Midget 1275 woes

[akuchanny]

Hi all,

I pulled the head on the midget engine in my morris today thinking as three cylinders where showing bad compression that I had bad valves in the head, only to find two sets of parraell score marks on the front of cylinder 1 and the back of cylinder 4. 2 or 3 mm deep! I have called around and the consensus seems to be gudgeon pins coming loose in the two cylinders. I think the block might be scrap now or will need liners, the only problem was I was originally planning to supercharge the car and am no worried this block (if salvaged) will be too weak.

Has anyone any ideas if this block will be too delicate now, and how on earth two sets of gudgeon pins worked loose!

I'm now on the hunt for a 1275 standard bore midget block if anyone knows if there is one.

Thanks in advance

Andy

[philthehill]

Andy
I am very sorry to hear of your predicament.
The 1275cc Midget/Sprite engine gudgen pins are a very tight press fit in the small end of the connecting rods and something serious would have to have happened for a gudgen pin to move. Therefore I doubt that the gudgen pins have moved in the small end of the connecting rod.
With the 998cc 'A' series engine fitted with fully floating gudgen pins it was a common occurrence to loose a circlips and the gudgen pin would then move sideways and score the bore. That is why the 998cc 'A' plus engine resorted to press fit gudgen pins
I suspect that you have got broken rings (which is a more plausible reason) but you will need to draw the pistons to confirm the problem.
I would not give up on the block but draw all four pistons and give the bores a full and comprehensive examination before deciding what to do.
I personally do not see or would have any problem with fitting liners and still supercharging the engine. The extra supercharging pressure is not that excessive.
A good quality photo of the damage would be appreciated.

These are the dimensions that you need to know if the bores are not sufficiently damaged to preclude fitting liners.

Cylinder liners:-
Outside diameter..............2.8775" to 2.87825" (73.09mm to 73.106mm).
Interference fit in cylinder block..............0.002" to 0.00325" (0.05mm to 0.08mm).
Bore of cylinder block - machined before fitting liner......2.8750" to 2.8755" (73.02mm to 73.04mm)
Bore of cylinder - machined after fitting (standard)....2.779" to 2.7805" (70.59mm to 70.62mm).
The above taken from BL workshop manual relating to 1275cc in line engines.

I would suggest that if you can get under the scoring at 2.8" diameter it is and would be perfectly feasible to fit liners to your 1275cc block without detriment to any future supercharging ambitions.
Phil

[akuchanny]

Thanks phil,

I will try to get some in the light, am pulling out the 1310 i have in bits and taking that with my cylinder head to a engineering firm, hopefully that will end up with a bullet proof engine...fingers crossed..

To keep the car going, as it was still running i am going to put another head back on the block and run it for a few weeks. Not idea but between the devil and a hard place.

Hoping to get the original 1275 sorted next year and i can build it myself, unless i kill it, which i really hope I don't.

Unless this is a foolish idea?

A.

[philthehill]

There is no such thing as a foolish idea.
Personally I would get hold of a running 1098cc and put that in for the interim so as not to make the problem with the 1275cc Midget engine any worse.
Phil