Blog : To MGB or not to MGB – that is the question!

Mike Humble

Despite being almost 50 years old, the GT shape still looks good.
Despite being almost 50 years old, the GT shape still looks good.

Ever said those fatal words “yeah, I can do that, no problem” and wished you hadn’t? It’s something we all say, all get burnt with and never ever seem to learn from. A very good friend of mine, who also supplied me with Project Partridge – aka the 800 Vitesse coupé, is a real Brit car man to the core, also owning a Stag and a 45 turbo diesel and, of course, an MGB. I know the car well, having spent a good few hours re-commissioning the vehicle after a period of lay up last Summer and enjoyed every moment.

Being a 1977 GT complete with topsy-turvy ride height and dodgem car bumpers, it has the necessary ingredients to survive in the modern world such as a tolerable ride comfort, long, lazy gearing and a charging system substantially more manly than a push bike lighting dynamo. Once a portly shape like myself grunts and groans into the slim cockpit, it’s a fairly decent drive to be honest so long as you can put up with your right shoulder and cheek rubbing up against the door and window pane.

I love the burble from the exhaust, the crisp gea-change (once the gearbox oil has warmed) and that lovely thump of long-stroke B-Series torque. Forget about the fact the bodywork crumbles away faster than a dissolving sugar lump, in my opinion, the fastback GT bodywork is still a pretty thing to behold to the eye and the car still drives okay providing the oily bits are in somewhere near good order. The 1798cc engine may be as refined as a drunken sailor but few plants are as simple to fettle or fiddle with.

In a fit of madness (some say) I purchased Keith Adams, Renault 18 – a car I find I love a little more every day, but this left with me with one small problem – no class steed to attend Pride of Longbridge with. The coupé only arrived here a couple of weeks ago and, besides, it’s sorned and there was little time to really go through the car like a bad pint so to speak, get it scrubbed clean, get it M0T-worthy and run enough to prove itself after a two year park up – then came a Baldrick-type cunning plan.

Recently, I visited my chum on the coast to fit some glow plugs to his non-starting Rover 45 and I mooted the idea of borrowing the BGT for a while, attend the show and service it for him at my cost as a thanks. This was all agreed but, after noticing there were one or two outstanding jobs, I could tell a little time would be needed with the tools before I even thought about the fair old jaunt from leafy Sussex to the once industrial powerhouse of Birmingham.

So I collected the car – and then the fun really started. Firstly, it had no power and it was pinking so badly that it required a gear change from overdrive top down to direct third even on a light gradient to keep the revs up so as not to cause any more of the pre-ignition which causes some serious harm if left undetected and unfixed. Light throttle usage gave some really grim flat spots and I could not believe how ill the car felt considering all the work I did on it last year.

After spending some time checking items like timing and point gaps, it quickly transpired the second-hand distributor fitted after my efforts last year was timed wrongly, not secured (you could move it with both hands) and the point gap was large enough to slide a slice of toast through. Still the car ran as sick as a dog with an upset tummy after those matters were put right, so further, more investigative measures were called for.

Nothing was left to chance. I even removed the rocker box and went through the valve clearances but, nope, all was good from last time but, once armed with a 13mm spanner, both carb locating nuts were in need of a good 3/4 turn – was this the culprit? Flicking the key saw no real improvement and a good road test still showed up some horrid pinking – what ever the matter was looked like some serious dismantling was required.

A compression test showed a cylinder down, though not enough to really make a huge difference but substantial enough to make me think a valve or seat may be burning out or otherwise faulty. Not having X-ray eyes, a call was put in to Eastbourne suggesting I might need to remove the cylinder head. Now, the car was fitted with an unleaded head a few years back and early castings were fairly prone to cracking between cylinders so it was worth a look to check.

Number 2 chamber (to the right) was choked with carbon - here is where the pinking came from.
Number 2 chamber (to the right) was choked with carbon – here is where the pinking came from.

Worryingly, when the bolts were slackened, some cracked loose as you would expect but one or two simply slackened with no real resistance. The head also stuck fast on a couple of studs so applying the two nut locking trick removed the offending studs and the head slid off like a knife through butter. Peering down into the bores I noticed No:2 had antifreeze wash out present – signs of coolant entering the bore making the cylinder crown cleaner than the others.

The combustion chambers looked fairly healthy except No:2 was caked in carbon which, when hot enough, contributes towards engine pinking. The head gasket showed slight signs of failing at the fire ring so out came the power drill and wire brush attachment along with some emery paper to clean up the bores, cylinder crowns and head. The rebuild process went well apart from the fiddly throttle and choke balancer rods that link the brace of HIF SU carbs.

One thing I did find out was how awkward it was to locate parts locally straight off the shelf. Last time I pulled a B-Series apart you could almost buy Spangles so, after drawing a blank with the local factors, I contacted those happy chappies at the MGB Hive up in Cambridgeshire and a head set along with a new thermostat housing arrived soon after. Older cars such as the MGB are in plentiful supply component wise – just be sure it’s all in hand before you do the job, it’s not as simple as running to the factors for a part.

Pistons, head and block cleaned up with the new gasket ready to go!
Pistons, head and block cleaned up with the new gasket ready to go!

After the coolant went in and a good scan around the engine bay for anything missed, the key was turned with much trepidation and one eye closed. The car ran better but not as sweet as I would have liked and, by the time I bled the cooling system, the heavens opened and I quickly got drenched. Getting rather bad tempered and fractious, the tools were thrown into the boot of the Renault and I ventured back indoors for a long soak in the bath.

Isn’t it funny how a rest and fresh view makes all the difference? This very morning I went back outside, re-torqued the head and had another tinker. Deciding not to hammer the car to Longbridge after some serious open heart surgery, I contacted the owner and arranged to deliver the car back to him. The journey was sublime to say the least, the power was back and there was no horrid pinking either. My friend drove the car when I arrived at his place and came to the conclusion it was better than it had ever been – the placebo effect, maybe.

It was a tough choice to make, run the car up to Longbridge and risk harming an engine that’s yet to settle back down to normality or play safe and keep the car local until the 500 mile head bolt nip and tappet check. With the car not being mine and concious of the fact it’s muggins here who cops the bill should it grenade itself, the latter was the only safe choice. My journey this year will be in a Volkswagen which is a personal shame really – just keep that between you and me.

Anyway, the BGT has been transformed and, even though I decided against a lengthy journey to Longbridge, I can return to my friend’s place next month to re-torque the head once more and set the valve clearances just in time for him to really enjoy some fine weather fastback driving – and who can blame him.

I might even be able to steal an extended road test… Just err on the side of caution!




Mike Humble


  1. Just looking at the photos of the “B” bring those 1970s memories back! As said before, a colleague of mine had a ’72 B GT as a company car in the same colour. Great times. The Rostyle wheels are the same I had on my Viva HC in the days before alloys became the norm…

  2. No2 will be using oil me thinks judging by the carbon.
    How come you didnt wide open throttle it and spray water into the carb for an instant decoke?

  3. If a car like the B is pinking badly and the timing is correct, please check the carb settings, as it may be running lean. I’m sure Mike checked these before pulling the head off… Once set properly any SU in good condition will not need constant tinkering and can be well left alone for a long time – years in the case of low mileage classics.

  4. As mentioned in the blog, the no:2 cylinder was showing signs of coolant ingress, the head gasket was ever so slightly failed between the coolant passage and fire ring.

  5. Love the Weslake shape of those cylinder heads, being a Mini man myself, it´s just like looking to the same part on bigger scale. This report is as effective in the B-series engine as it would be on A-series, thanks for sharing.

  6. The ‘Woollard’ on the front page should have been done Humble style, with a fag in the gob and a pint in hadn, with cat supervising. Glad you ‘fingers crossed’ fettled it Mike

  7. Has the distributor been changed for an unleaded advance curve version? If not speak to Aldon Automotive. I’ve fitted their distributors to my Riley 1.5 and MG midget for unleaded use – A big help.

  8. @Hilton D

    No that’s not the same colour. A blue ’72 would most likley have been ‘Teal Blue’ this B is NOT teal blue, a colour discontinued in ’74. This was replaced with ‘Tahiti Blue’ whihc was then repalced with ‘Pagent Mid Blue’ in around ’78. Both these later colours are very similar and quiet differnt to ‘Teal Blue’ which is a darker more greenish blue (and the colour of my Mg Midget). This car is alost certianly one of the later colours, as to which one I can’t say withough knowing when it was built

  9. A good read as ever Mike. Now I’m looking forwards to seeing the next chapter in Project Partridge 🙂

  10. I had one of these, it was a great car although my wife hated driving it. Mine was a Jubilee edition, I think No.147, although it was over 15 year ago I cant remember.

    I completely rebuilt the engine, re-bore and regrind. The cylinder head was skimmed and hardened valve seats fitted.

    Only 3 months after I finished the car, It was stolen which was bad, however on the same day my wife had a miscarriage. So in truth the loss of the car was put into perspective I don’t really remember much about it…..I guess, we had far bigger issues to confront.

    I did have a strange phone call about 6 months later, the voice said something along the lines of

    “That car that was taken, the MG, its been shipped to America.”

    They then hung up and Ive not heard anything since.

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