MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - mgb gt engine code

Hi looking for help with a engine code for MG BGT its a 1979 1800 with hif4 carbs and overdrive. The car has had a replacement Ivor Searl engine. So I dont know what the code is so I can set the ignition timing.
a goldup

Setting the ignition timing depends on which distributor you have and how it may, or may not, have been modified. To help you, we need certain specific information. If you look on the side of the distributor body, you will find a machined flat surface with some numbers on it. The top number is the Lucas part number, like 40897 (1966 MGB). This part number is the key to finding out which car the distributor is intended to be employed in. The bottom numbers show the month and year in which the distributor was manufactured. The vacuum advance control capsule is stamped with a three-figure numerical code that indicates its functional characteristics. For example, should the vacuum advance control capsule be stamped 4-12-16, this indicates that vacuum advance will not commence until the diaphragm has 4” of depression (in inches of mercury) and will attain its maximum ignition advance at 12” of depression, at which it will have advanced the ignition timing a total of 16 crankshaft degrees. They are also stamped with a seven or eight digit serial number that indicates its Lucas part number. If you will post this information, we can help you to get the ignition timing to where it needs to be.
Stephen Strange

Even the distributor number is no sure guide as any 25D4 or 45D4 can be fitted to any MGB engine. As an Ivor Searl engine it isn't likely to be any standard setting, I'd have thought, and quite possibly a non-standard engine. Furthermore if the engine was built prior to unleaded even the original data will probably no longer be ideal, as pinking is more likely on unleaded than the original leaded even if you go for 97, 98 or 99 octane. Without spending a lot of time on a rolling road to recurve the distributor for today's fuel and the current engine state the best rule of thumb you can adopt is to advance it just short of pinking at any combination of throttle, revs and load. This is for a high-compression engine by the way, which I assume this is.
Paul Hunt 2010

Thanks for your feed back.
I have no idea when the engine was fitted but have been told it is for lead free petrol. Having a look through the paperwork that came with the car a secondhand distributor was fitted a year ago so every thing is working against me on this one. I will ring Ivor searl to se if they can tell me what the serial number the engine replaced and then post the result with the distributor numbers. I have set the timing to 10% BTDC and it seams to run ok but has a bit has a habbit of popping back through the rear carb and runnig on when the ignition is turned off.
a goldup

Running-on is a 'feature' of MGB engines made much worse on unleaded, I've had to fit an anti-runon valve to mine. Popping back through just one carb could be a sticking inlet valve, but at the very least shows difefrences between the cylinders that shouldn't be there - assuming the carbs are setup correctly and the ignition system is working correctly.
Paul Hunt 2010

This thread was discussed between 01/05/2010 and 05/05/2010

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.