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MG Midget and Sprite Technical - Name that head

Following on from what was originally a breather setup issue, can anyone confirm what the cylinder head is in the attached photos from my recently purchased Sprite? The block has no push rod access plates so that means it is a 1275, right?

I removed the rocker cover and found the following numbers:
12G940 909 15A

All help appreciated
Ant


Ant Allen

Another photo


Ant Allen

Last photo


Ant Allen

Ant,

i don't have any referance books to hand, but i believe a 12G940 is a standard 1275 midget head.
Brad
B Richards

it is

12G940 is the most common 1275 head
Onno Könemann

Ant, it is a standard 1275 head, and this can be confirmed by looking at the position of the heater tap screw threads, in your case diagonal. on the 1098 they ae straight across the head I believe

Someone mentions this as an identifier on the "breather thread"

Many people have "issues" with breathers on these engines because of leaks, since the earlier style rocker cover you have is venting to air somewhere near the N/S front end I reckon somebody thought this would solve his leak

it wouldnt though IMO

The A series needs the internal suction effect of breathing into the manifold to control the leaks

The crankshaft doesnt have a seal, as such, but has a close fitting reverse spiral groove in the back of the crank that (sort of!) controls any tendency to lose oil through the back of the crank. It needs the lower internal pressure to hold back leaks

It can work well-ish

It rarely works well.
Bill

the most remarkable thing about that engine is that the engine number tag is still in place.
Mike Allen

"the engine number tag is still in place."

and still rivetted too

Bill

It looks to me like an early 1275 engine, the colour and rocker cover show that, the early rockers are also interesting as they look very much like Cooper S ones....

Mark.
Mark T. Boldry

Looks exactly like the engine in my Mk3 Midget, built Dec '70
Margaret Brock

Thanks to everyone who has helped thus far. I'm extremely relieved that it's a 1275 head!

So, if the head and block are a matching pair and are "an early 1275", what breather system should I have? It seems to me that a breather control valve should be fitted to the pipe which is currently blocked off on the inlet manifold (rather than the Y connection into the carbs for which there's no pipe on the carbs themselves on my car). If so, could it be that early 1275's had a rocker cover outlet going to the breather control valve rather than a timing cover outlet?

Full engine no is "12CE-DA-H 186" and chassis no is "A-AN10 1 - 86868".

Ant

Ant Allen

Margaret - crossed posts! If you've got one like mine, does it have a rocker cover breather outlet? If so, where does it connect to?

Thanks
Ant Allen

A -AN10 is an Austin Sprite (no Healey)
They started at 86803 so yours is an early one, built about Jan, maybe early Feb 1971

The 12CE DA-H could be anything from '67 to 71. Maybe the correct engine that has "aquired" a rocker cover from an earlier car?

Guy
Guy Weller

Guy, I think your theory is close to the truth.

Mark.
Mark T. Boldry

Ah, but does it have a "can" on the timing chain cover?

And the chassis plate is in the wrong place.
Guy Weller

Completely pukka 1275 motor from an Austin Sprite, very early '71.
As Guy surmises - looks like it's just got an unoriginal rocker cover.

As original, it would have had an unvented (apart from the filler cap) rocker cover, with the mesh filled canister on the timing chain cover, connected by hose via a Y-piece, to vacuum stubs on each of the SUs.
Steve Clark

Ant, I'll have a look tomorrow and post a photo
Margaret Brock

The rockers are the forged Cooper S type, as fitted to early Midget/Sprite 12CC engines, not 12CE AFAIK, and certainly not in 1971.

Dave O'Neill 2

OK,
How about this then: The engine (block) is correct for the car. i.e. early 1971 in an Austin Sprite.
And at some stage a PO has fitted an earlier head off a 1275 car, (or even of a Cooper S!). That would fit with the breather on the rocker cover and the different rockers. But the presence or otherwise of a can on the timing cover would clarify.
I am puzzled by the position of the VIN plate - it should be on the sloping inner wing rail beneath the carbs.

Of course a Heritage certificate would give the original matched engine and chassis numbers and the day of manufacture. But they are quite expensive now - up to £40 I think!

Guy
Guy Weller

Checking numbers.
My chassis number is only 140 engines after yours. It was built 5 March 1971. But the engine number on mine is 12CE-DA-H 15thousand and something. If yours is really just 186 it makes it an early '67 engine, and not the original engine for your '71car. But still a 1275, so that's OK then!

Guy
Guy Weller

12G940 is the most common 1275 head


Yeah Right,,,they come up vary rare over here...I think someone is hording them all on this side of the pond, the most common 1275 head here is the 12G1316, its a copy of the 12G940 but has the smog holes and a thicker bolt down area as a result

prop
Prop

It's not a Copper S head, thats an AEG163, like the one on my engine :-)

Brad
B Richards

I've very grateful for all the help so far. We appear to be gradually sloving the mystery of the breather setup.

At the moment we've found the following confirmed:

- 1275 Block, no tappet chest covers, consistent with 1970 production.
- 1275 head, circa 1970, with cast (early) rockers.
- Manifold and carbs match each other with the breather connection on the manifold.

So the outstanding oddities are these:

1) The rocker cover has a breather outlet spout on it, as per 1098 engines.
2) The timing cover doesn't have abreather outlet, again as per 1098 engines.

Were any 1275 engines ever made with the breather coming from the rocker cover? Has anyone got one?

Ant
Ant Allen

Ant,
I think that engine number indicates an early 1275, from 1967. Maybe the very early versions still used the 1098 breather arrangement?
Car itself is 1971. Probably February. Could be a Valentines Day car!

Guy
Guy Weller

Photo as promised (hopefully!)


Margaret Brock

And another


Margaret Brock

And finally


Margaret Brock

Margaret,

Thanks for the photos. Yours is a later 1275 with the Y piece into the carbs. I haven't got that capability. What is nice to see though is that the inlet manifold port still exists on yours, but is blocked with a plug, whereas mine has a short hose and a po attempt at blocking it off - suggesting that mine shouldn't really be blocked off at all.

All - I'm still puzzled as to whether the very early 1275's might just have had a rocker breather vent and no timing cover vent. This is what I have. Why on earth would someone swap the rocker cover and timing cover from a 1098 onto it???

Ant
Ant Allen

Mine originally (when I got it 21 years ago) had a 3 branch exhaust manifold, and only a short heat shield, which didn't exactly do anything! So when the manifold develloped a crack, my garage changd it for the present one, and the correct heat shield. But I lost power, and have since been toying with the idea of reverting back to the 3 branch manifold. Next week she will be put through her paces once again, as we have our annual Scottish holiday coming up. Keep your fingers crossed for good weather in the Blair Athol area!!
Margaret Brock

Parts car.
There is quite a lot of overlap on parts when they brought out new models , whilst they used up what was left in the parts bin from the previous specification. Perhaps this applied to engines too!
Guy Weller

Hi,
according to the Original Sprite and Midget book it states that with regards to the 1275 engine:

'Ventilation was initially by closed circuit recirculator valve fitted to the inlet manifold, but, without the removable valve chest covers, the crankcase outlet was now located on the front of the timing cover casing'

it doesnt look as though not having a cannister onb the timing cover was ever an option, my car is a Sept 68 and I have the cannister.

Moss lists the rocker cover with outlet as all 948cc and 1098cc engines.

HTH
Mark
Mark Whitmore

I got to agree with onnno and B richard

its a 12G940


BUT!!!!

According to vic brit the engine is a 67-69 sprite

Im guessing its a hodge podge, one piece at a time throw togather engine. Id be curious as to whats inside, obviously they where using solid parts to build it

ribbed block, 12g940 head, cooper forged rockers, vented valve cover, vacume "Y" ported Su carbs....you know there got to be some nice toys inside...to solid for accidental put togather

prop
Prop

So, moving forwards, looks like I need a timing cover with a vent, a rocker cover without a vent, and a diaphram breather valve for my inlet manifold. The first two are out of stock at Moss and MGOC. Any suggestions?

Ant
Ant Allen

Ant,
If you look for a timing cover with vent off a mini, you will at the same time get your timing marks into the daylight where they can be seen!

But apart from that, why not just accept it as it is, that set-up worked well enough on the 1098 engines.

Guy
Guy Weller

At the moment the rocker breather just goes to the floor, and I have unacceptable oil leaks. I want to get the breather system working properly to drop the crank pressure below ambient. Only then will I know whether the leaks are a problem in their own right or not.
Ant Allen

here's a rocker cover or two !
http://tinyurl.com/6xxwxf
David Smith

Ant,
What I was meaning is that changing the timing chain cover is quite a hassle with the engine in the car. Why not connect the rocker cover to the manifold via a PCU. It all evacuates pressure from the same internal spaces in the engine. In fact, as a short-term test you could connect direct to the manifold without a PCU although it may "suck" too much. But worth it as a test.

Guy
Guy Weller

Guy - I see. Yes, I can certainly do this to see if it solves my oil leaks. I believe the intention of the timing cover outlet is that a small amount of air enter via the oil filler cap breather hole and travels through the engine to "flush out" stale blowby gases. I'm much less sure about this theory though.

How hard is it to get the timing cover off with the engine in the vehicle?

Ant
Ant Allen

you have to free off a few things until you can jack the engine under the sump so the bottom pulley will clear the crossmember...
David Smith

Ant,
To remove the timing cover you need to remove the crank pulley. Which means removing the radiator to gain access. Then undoing the crank pulley bolt can be a bit of a bear, - they are usually exceedingly tight so you need all the access you can get. To get the pulley off you also need to jack the front of the engine up so it clears the front cross member, which of course means undoing the engine mounts and possibly also the exhaust to manifold connection. It is almost easier to take the engine out.

The proper 1275 venting system allows a small amount of air to enter through the oil filler cap and it builds up a crankcase vacuum - or at least a little below ambient pressure. I presume that the connection from the rocker cover would do much the same but I am not sure where it draws air in. I suspect that it might pick up more oil splash from a rocker cover connection, but the system worked well enough for years.
Guy Weller

I would not recommend venting directly to the manifold as it will be a huge vaccuum and make tuning near impossible. Not an expert or anything, but my 72 had a similar breather on the rocker cover before I replaced it. I believe it was the fresh air intake for the crankcase made to be used with the non-vented cap, and was connected to the canister filter. Of course I cannot verify that mine was original:) CJ
CJCharvet

I did this recently and everything Guy said + exhaust off, and had to pull the engine forward a bit to allow the gearbox to clear underneath the heaterbox part of the tunnel so it would jack high enough.

Also needed starter motor out to allow a jambing bracket in the starter gear teeth to stop engine rotating when undoing the pulley nut.

Richard.
richard boobier

Ant

I have all the parts you need.

I have had to remove the timing cover with the engine in the car on several occasions. For some reason, the oil seal would sometimes fall out when fitting the bottom pulley and I only discovered this upon starting the engine and finding a huge oil slick under the car.

midgetbitz (at) gmail (dot) com
Dave O'Neill 2

I think the head should be called Valerie. Will wait for the postman to delivery the Blue Peter badge.


Alex Sturgeon

This thread was discussed between 19/10/2008 and 21/10/2008

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