MGB Engine question

I have a 72' MGB with a mongrel engine - parts of a 69 / 72 / another (like originally an offset head with non-offset rocker pedestal - it was called spray lubrication of the rockers!)

The question is - was the 1800cc twin carb engine used in anything else such as a Riley or Wolseley? I've replaced the distributor, needles and set the timing but it doesn't like starting, the choke has little effect (seems to be weak), the exhast pipe looks black (rich). Balancing the carbs at tick-over runs weak in mid-range and rich above.

Fitting a Weber 45DCOE with standard MGB jets gave mid range very weak (almost undriveable) irrespective of timing

I seem to remember the old distributor (with badly broken lower body around the clamp) had an odd (non-MGB) advance number stamped on the fly weights. It didn't register at the time and got binned. It now has an MGB one.

I've come to the conclusion that the distributor / cam was from something else as max torque seems to be around 3,500/ 3,700 rpm .

I suspect that the cam is a slightly de-tuned one from something like a Riley/Wolseley saloon with slightly more mid-range.

Any ideas?

Mart

Reply to
Mart
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Perhaps the whole motor was from the Austin Marina. Dreadful device, used by British Leyland to wreak revenge on colonials who refused to buy their other products in the 70s! I think in the UK they got smaller motors but here in Canada they came with an anaemic version of the 'B' engine.

I've never much liked Weber sidedrafts for street use, so when the SUs got tired beyond help, I chucked 'em over a hedge and replaced them with a pair of Mikuni HSR 42 flat-slide bike carbs, and they work like a dream. At

42mm they're just about half way in size between the stock 1 1/2" SUs and the 1 3/4" used on some competition Bs back in the day. Like all Mikunis they are very well made, reasonably priced, and jets etc. are readily available.

The HSR series are used a lot on hotrod Harleys, but don't hold that against them. They mount easily to a stock MGB twin carb intake manifold, using spigots and rubber sleeves. Since they are intended for gravity feed fuel supply, even the low pressure pump in the B blows the needles off their seats so I had to put a fuel pressure regulator in the line and reduce the float levels to stop them pissing fuel on the ground.

The carbs have pumper jets, so throttle response is excellent from all settings. They also have plunger type chokes, which meant rigging a two-into one cable pull via an old Norton throttle cable splitter box. Easy, cheap and quick to rig. The carbs, including a pair of foam filters and a handful of jetting needed to dial them in, cost me less than a new set of HS4s and they are twice the carbs. Adjustments are gradual and predictable and involve no mystical incantations or offerings to the gods of Skinners Union. It doesn't matter which side of your mouth you hold your tongue in when synchronizing them, and they steadfastly refuse to leak either air or fuel.

My car is a ' 70 B-GT with a fresh engine, .040" o/s pistons, the 'competition' cam described in the BL Special Tuning handbook under 'Stage

Reply to
Kevin Hall

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