. Next, I had to dismantle the ECU to expose a tiny 8-pin eeprom. This contains code that tells the ECU how to operate. I desoldered this eeprom and soldered it onto a spare Arduino prototyping board that I had. I could then write a quick "sketch" for the Arduino to read the contents of the eeprom, modify it and re-upload it back into the eeprom. I then desoldered the eeprom from the Arduino and soldered it back onto the ECU. Then, I plugged it all back in and powered it up. This time, the check-engine light did not flash and stayed on solid. There's another trick you can do to put the ECU into a diagnostics mode where it flashes the check-engine light to tell you what stored codes it has. This worked fine and it told me that the crank angle sensor was not working - almost certainly because the engine wasn't running!

So, now I almost certainly have a working ECU without immobilizer 🙂

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If you build it, they will come

Next next job to tackle was the rear axle. This got a complete rebuild of brakes & brake pipe. The diff cover was removed, diff cleaned out and the cover replaced with a new gasket. The axle was then put onto the car with brand new springs & complete fitting kit.

still to do is the straps & bump stops, the shocks and the handbrake cable.

Unfortunately, I don't have many photos of this.

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If you build it, they will come

And finally, to bring us up to date, last weekend was the day that we trial fitted the engine to see exactly what horrors we would find.

The engine & gearbox were bolted together and carefully lowered into the engine bay. Largely speaking, it went entirely according to plan. The engine sat back nicely with no fouling of the heads against the bulkhead or inner wings. The starter motor sits nicely in the same place as it would on the original engine. The gearbox fitted properly into the tunnel. And most importantly the bonnet did not foul on the engine, even with the standard cross-member in place. However, clearance was tight and I made the decision to relieve some of the cross-member to improve clearance. I do think, however, that this can be avoided if you accept tighter tolerances.

So, things to do:-

  • Engine mounts need to be made. It's unlikely that I'll use the existing chassis mount positions. These are just too far forward. Seems the V6 is shorter than the standard inline 4. I hope to do that this weekend.
  • The standard MGB gearbox cross-member pretty much fits although it needs modding to take the Omega gearbox mount
  • The coolant pipe that runs from the back of the engine to the front hits almost everything (steering, bulkhead) so this needs to be remade. Luckily there's quite a lot of clearance now that we're not using Omega exhaust manifolds
  • Exhaust headers need to be made from scratch. This is probably the biggest job. I'm undecided whether to take them inside chassis rails or out through the inner wing. At the moment, probably the latter but this remains to be seen

Who says you can't fit a modern twin cam v6 into an MGB?

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If you build it, they will come
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