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Midget Head Gasket failure


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As some will have seen on the Malvern photo's thread, the Midget had to be recovered from just East of Tewksbury to home in West Sussex- it took the RAC 26.5 hours and three separate transport truck, but that's another story!

The head is now off and the gasket has been completely burnt away between cylinders 1 and 2 - creating a 3-4mm gap in the gasket. Some of the copper from the gasket appears to have 'welded' itself to the cylinder head - I need to have a better look at the block to see if something similar has happened there.

Has anyone any thoughts or advice on how best to clean the head (and the block) surface and to get this copper off without scratching/damaging the head (and block).

Thanks

Rod

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TBH I would definitely get the head lightly skimmed to start, The block would probably need to be done with a large dead square rubbing down block and some 320 W/dry with some oil for lube, you would need to plug all the bores/oil ways/waterways to prevent any ingestion of the removed lube..

Stuart.

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Thanks for the reply Stuart.

I took the head around to a friend who has a good flat plate and dial gauge set up and we determined that the head itself, having only done circa 7k miles since a full engine rebuild ~11 years ago that included a skim, is flat, and the issue is/was a raised section of deposited copper ~3mm wide and about 1.5 thou high between cylinders 1 and 2.

I then went to our local garage where one of the mechanics has rebuilt sprites, midgets and MGB's over the years. Looking at the head his advice was to very carefully use fine emery, lubricated with duck oil/wd40, to remove that raised section. I have done that today and all looks pretty good. I now need to do the same on the block which has a similar deposit of copper.

I need to get a really good straight edge to check the block - I have a long spirit level which I think would do it, but if I can find something better I will. Then it is refitting.

I have a few more questions if anyone can help:

How clean does the head and block need to be? I've used Carb cleaner to remove a lot of carbon deposit but there are still dark areas - presumably it doesn't need to be spotless as much of the deposit is within the still visible machining marks on the head.

I have sourced a couple (in case I mess up one) of copper (both sides) head gaskets but they don't have 'Front' or 'Top' marked on them. On one side the steel sealing rings for the combustion chambers are visible - would I be right to think tat this would be the upper/top/head side?

One last question - should I use any additional gasket sealant, or fit dry? If a sealant, what would be the recommendation?

Rod

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My view FWIW, is the same as Stuart’s. It costs what? £50 or £60 to get the head skimmed a couple of thou and then you know it’s good. 

The block needs to be flattened as best you can. 

I always fit head gaskets with the fire rings facing the block but I’m sure someone will come along with the definitive answer. 

Rgds Ian

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Forget about using a spirit level or other edge unless a steel rule that stretches the block. Use ground silver steel which is made to very close tolerances 

T & A Precision Silver Steel 1/2" Diameter X 39" S| at Zoro Steels

This one off e bay offers 39" length 1/2" ground silver steel at £11 per length. It will be within a thou along it's length and useful to use with feeler gauges to pick up any warp along the block length.

Mick Richards

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14 minutes ago, Rod1883 said:

Thanks Ian, Mick

Mick - do you have a link as I can't seem to find the item you refer to on Ebay

Rod

Here you go Rod https://www.cromwell.co.uk/shop/materials-and-maintenance/silver-steel/1-2inch-dia-x-39inch-silver-steel/p/CTL4325054X

Stuart.

Edited by stuart
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I suppose it's a Midget with the Spitfire 1500 engine, ie with recessed bores, not an older BL version, with the flat bores engine ?

 

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Thanks Stuart, ordered.

Chris - it's a very early 948cc A series engined car.

I've sorted out which side up the HG goes. As I posted above I thought the gasket was copper both sides - the reason being it comes in a nice sealed, fairly thick orange transparent plastic bag which I hadn't opened to avoid risk of damage until ready to do the job (anyone ahead of me yet?). Anyway having now managed to contact the supplier (after a few days trying) they told me that the copper side is uppermost and the silver/steel side is the bottom - this confused me until I opened the bag....... the orange made both sides look copper - :lol:

Edited by Rod1883
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