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 Midget and Sprite Technical - 1275 Manifold & engine rebuilding

After a pleasant trip out last Wednesday, the last 5 miles ended in frustration with a bad misfire.
Pulling plug leads at home leads me to suspect the head gasket has gone between 2 & 3 again. Somewhere in the archives is another post from me from about 500 miles ago (10 years to my shame) with the same issue.

Anyway I have started stripping it down with a view to a short term fix of another head gasket, just to get me to a couple of local events next month.
Removed the manifolds and a big chunk of metal fell off the exhaust manifold (pic attached), one of the mounting lugs. Looking closely at the break it's rusty inside and would appear to have been welded at somepoint in the dim and distant past.

On searching the archives, it would appear that there is no fix for this, so does anyone have a spare 1275 bell clamp type manifold they would be willing to part with?

Regarding the head gasket, from the general state of the engine last time I looked a rebuild is on the cards and this time round I might be able to afford it.
Block will need a skim, pistons are marked +.030, and at least one will need replacing, even if a rebore is not required.
Does anyone have any recommendations for someone/where who could do this work in the North Wiltshire area?
I have no experience of rebuilding an engine, I've never even removed the midget one ... yet.

Cheers




G Hawkins

I can't help with the manifold, but have you done a compression test to see what state your engine is in?

Did you retorque the head last time?
Dave O'Neill 2

I've not done a compression test this time, I suppose I still could if I can locate my tester, the head is still on. My wife tore the ligaments in her ankle Thursday so garage has been out of bounds since then. Got the call to collect her from work just as the exhaust manifold revealed it's issues.

Did I retorque the head?
I remember searching the archives and coming up with so many conflicting opinions (yes/no, hot/cold, to loosen first or not, 1000 miles, 500 miles, after it's reached running temp etc...) I was more confused than ever. So I went with what I successfully did on my Mini engine back in the day … nothing.
G Hawkins

Hi Grahame
Get well soon, Zoe!
I’m out of the country till Thursday but after that I will call over with a compression tester if the head is still on, and we can remove it together if you like. I have a tubular manifold you can have.
Give me a call!
Andy
A Cross

Cheers Andy.
G Hawkins

Further to this got the head off this morning. Nicely burnt gasket between 2&3 as suspected.
I did find my compression tester before removal and got 175:0:0:175

Anyway a new question which I cannot find in the archives.

On the block top surface by each of the 4 longer studs (towards the outer edge) there is stamped a number 2 inside a diamond (square rotated 45 degrees)

It may be common knowledge but what does this mean/indicate? Can't imagine how I've never seen it before although I am using my nice new 4ft LED batten inspection lamp.

Pic attached.



G Hawkins

That indicates the size of the bore, with regard to machining tolerance.

When the engines were machined at the factory, the bores would have been measured and the block stamped with a number to indicate the tolerance. The engine assembler would then select a set of pistons of the correct size.
Dave O'Neill 2

Unusual to get a zero reading in a conventional compression test, even with a blown head gasket.
GuyW

Dave, thanks for the info.

Guy, Maybe my Frankenstein tester (bits of 2 cobbled together) is less than accurate especially at low pressures?

Stuff is going back together slowly, progress interrupted by a knackered water pump, whose outlet (inlet?) was far to corroded to fit a new hose to.
G Hawkins

Hi G, I think I have a manifold, will look later.
Clive Berry

Well got the car back together and running 2 days ago.

Had issues with the tubular manifold from Andy in that the centre branch hit the heatshield, not uncommon my research tells me. Tried to bend my heatshield up a little to clear and it just started cracking so reverted to Plan C (still got 23 plans to go!) which involved bodging the old cast iron manifold together again. Given the weld that had been done before my ownership lasted best part of 30 years I figured I could get it to last another summer...maybe.
MIG welded it on full power whilst heating the flange with a flame, and left the flame on after welding for a bit then left to cool. Cleaned it up and bolted it on with no issues.

Water pump needed swapping as on removing the hose to swap for a new one (hose end was splitting) it took lots of the alloy pump with it and left behind a mishapen lump.
Another trip to Somerford Minis and a nice new pump sans bypass hose as I'm using a Metro head and had blocked the previous pump outlet.

Carbs back on and guess what, the choke cable is too frayed to get back through the hole in the linkage ... pull the inner out and weld the end up and clean it up, but will it thread back into the outer ... of course not.
Right I think I have an old cable from something else in a crate of spares and after a suprisingly short search I find it and fit it. Another spanner has given it's life in creating one just for undoing that choke cable nut behind the dash.

Anyway long story still quite long it started up, ran up to temp. No leaks, no strange noises. Left to cool overnight and nuts retorqued and valve clearances rechecked.
Just been for a short run (6 miles ish) to get petrol for the mower and it ran fine, so we'll see how long it lasts this time. Long enough to get to a local show tomorrow with luck.

Meanwhile I will continue to look for someone to refurb this engine at the end of the summer (if it lasts that long) or consider getting a recon unit from somewhere.
G Hawkins

This thread was discussed between 19/05/2019 and 01/06/2019

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.