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MG Midget and Sprite Technical - Thoughts on this head - reskim or???

Hi
Following on from an earlier post - I have removed the valves from 3 and 4 and cleaned up a bit but there does seam to be some pitting around three/two and 3 exhaust is well cocked up. Skim or ??
TIA
Dave




D Price

A closer view between three on the RHS and two
Dave

D Price

Dave,
I had the head skimmed last year and 5 valves resurfaced at reasonable cost. I was concerned as I'd already had the head skimmed before and had no idea if it'd also just been done before I got the car as it was a recon engine with 50 miles on it. The chap doing the work said not to worry as there's plenty of meat on A-series heads. I don't think the small changes to compression make much odds on our engines (I certainly haven't noticed at any point).
Nigel Atkins

The very narrow neck between 2 and 3 on a 1275 engine is prone to leaking. Its difficult to tell from that photo but I think I would get that resurfaced, just a light skim.

Alternatively you might want take the opportunity of an intentional increase in CR in which case do some research and careful measurement of the combustion chambers to work out how much to take off. Mine has a 10.5:1 CR which works well with my engine spec, and I wouldn't want to go any higher with normally available petrol.
GuyW

Pitting means there has been water in the cylinder and corrosion, but this can happen by itself over time if an engine isn't run regularly and won't usually cause any significant issues.

Valve seats might be suspect and should be checked/relapped. Build up of crud on stem can be cleaned off with a wire sheel, could be indicative of a worn valve guide or piston ring, but again, if the engine isn't smoking then not a big deal - decokes used to be part of regular servicing.

However, is this the same head as the suspected HGF? In which case you should identify the cause of that before doing any work.

I've had a similar failure as Dave B, in my case a crack in the top face of exhaust port and thus steam from tailpipe and eventually overheating. This could cause your symptoms of water in cylinder if the engine was stopped with ex. valve on #3 open.
AdrianR

Hi Please see attached. It looks as if the gasket might have gone. I would be surprised if it had cracked in a two mile run as no evidence before but ???? The first symptom was trying to start the car at the garage - very slow tickover and lots of smoke. First thoughts was I had put diesel in!!! When running back to house - 2 miles no issues at speed but at tickover - cloudy!! When I did a comp check - all plugs out - water spat out of 3 cylinder spark plug hence thinking it was that. I had done a comp check about 2 months ago post tappets etc- was getting 140 across the board - standard 1275 engine.
TIA
Dave
D Price

Dave,

Not sure where you are in Devon but years ago there was a machine shop in Haven Road, Exeter down by the canal - used them a lot - seems there still is but I don't know if its the same company.

I understand another in Tivi but don't know them.

If you have doubts a light skim will be a good idea.

R.
richard b

Yep, looks possible that there is a breach between cylinder bore and water passage there. You can do a basic check for flatness with a good steel rule and shining a torch behind it, or some feeler gauges. Check both head and block between cylinders and across the suspect area.

In my case I think the crack was a secondary effect - car had lost some water due to a split in the thermostat bypass hose but like you, I decided at the time that it was OK to drive home to fix.
AdrianR

This thread was discussed between 02/08/2021 and 04/08/2021

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