Posible acquisition

[HairyDave]

I am negotiating the acquisition of an 1800 Roadster. It is from someone I know well but where do I find the VIN or chassis plate on a T reg car and how do I tell the difference between an 1800 TC Marina and MGB engine. I has 18V engine number prefix. That's it for now. Dave

[stevejgreen]

Re: Posible acquisition

If it has a Marina bell house and the triumph style gearbox it's likely to be totally Marina.
The basic engines are the same, but front and back plates are different. The biggest clue is that the MGB had an electric fuel pump.

more info here or there and here or there

[HairyDave]

Re: Posible acquisition

Cheers Steve, Hopefully it comes home on Friday so I will find out all the details, it has a big red lump with a Marlin plate on the Ally rocker cover ad a pair of SUs.

[stevejgreen]

Re: Posible acquisition

Every possibility that you have a TC there.
Over 40 years and people swapping ancillaries and parts about you won't know what you have really got until you start serious investigation. For instance, is it an unleaded head, only visible with the head off, unless someone stamped UL on one of the tabs.
Equally, the twin SU's were used in various cars with different needles, again not visible, you just hope that if a tag is fitted that it hasn't been modified.
But, if it's a runner, leave well alone.

[HairyDave]

Re: Posible acquisition

At the moment it is a bit of a sad non runner, first job clean it , look a it ,and lots of photos. Then get it running, it was when it was left ? years ago. See where we go from there. I used to work on the principle of 'If it ain't broke fiddle with it till it is' now I tend to leave well alone. Dave

[Harry]

Re: Posible acquisition

Hi Dave, the MGB gear box is a larger unit than the Marina / Truimph box, and the Clutch slave cylinder bolts to the casting 5/16 UNC if I remember correctly, as for the engine, as Steve said it's hard to tell after 40 years of tinkering, however MGB engines had forged steel cranks, where as the cheaper Marina engines were fitted with cast Iron cranks. I'm at Coedpoeth near Wrexham by the way.

[lil_red_roadster]

Re: Posible acquisition

I'm not sure all MGB had forged cranks - according to one article I've seen there were 3 different sorts over the years for the 5-bearing unit, 2 forged and 1 cast, with the Marina being different again (cast).
Interestingly I seem to recall Peter Burgess recommending an early 18v Marina crank due to it's better balance.
Worth noting that the MGB gearbox input shaft does not fit a Marina crank...some Marinas may have had an insert in the crank which can be removed to accommodate the MG 'box (which might suggest some factory "parts sharing")...but I don't have anything other than anecdotal evidence for that.

[stevejgreen]

Re: Posible acquisition

My guess if it has a triumph box is that it's all Marina.
A head casting number would help, a bit, but as with swapping parts the B series head in many guises found itself on Mgb's Marinas and even Morris 1800's so often got swapped around in search of larger valves. Add to that the unleaded issue, and heads become a little unpredictable.
Even crankshafts are difficult to tell as I have seen three different counterweight/web designs, and of course there is the spigot bearing diameter.
Another MGB Marina variant is whether the oil filter is top down or bottom up. But Marinas changed around the MK2 period, so that's no hard and fast indicator either.
All of this is pretty academic. If the car has not moved for a few years, coils, HT leads, fuel pumps and the various seals could be suspect, with carbs corroded stopping the Pistons from rising and falling.

But if it starts and runs, everything else can wait.

[dcunn]

Re: Posible acquisition

Look forward to more details and pics, tell me the reg (PM if you prefer it) and I may have some info for you
Meantime these pics will help if the chassis (kit) number is in the usual place
Good luck - and enjoy the rebuild Rgds DC

[Harry]

Re: Posible acquisition

Hi all, yes I believe the later MGBs used the Marina engine, the MGB gearbox will fit the Marina engine as long as the rear plate and spigot bearing are also replaced. I had read that the MGB forged steel crank was stronger than the Iron cast crank but the cast crank had better wear characteristics. Not sure how important this would be on an engine of less than 100 hp ?

[HairyDave]

Re: Posible acquisition

I was planning on a Berli but this Roadster came up which is why I'm a bit wrong footed. I had a fair bit to do with the A series and Marinas including an OHC O ser , but the B is unknown territory More info once I get her home on Friday. Thanks for the info. Dave

[stevejgreen]

Re: Posible acquisition

Extract from Peter Burgess, How to Power Tune MGB 4-Cyl Engines
So you have to read this from an MGB perspective

Crankshaft
With the standardisation of parts, the early B's steel crankshaft was replaced by a cast iron one. Surprisingly, the cast crank is the superior of the two, being better balanced and with better wear characteristics.
The best cast crank is the flat sided one to be found in 18V engines from 1971 to '74 (including the Morris Marina to 1974) which is fitted with a removable spigot bush because of the smaller diameter input shaft in the Marina gearbox). The later Marina Crank has large rounded counterweights and the wrong sized spigot bush. In order to use these in an MGB it's necessary to have the end machined out to take the larger bearing for the input shaft.

[Harry]

Re: Posible acquisition

That's a handy bit of info Steve, I must have had two later engines to tinker with as the MGB and Marina spigot had the same OD but smaller ID on the Marina engine spigot. Sorry about hijacking your post Dave.

[lil_red_roadster]

Re: Posible acquisition

Extract from Peter Burgess, How to Power Tune MGB 4-Cyl Engines
So you have to read this from an MGB perspective

Crankshaft
With the standardisation of parts, the early B's steel crankshaft was replaced by a cast iron one. Surprisingly, the cast crank is the superior of the two, being better balanced and with better wear characteristics.
The best cast crank is the flat sided one to be found in 18V engines from 1971 to '74 (including the Morris Marina to 1974) which is fitted with a removable spigot bush because of the smaller diameter input shaft in the Marina gearbox). The later Marina Crank has large rounded counterweights and the wrong sized spigot bush. In order to use these in an MGB it's necessary to have the end machined out to take the larger bearing for the input shaft.

Cheers Steve...I really must rescue my copy from the father-in-law..!

[HairyDave]

Re: Posible acquisition

At last I have a Marlin,Roadster more in need of heavy TLC than a rebuild (I think). ith bit of luck have included a picture. Maybe 2 the same. More later.Dave