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MG Midget and Sprite Technical - valves

Hi,
I have removed the head of the engine (948CC).
The inlet valve from the first cylender (near water pump) is light brown.
All the others are black (calamine?).

What does it mean?
laurent
ld derancourt

The brown one has been hotter than the others. Most likely it had less contact with the valveseat. Was the valve clearance less? Is the valve head burned. Is the distribution of the brown color even? Do you have a photo?

Flip
Flip Brühl 948 frog 59

hum.... in fact it is the exhaust valve near the gearbox.
I have to stop to drink wiskhy.......

one photo below.


ld derancourt

Hiya

Why did you remove the head?

Is the engine burning much oil?

Peter
peter burgess

Oh I have to give some explanations:

Running midget GAN1 (the white one)
the engine burns oil (lot of smoke)
the engine leaks
the clutch is slipping (plate with a lot of oil)
spigot bearing destroyed
the head is a unleaded 12G202 (4000 km)
948 + 0,04"piston

Project Ashley Midget GAN1(the blue/white)
The engine starts first time
no smoke
waterpump failure
head is certainly not unleaded
948 piston

As the engine of the running midget has to much troubles, I decided to restore the main engine with the project chassis.
And I decided to make an engine for the running midget, taking the main engine in good order from the project car and to put on it the waterpump and the head of the leaky engine.

One more thing: the head of the project midget has got a lot of black scale on each valves. But no sign of overheating with a light brown colour.

So I wanted to know if it was possible to fit the head with a brown valve on the block, or if this head has to be machine?

I have a third head 12G202 with big valves in new condition. But I am not sure those valves (33 and 29mm) will fit the 948cc block. I wanted to use it for the Ashley with an engine rebored to 998 + 0,04".

laurent



ld derancourt

the Ashley


ld derancourt

The valves look good. Cylinder 4 burns leaner than no 3 (look also at the spark plug) which is normal with an A motor. Overall it looks like you can make the mixture leaner os stop the oil leak. There is a lot of coal. The color of no 4 is normal no 3 has too much coal (blue smoke) How where the cylinders, and the piston rings?

Flip
Flip Brühl 948 frog 59

I wonder if this is the result of the heater vavle tap being closed and not allowing the water to flow thur the back part of the head.

Im baseing this on the 1275, but i assume its the same basic engine configuration just smaller, with a few differances here and there.

Prop
Prop***The End in 2012

Hiya

The valves that are black in the first head you mentioned look like oil contamination to me. If the carbon deposits are oily( wipe your finger over the chambers and see if your finger comes away black and oily not just dry soot black) then the problem is from a worn out engine, with 4 still running somewhere near ok. Strip the head and inspect the valves and seats for wear. A series are little so-and-sos for eating exhaust valves when oil is being burnt. Ensure you reassemble with top hat style seals on the inlets at least.

The 1275 size valved head needs cutouts on the block to ensure the valves cannot strike the block.

Peter
peter burgess

Piston rings have been change but certainly badly done by the mechanics. Cause after this change, I had an important smoke. He said it is normal, piston rings have to find their place. But 4000 km after, it is still smoking!!!!!

the sides of every cylinders have got oil on the complete surface.

This block need some work before using it again.
So I will do one complete engine with the two.

many thanks
laurent
ld derancourt

Im guessing they didnt use a break in oil for seating the new piston rings the 1st 500 miles and the cly. glazed over
Prop***The End in 2012

they just fitted new rings and left the bores intact when it should have been over bored and honed

Onno Könemann

Good point Onno, that to!!!

Prop
Prop***The End in 2012

This thread was discussed between 26/03/2009 and 28/03/2009

MG Midget and Sprite Technical index

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