Just bought a 1964 Mg midget!

[youngcamper]

Right all,

I've just done the compression test and these are the results ( working from the front the car back)

Cylinder 1 : 180
Cylinder 2 : 180
Cylinder 3: 180
Cylinder 4 : 90

What does this suggest ? ( btw she is burning no oil )

I am now thinking a burnt out valve or possibly the gasket.

[MarkyB]

Cylinder 4 : 90

Clean up in aisle 4!

Something is amiss there, could be a valve, my money, all 2p of it, is still on the head gasket.
I'll put £1 on the head needing to come off though.

[youngcamper]

The head will be coming of shortly !

Then we'll know whats what. I'm hoping its the gasket but I believe that it's unusual for it to go on cylinder 4, doesn't it normally go on 2 or 3 ?

[MarkyB]

Unusual doesn't mean it never happens!
It's like Roy saying it's never the coil, he means it's unusual, really.
How boring would life be if everything was predictable?

[youngcamper]

Ahh I see.

Lets hope so .

[bmcecosse]

Hmmm - the fact you said earlier that it ran 'ok' again after cooling down could mean that the valve gaps had closed up - and then opened slightly when it cooled. During that time - the valves and/or seats could have been damaged - so it could be a valve/seat problem since the other 3 values are actually very good. Off with it's head and let's see.......

[youngcamper]

Right the heads off and the gasket seemed to be in good condition. so that means no distortion of the head or block . The valves on No. 4 look like they need re-grinding ( is that what its called ? ) so Dad will be helping me with that tonight or tomorrow.

Anyone who claims to change a gasket in a lunch hour I take my hat off to you I'm about 1 and a half hours in and its still all in bits !

[charlie_morris_minor]

Unless you check that the head / block are true you can say with certainty that they are not distorted.

by the way glad to see the problems are not putting you off suggesting buying a midget to other people on the board

[youngcamper]

too be fair this problem could've occoured with any car I'd bought. I'm just glad its got the same engine as my moggy. That way I have some idea what I'm doing .

The marks left on the head by the gasket ( the little rings ) look pretty uniform, where as the valves look a bit crusty, I am pretty sure that these are the problem.

[MarkyB]

Unless you check that the head / block are true you can say with certainty that they are not distorted.

You might as well say that unless you get it crack tested you can't say for sure it isn't cracked.
I would say the fact that the head gasket is OK, even after some over heating is a good test in itself.

[youngcamper]

Well interestingly it turns out its got a 12G206 head, I've never heard of one of them before. Comparing it with a 12G202 shows that it's basically a ported version with slightly bigger combustion chambers and double sprung rockers but the same size valves.

Anyway The valve has been re seated but to be honest it wasn't really that bad. I think while I'm at it I'll change the valve guides as there is a little play.

[bmcecosse]

Yes - the 206 head was fitted to Spridget engines, it won't have location rings for the manifold, but it should have the larger 1.25" inlet valves. Measure them carefully! The valves will have double springs - not the rockers.

[youngcamper]

that sounds about right BMC. It does have smaller valves than a 12G295 head though. Sorry I meant valves not rockers.

[bmcecosse]

That's interesting - because they SHOULD be the larger inlet valves. However - the 1.25" valves are not easy to get hold of, and someone may have fitted the smaller normal 1098 inlets which will 'just' seat down on the head even though it is intended for the slightly larger valves. This should actually give better flow!

[youngcamper]

I will be giving them a measure tonight. I have treated the head to a new set of valve guides as the old ones are rather worn. I am still not convinced that it was a burnt vavle but I guess I will never know for sure.

Cheers,

Will

[bmcecosse]

Well - if in doubt, pop the pistons up and have a look at the rings......

[youngcamper]

I've put some oil in all 4 bores and will check for leakage tomorrow. I have also fitted new valve guides and seated the valves. I've also got a new Dizzy cap and HT leads to fit. All being well she should be running tomorrow.

[youngcamper]

Well she's back on the road and running brilliantly .

Thanks All

[bmcecosse]

Great success. But do now retorque the head and then reset the valve gaps.

[youngcamper]

Already done . Thanks BMC couldn't of done it without you .