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MG MGB Technical - de-coking engine

I've had my MG BGT (1970) for about a year now, gradually repairing/replacing bits as required. During all that time, it's run well but always burned a lot of oil. I have tried the breather pipe at sump level, replaced the pressure release value spring and mount but in the end have been forced into a decoke and rebuild.
Now the fun begins, I removed the head, and found the cylinders, head and values covered in about 1mm of coke (burnt oil etc)- I joke not!.
Question is how best to remove the muck - wire brush?, detergent (which one?) wooden spatular?.... Secondly, I guess I will need to re-grind the values, and was thinking just grinding paste - but will this do the job?. Bizarely the stems and seats actually look OK, its just the bit visible from the head that is covered by deposits.....
Any thoughts anyone?

Mike
M Kemp

Mike, If you have that much coke in your motor it seems reasonable to expect that this could be as a result in oil coming up past the piston rings and burning in the cylinders. Unfortunately you don't tell us how many miles the motor has done or when its last rebuild was but at the very least copious quantities of oil are coming from somewhere and it seems that there is too much for it to be only coming down the valve stems due to poor seals. Try to get an idea of how much bore wear there is in the motor and once you know this then will be the time to decide on the next action
Iain MacKintosh

Mike

See also the comments in the concurrent posting "cylinder head/valve stem" initiated by Ken Harris.

Regards,

BarryQ
B.J. Quartermaine

Thanks for your comments.
I should have mentioned that the car has done 74,000 miles without any rebuild of the engine. My intention was to replace the cylinder rings, but the level of coke and how best to remove it without damaging the pistons and values led to the question.
M Kemp

If you were considering replacing the rings all well and good. Depending on the amount or bore wear this should effect a cure provided that wear does not exceed about .005" 74,000 miles seems to be a reasonable interval and one at which the engine would benefit from an interim overhaul. Consider replacing the big end shells at the same time.
Iain MacKintosh

Carb cleaner should soften the carbon making it eaiser to remove. You can wire brush the head and valves but don't wire brush the pistons as it is easy to start removing aluminum. I would have valves ground, grinding paste will not remove the wear that has occured from 70k miles of driving. Have the seats replaced and new hardened exhaust valves installed to make a no lead head.
John H

This thread was discussed between 28/03/2007 and 29/03/2007

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