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Before I started this engine swap, I checked the gear ratios of the Omega gearbox against the standard MGB axle to see if it would be tolerable. I found that the speeds at 3000rpm were almost the same as the standard 4speed overdrive MGB. You could argue that a torquier v6 could do with taller ratios, but hopefully it will drive ok.


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If you build it, they will come

I've had a few other expenses to pay for this month (other than the MGB) so the anticipated propshaft needs to wait another week. In the meantime I've got some small jobs finished.

  • The horrible Vauxhall gear stick has been removed and replaced with a diy gear stick made from steel tube & rod and a cheap Chinese gear knob that shows the correct gear pattern. It actually feels great and looks fine. It's a massive improvement on the std Omega one.
  • I've taken the v8 radiator to a local radiator repair specialist (Regal Rads) who soldered in a brass boss for me so I can fit a fan switch. Unlike the 4-cylinder radiator, the v8 radiator doesn't have one built in. When you have a v8 , it's in the thermostat housing on the engine itself. I bought a 105 degree switch which is the same as the Omega would have had. When I come to do the cam belt, I'll seriously consider fitting a cooler thermostat & a lower temp fan switch but for now, it's fine.
  • I fitted a relay to the fan circuit so that the radiator switch isn't taking the load of the fan motor. I've wired it so the fan switch will complete the ground pin of the relay.
  • I discovered the clutch master cylinder was weeping so I ordered a ยฃ5 seal kit from MGB Hive. It was straight forward to fit and has solved the problem completely. If you do this job yourself, remember to throw away the white plastic thingy that comes with the kit. You don't need it for a clutch master cylinder. Apparently you only use this if you're doing a brake master cylinder (uses the same kit).
  • My brakes wouldn't bleed. The front circuit was dry as a bone and try as I might, I couldn't get any fluid through. I tried to take apart the master cylinder to see what was up, but it was just completely gunked up -way beyond saving. Luckily for me, Peter Derbyshire had just replaced his master cylinder to try to solve an issue only to discover his old master cylinder was working perfectly. So I bought and fitted his old one. Brakes are now bled and the pedal is now relatively firm.
  • I won an auction on ebay a while back for a throttle cable. I think it was from a mk1 Cavalier automatic or something. I bought it because it had the correct fittings & looked long enough. It was only ยฃ3 delivered so I thought I'd take a chance. It did fit but it was a little bit too long so I removed it and shortened by 12". It fits better now and the throttle pedal feels more responsive.
  • I bought a 12mm to 10mm reducer from Car Builder Solutions so I could finally connect the vacuum pipe to the servo.
  • Bought and fitted a 6PK1440 fan belt & fitted it. I had to do a small amount of pulley alignment with some shims but other than that, it seems to fit fine.
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If you build it, they will come

I finally have a prop fitted!

It's a little different to what I first planned, though. The original idea was to use the flange adaptor that my friend machined on his lathe. This would convert the 3 bolt gearbox flange to a standard 4 bolt prop flange. However, some people put doubts into my mind about whether this would be a good idea or not. Logic tells me that the adaptor would be fine. People use these kind of adaptors on very high horsepower engines without trouble. The commercial ones are made from the same material and machined to the same tolerances as the one my friend made so really, my thinking was illogical.

However, the doubt wouldn't go away so I had to find a "better" solution.

In the end, I found several places that could make me a strong propshaft with a flange to bolt directly to the gearbox. The only problem was, they were about 50% more expensive than my local prop shop. However, these guys were experts in making bespoke props & I felt much happier with the advice I got from them than from my local prop shop. The vendor I chose in the end was Dave Mac Propshafts. They patiently answered all my questions & reassured my that they knew what they were talking about. The prop arrived about 3 days after ordering.

I fitted it tonight. It was a bit of a faff actually getting it in because clearance is tight, but it's in and it fits perfectly

My mind is now at rest, about this issue at least ๐Ÿ™‚

btw, any nuts & bolts you see in the pics are temporary!

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If you build it, they will come

Seems like I've not updated this thread for ages. However, I've not been idle - I've hit a massive milestone . I bought an MGB GT v8 exhaust from Moss & have spent the last week fitting it.

I had a little fun at first trying to work out how the heck the back box bolted on until I realized that the previous owner had replaced the rear valance and had not welded on the exhaust mount. So I purchased one & welded it in. Once this was in place, I could see that the v8 system was remarkably close to where I needed it to be. The pipe that crosses from one side of the car to the other lined up perfectly with the part of the sump that was designed to take an exhaust (when fitted in a Vectra). So, I spent a few evenings adjusting and welding the Y-pipe to make it perfect. The biggest challenge was the v-band flanges that I bought to join the headers to the system. They were cheap ebay items that were advertised as "45mm". What they actually meant was 1.75" which is almost but not quite 45mm. This meant that they almost but not quite fit my 45mm pipe. Some head scratching later, and I realised that I could heat them until they were glowing red & gently persuade them onto the pipe. Another challenge that I had was that the v8 exhaust had 40mm primary tubes and my headers had 45mm primaries. So, for now I've made some reducers to make it fit. 40mm is the bare minimum required for the engines power output and at some point, I'll cut & adjust to 45mm, but for now, it's working and I'm happy with it.

Next job for the weekend is to bolt the steering rack back in, fit the radiator, bolt the prop up properly, fit the handbrake cable, check fluids & then see if it drives (gently).

My goal was to have the car mechanically complete by the end of the year, and I'm not far off it!

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If you build it, they will come

Jobs today:-

  • Attach the prop with proper bolts
  • Fit steering rack & align wheels (by eye)
  • Fit radiator, fill with coolant & bleed
  • Fill axle with oil
  • Fit handbrake cable

I decided I wanted to bring the engine up to temperature to see how heat was managed. Everything was going well and then the engine started to make a weird noise just after the throttle was blipped. Sounds like something flapping about or rubbing under the cam cover. So, I took the alternator & cam cover off to expose the belts. Everything looked ok, so span the engine with ECU unplugged & everything seemed ok still. Started it again and noise is gone, but I did noticed that the cambelt tensioner was flapping about all over the place depending on rpm. Pretty sure it's not doing what it should be doing. Luckily, a cambelt change was next on my list of things to do. I'm pretty sure the engine is fine, and I'm sure a belt/tensioner change will solve it.

I also connected the MGB temperature gauge to the Vauxhall temperature sender & was rather pleased to see movement on the dial. I still don't know if it's going to read accurately, but at least it's showing signs of working.

If you build it, they will come

Well, after my scare with the cambelt tensioner failure, I thought I'd replace the cambelt & pulleys quick sharp! Luckily, my friend Nick had lent me his cambelt tools so it was quite painless to fit. This is now done & the engine runs great. We ran it for longer this evening for about 30mins, getting nice temperature & pressure into the system but still not hot enough to trigger the radiator fan. The MGB temperature gauge registered engine temperature but didn't go much above 1/4. However, so long as it registers something then I'm happy to call that "normal" for now. I might see if I can get any different temperature sender units & experiment until I find something that will make the gauge react normally.

Jobs remaining for this year:-

  • Sort handbrake. The proper rubber bumper handbrake doesn't fit my exhaust. The chrome bumper cable I have is too short so it must be for a banjo axle.
  • Put clamps on the exhaust
  • Finish the intake tubing with air filter
  • Tighten front suspension lower arm nuts
  • Put a nut behind the steering wheel, and I don't mean me ๐Ÿ™‚
  • Weld on o2 sensor bosses

I did try to put the ECU tacho pulse into the std rev counter but it didn't budge. I'll need to replace it with a modern unit. Rally Design do some cheap gauges that look half reasonable. Unfortunately, genuine Smith gauges are not justifiable.

What to do next year? Part of me wants to keep it off the road until it's resprayed and perfect. Another part of me wants to finish the paint temporarily with rattle cans & get it legal asap, then sort the paintwork as a project for next winter. Thoughts anyone?

If you build it, they will come

No updates for a while but I've been busy with stuff.

  • Handbrake is sorted. It now fits fine & avoids the exhaust. I created a new brake compensator bracket and fitted it at the top of the diff housing rather than the bottom. The cable now rides over the top of the exhaust at full droop.
  • Intake tubing is now almost complete. I ended up fitting the Omega's front variable intake valve but fabricated new piping to fit underneath it. Just need to get the air filter attached and it's good to go.
  • Fitted o2 sensor bosses and new o2 sensors. These are working and ECU seems much happier now
  • Had to fit a new crank angle sensor. The old one gave up the ghost. I fitted the cheapest one I could find on ebay (an Intermotor part). I'm told I need to use an expensive Bosch item but it's running well for now. If it breaks again, I'll get a decent one.
  • All suspension bolts are tightened with split pins. Grease nipples are greased.
  • Fixed a water leak. Turns out my heater matrix was broken. I soldered it up for now & pressure tested it to 20psi. If it fails again, I'll get a new one.
  • I've also FINALLY managed to get my laptop talking to the ECU. I can monitor fault codes and most importantly, I can monitor realtime stats. For example, the ecu can tell me the rpm so I can calibrate the speedo properly and it can tell me engine temperature so I can get the temperature gauge reading accurately.

I also managed to find some neat little electronics to make the rev counter work with my ecu. The same company also sell another box of tricks that will correct a gauge for any given input. For example, my temperature gauge reads a little low so I can use this to "normalise" it I'm going to have to buy a new speedo though. There's no cost-effective way to get my original speedo working with a speed-pulse output.


If you build it, they will come

Progress since last update:-

I brought the engine up to temperature again until the fan kicked in., monitoring with the diagnostic tool. It tells me that the temperature is under control at least in winter, in UK. The good news is that the temperature gauge reads middle of the dial when it's fully up to temperature (by luck rather than judgement). The bad news is that my heater matrix is STILL leaking. I tried fixing it again but it's beyond saving. I'll get a new one next week.

I've also spent some time on the intake system. The original engine had a complicated variable intake system which was far too big to fit directly so I scratched my head a LOT until I could come up with a decent way to packing the intake piping in the MGB so it actually fitted and looked like it might actually work efficiently. In the end, I decided that a system similar to the original factory system was the way to go. So I made it out of 76mm (3") PVC pressure pipe & flexible intake ducting. It works, it contains a variable intake valve, a MAF, an IAT sensors, it's routing cold air from the front of the car, and it will look MUCH better once I paint it black ๐Ÿ˜€

When I got my engine, it didn't come with an immobiliser so I hacked the ECU to remove it. This let me start the engine but now that it's at a stage where the car could grow legs and run away, I've decided to buy an ECU/Immobiliser/Transponder pack for safety. The immobiliser ECU sits behind the steering column cowl & fits around the ignition barrel. It was quite easy to wire in,ย  needing just power, ground, a wire to the ECU and a wire to the diagnostics connector. It's working fine and I've been able to both start the engine and also access the immobiliser from the diagnostics software. It also fits remarkably well on the MGB. Of course, to use this I now need a transponder key. I've found that a Land Rover Discovery key has the same key blade as the MGB but also allows a transponder chip to be inserted.

When I bought my car, it was already someone else's project. The PO had spent a lot of time, money and effort converting the rear of the car to chrome bumper. He'd also supplied chrome bumpers and grill with the project (not very good examples though). I considered changing back to rubber bumpersย  but given that I prefer chrome bumpers, that the car is already far from original and that the front of the chassis rails needed replacing anyway, I decided to stick with the PO's plan of changing to chrome bumpers. This will probably upset some people. So I got on with chopping out the final bit of rot on the car and making new box section. It's far from complete but I couldn't resist laying the bonnet on, tie-wrapping the grill on and putting the front valence on with a few bolts. The car is now the most complete it's ever been, for a short while ๐Ÿ˜€

Also, I've been trying hard to decide whether to get the car on the road asap or whether to keep it in the garage until it's absolutely perfect. I've been taking advice from my friends and the overwhelming consensus is to get it on the road this year and get it resprayed over the winter. So, next target is to get it MOT'd ๐Ÿ™‚

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If you build it, they will come

When you buy an ECU/Immobiliser/transponder kit for these engines, you'll rarely get any wiring harness with them. Luckily, I had the entire engine loom but didn't have any immobiliser wiring loom. So how to fix? I could have trawled a breakers yard trying to find the right plug but I'm too lazy for that. From a quick glance at the connector, I could see that it had 9 pins in-line, slightly offset from the centre line, in a rectangular socket with what looked like a standard 2.54mm pin spacing. A quick check with the digital calipers confirmed this. ebay turned up a JST-XH 2.54mm 9pin connector that looked like it might fit. It was literally a couple of quid so I took a punt. Luckily, it fitted perfectly.

The pinout is as follows.

  1. Alarm input - not used
  2. Engine management Light - I didn't connect this
  3. Not used
  4. Ground
  5. Ignition switched live
  6. Speed input - I didn't connect this
  7. ECU immobiliser connection - connect to engine wiring loom
  8. diagnostic line - connect to OBD connector pin 3
  9. Permanent live
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If you build it, they will come

Wow has it really been almost a month? I have been working on the car almost every day since without massive amounts of progress. It's amazing how much time stuff takes.

I've finished the repairs to the front of the chassis rails & have included mountings for proper chrome bumper brackets. I've also mounted the air filter properly, mounted the good (but cheap) grill I got from Stoneleigh, added sidelights/indicators and the lower valance.

I've also discovered that the 40yr old glue residue on the roof from the vinyl roof responds to white spirit so I'll be stripping that off over the weekend.

3 major jobs left - complete the sunroof, fit glass and headlights. Then, it'll be ready for MOT.

It's getting there, slowly. I hope to get it on the road this year & respray it over the winter/spring so it'll be perfect next year.

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If you build it, they will come