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Thread: Engine number ?

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  1. #1 Engine number ? 
    frequent forum contributor Club Member
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    I freely admit to being puzzled by the engine number of my 'new' Marlin Roadster.

    I was told it was an MGB engine BUT the number on the alloy plate does not seem to fit.

    [Block casting has 1800 on it.] Twin carbs are SUs from an MGB.

    Aluminium plate is embossed [from underside ?] with number '486733 ER550**' , held down by 2 drive-rivets in typical Leyland fashion, and has AD externally stamped later below it.

    AD may possibly stand for Autosprint Developments [who used to tune B-series] ?
    (there is a scribbled note with the car that says it has an Autosprint Developments big-valve head ...)


    Was expecting a number beginning 18V ...

    ETA ** represent numbers.
    Last edited by marlin1984; 18-09-2019 at 11:03 PM.
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  2. #2 Re: Engine number ? 
    frequent forum contributor Club Member stevejgreen's Avatar
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    A photo of the plate in question would help.
    B series blocks were used in numerous vehicles and were frequently swapped around, particularly Marina engines being transplanted into MGB’s as the cranks were perceived to be better.

    There is also a common misconception that every B series 1800 is in fact an MGB engine.
    There are many differences, from 3 to 5 bearing crankshafts, to exhaust manifolds, ancillaries, to the engine back plates, starter motors,, clutch, flywheel, etc etc.
    Through history, with numerous personal inputs, it’s difficult to tell whether the engine number actually relates to what you really have. The block may well be Marina, but the head could be MGB, or even Land Crab in origin, let alone all the other BL/MG marques that used basic B Series block.
    You could well have a bitza engine, that people call for convenience an MGB engine, even though the complete ensemble of parts from fan at the front to flywheel and clutch at the back, does not conform to a single identifiable defined vehicle.
    MOC member since 05/97
    1984 Marlin Roadster SWB.
    1800TC, Unleaded ported head, stage 2 cam. Ford Type 9 gearbox, Dolomite Sprint rear axle fitted with MGF disc brakes.
    Three core radiator, Renault Clio vented front discs.
    The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.

    Loads of Marlin Reference can be found documents here or there.
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  3. #3 Re: Engine number ? 
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    Thanks for that Steve. Will try and take a picture tomorrow - weather permitting.

    [Have removed the metal fan already as too far from rad to have any effect. There is a Kenlowe fitted.]
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  4. #4 Re: Engine number ? 
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    Looking closely at an enlargement of the picture I took - I reckon the third digit is NOT a 6 - but rather more likely a G.

    Still not sure if that helps tie down the origin of the block ...

    It may help - because 48G733 engines were apparently Gold Seal MGB engines - so maybe I will be telling DVLA.
    Last edited by marlin1984; 18-09-2019 at 11:05 PM.
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  5. #5 Re: Engine number ? 
    Club Member lil_red_roadster's Avatar
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    This page might help if you haven't seen it already (lots of other good stuff in there too)...confirms that 48G733 is a Gold Seal replacement for an 18V MGB engine. Lots of MGB forums out there and this question seems to crop up quite frequently.
    Marlin Roadster, LWB...1860 B Series + Ford Type 9
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  6. #6 Re: Engine number ? 
    frequent forum contributor Club Member stevejgreen's Avatar
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    Quote Originally Posted by marlin1984 View Post
    Looking closely at the picture I took - I reckon the third digit is NOT a 6 but more likely a G.

    Still not sure if that helps tie down the origin of the block ...

    It may help - because 48G733 engines were apparently Gold Seal engines - so maybe I will be telling DVLA.
    The numbers after 48G were a code for the bore size etc.

    I don’t see a picture!
    MOC member since 05/97
    1984 Marlin Roadster SWB.
    1800TC, Unleaded ported head, stage 2 cam. Ford Type 9 gearbox, Dolomite Sprint rear axle fitted with MGF disc brakes.
    Three core radiator, Renault Clio vented front discs.
    The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.

    Loads of Marlin Reference can be found documents here or there.
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  7. #7 Re: Engine number ? 
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    Hi Steve.

    No photo yet ... I'm still trying to edit via Flickr. But it keeps on saying I'm using an 'unsupported browser' and inviting me to download the latest version of Google Chrome.

    Done that but still asks again and again and again.
    I'll sort it.

    ETA [ 19/09] Given up on Flickr.
    Last edited by marlin1984; 18-09-2019 at 11:07 PM.
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  8. #8 Re: Engine number ? 
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    Quote Originally Posted by lil_red_roadster View Post
    This page might help if you haven't seen it already (lots of other good stuff in there too)...confirms that 48G733 is a Gold Seal replacement for an 18V MGB engine. Lots of MGB forums out there and this question seems to crop up quite frequently.
    Very interesting page. Thanks.

    One entry I simply don't understand > "February 2010: In practice Gold Seal engines have an 'E' or 'N' suffix letter as in 48G733E nnnnnn. The 'E' refers to an exchange engine, either fitted by a dealer or an owner. 'N' refers to an outright purchase i.e. no return of a faulty unit. "

    Seems like a dogmatic statement of fact . Perhaps it should read "In practice some Gold Seal engines have an 'E' or 'N' suffix ...." ?

    In practice - mine does NOT. It has neither 'E' nor 'N'.

    It does have a PREFIX to the engine number but definitely NO 'suffix letter after 48G733'.

    Seems even 'experts' can get it very wrong!
    Last edited by marlin1984; 18-09-2019 at 11:10 PM.
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