MG "B" Series Engines and Oils

[bunnspecial]

Just to follow up, cleaning the ignition points solved my backfire/misfire problem. A new set of points is in my future(probably on my next order from Moss, which tends to be roughly every other week) but for the time being it's fine. This is the second time while in my ownership that the points have been filed(the first was in a gas station parking lot about 30 minutes after I'd bought the car

) so I think I'm buying time on them.

It looks like I get to invest in a dwell meter also.

 

[BrocLuno]

Your points are pitting and sticking because your condenser (capacitor) is going bad. Go get one spec'd for a FORD V8 from the 1960's and it will help save your points.

 

[riggaz]

According to the MGB workshop manual you should have between 10-25psi on idle and between 50-80psi during operation

Depending on ambient temp the recommended viscosities are 5w-20, 5w-30, 10w-40, 10w50 and 20w-50.

above -10'C 10w-40, 10w-50 or 20w-50 are recommended.

Unless you're somewhere very cold or very hot I'd be using a 15w-40 mineral oil personally.

 

[CATERHAM]

Thanks for digging up to oil pressure spec's although 80 psi seems higher than what I would have thought the oil pump relief valve setting would allow for a 'B' engine. Of course that's easy enough for the OP to check by simply raising the engine rpm on a cold engine to see if 80 psi can be reached.

Fortunately compared to some other parts of the world motor oil is relatively cheap here in North America where premium synthetics like 0W-40 and 5W-40 can be had for as little as 5 bucks a quart/litre. So unless you've got a serious oil burner, there is no reason to use antiquated low VI 15W-40 and 20W-50 grades.

 

[Gokhan]

Originally Posted By: CATERHAM
Fortunately compared to some other parts of the world motor oil is relatively cheap here in North America where premium synthetics like 0W-40 and 5W-40 can be had for as little as 5 bucks a quart/litre. So unless you've got a serious oil burner, there is no reason to use antiquated low VI 15W-40 and 20W-50 grades.

Agreed with this recommendation. Go with M1 0W-40 SN if oil consumption is not a major issue. If oil consumption is too much, feed it with 15W-40 or 20W-50 not just to reduce the oil consumption but even more importantly to reduce the hole in your wallet.

10W-30 is probably too thin given the mileage of your engine, which would increase the oil consumption. Also, xW-40 is right in the middle of the OEM-recommended grades.

 

[pdxglocker9mm]

Originally Posted By: expat
Going to an electronic ignition can make a huge differance in overall performance. But, to be honest, I do not have much faith in optical ignitions such as Crane.

In the past I have used Allison kits and Piranha only to have them fail, and when they do, they die in an instant!

No manufacturer (that I know of) ever used an optical system as OE

Ultimatly a crank triggered system like Mega Jolt is the way to go. But anything is an improvment over the standard Lucas points distributor.

Unless it's a Lucas electronic distributor

General Motors did infact use optical ignition timing as OE
It had its own issues. It looked very cool on paper and with some further engineering it might have worked.
Optispark!! It knew with in one degree where the crank was.
But the issues were mostly related to moisture intrusion due to poor sealing and location

 

[riggaz]

Cold engine oil pressure will tell you nothing about whether you are running the appropriate viscosity oil, the oil pressure readings are for engines at operating temp. It gives a 40psi to 80psi range so that, when running between 2000-6000 rpm (or whatever they rev to), if your engine is straying outside of this range then there may be a problem either with the engine or with the oil you're running.

Engine clearances are designed with the available oil at the time in mind (including the oil pump). We've had it in one historic engine in which the customer wanted to use 0w-40 Mobil 1 and the oil was draining out of the oil pump overnight and making the engine knock on start up, put 15w-40 mineral oil in and it was ok again (just).

A well additised mineral oil will, in all but the most extreme temperature or drain interval conditions, give comparable wear protection to a synthetic oil. The best thing to do with older engines is choose a well additised oil and match the viscosity to the engine design.

The only reason there would be to run Mobil 1 0w-40 in a BMC B Series engine would be for cold pump performance in less than -10'C ambient temps, and marketing hype of course

 

[artificialist]

Originally Posted By: pdxglocker9mm
Originally Posted By: expat
Going to an electronic ignition can make a huge differance in overall performance. But, to be honest, I do not have much faith in optical ignitions such as Crane.

In the past I have used Allison kits and Piranha only to have them fail, and when they do, they die in an instant!

No manufacturer (that I know of) ever used an optical system as OE

Ultimatly a crank triggered system like Mega Jolt is the way to go. But anything is an improvment over the standard Lucas points distributor.

Unless it's a Lucas electronic distributor

General Motors did infact use optical ignition timing as OE
It had its own issues. It looked very cool on paper and with some further engineering it might have worked.
Optispark!! It knew with in one degree where the crank was.
But the issues were mostly related to moisture intrusion due to poor sealing and location

Nissan used basically the same thing on the 1982 280ZX and almost every computerized distributor after that.