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MG MGB Technical - help with engine identification numbers please

Ok, so i received a heritage certificate for my UK 1972 (May) BGT a few weeks ago. However it states that my car originally had engine number 18V-581-F-H/2292.

I now find that my engine number is 18GB/U/H70765

Obviously some discrepancy there :-< I have no record of the change in engine, but i do know that engine work (including rebore) was carried out in 1987, just not to what engine....

So questions:

1) Can anyone help identify the meaning of the numbers a bit better? I have looked in the Moss catalogue and understand most of it i believe, but a second opinion would be nice.

2) What is the age of the 18GB engine - would be from an older car (i though 18V was the latest engine type). Can anyone tell me more of this type engine?

3) How do i go about finding out when the engine change took place? The V5 shows the 18GB number, so one assumes that the PO must have notified the DVLA of the change - can i get this info from them?

TIA as always

~PHIL
Phil

Oh and the chassis number begins GHD5 and ends in G if this helps/assists

Cheers! ~PHIL
Phil

Phil. I can provide little information since we do not need to record engine numbers and engine changes with US registrations/vehicle titles. My LE is, to my certain knowledge, on engine number 4.

Yes, your 72 should have an 18V engine. The fact it has an 18GB engine indicates an earlier engine was installed. The 18GB was the first five main bearing engine, used from Oct64-Nov67 according to Clausager. It seems that all markets got the 18GB engine, but, after the US began to require emissions controls, various different engines were used for various markets.

18GB/U/H70765 would indicate an 18GB type with a manual transmission (U) and high compression (H). 70765 was the engine number and the numbers ran from 101 to 91175, so yours was towards the end of production rather than towards the beginning.

Do not know exactly what you want to know. The most common reason for changing engines is a thrown rod (with number 3 being the most common), needing a rebuild and the other engine was available at a lower price, etc. The 18GB was used in the Mark I cars with the three syncro gearboxes, so the back plate would have been changed to the later Mark II type to allow the use of the pre-engages starter with your four syncro gearbox. Les
Les Bengtson

Phil,

Your 18 GB engine number dates from Feb 1967 - at least the block might be that age - the internals and head could be any age!

It is not unusual to find hybrid engines - especially from some rebuilders. I suspect that a PO simpy exchanged the original engine for a rebuilt one.
Chris Betson

The whole reason this came to light on Phil's car was that I was struggling to get an oil pressure reading on starting my freshly rebuilt 18V engine despite obvious oil to the filter and rockers.
I had a suspicion my oil gauge pipe was incorrectly located as there was a blanking plug above it, immediately next to the oil cooler pipe, so I asked Phil to pop around so we could check, thinking he had an 18V engine. However, it was 18GB. But, the oil pressure take off was next to the cooler pipe, unlike mine. I swapped the gauge take off and the blanking plug around and immediately got pressure on the guage.

But, I noticed in the Haynes manual variations on where the gauge is connected. Any thoughts amongst the experts out there what the blanking plug was for and why it might be swapped on different engines?

TIA
Martin

Thanks guys

I did want to know the age of the "new" engine, thinking it was from an early car.

I have a reasonably extensive history with the car, and an engine rebuild occured in 1987, as i have receipts for new pistons, crank regrind etc. However no mention of new block...

Seemed odd to me that one would retrograde to the 18GB engine from an 18V, but i suppose one uses what one has to hand. At least i don't feel too bad about putting the next engine build on another "new 18V block now! :->

The final question, would the DVLA release the date which the V5 changed the engine number details? Its more for idle curiousity than anything....

~PHIL
Phil

Hi,

My 1971 MGBGT has an 18GB block. I dont know of any engine change, just a rebore of the original motor.

Is the 18V a better block than the 18GB? What are the differences?

Cheers joe
joseph phillips

Yes the DVLA will relise the history of your car as long as your the registered owner and they have any details. I understand that they charge for this service these days. Have a look at thier web site for deatils..or phone them!
I was lucky they managed to have all of my B's previous owners on record.
Cecil Kimber

Martin,

The oil pressure take off is in the same place on all B series blocks.

The tapped hole below it - which has a blanking plug on later engines and a brass tap on early ones - is a block water drain, which usually gets blocked solid by rust!

Joe,

There are detail differences - the 18V has cut outs in the cyls to clear the late head exhaust valves and the oil gallery is shorter to allow a mechanical fuel pump to be fitted ( non MG applications) and for the later engine mounts. Early engines have main bearing studs rather than bolts and conrod/piston assemblies are different - but all are interchangeable. Otherwise there is no real difference in all the 5 bearing blocks.
Chris Betson

Chris, thanks for that, and there I went pumping oil into it from a can to see if it was clear, so now I can expect to see traces of oil in my £15 long service life coolant! ARGH! Never mind, I have a core plug that needs reseating, so may was well drain and refill. (anybody call them Walsh (sp?) plugs like we did in South Africa?)
Is it possible to retro fit the drain tap?

Thanks again, Chris.
Martin

Yes, they are Welch plugs.
Chris Betson

...and yes, you can fit the early drain tap!
Chris Betson

On a late engine I installed the eary style rear water tap. The block had been cleaned in a hot tank and the radiator was new. I checked the tap and it was working. After about 1000 miles I checked again and it was blocked. I think they are just for looks. At least it is easier to find if you want to remove it and drain the block.
Barry
Barry Parkinson

This thread was discussed between 29/06/2003 and 01/07/2003

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