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MG TD TF 1500 - Remove carbon on top of pistons

MG midget workshop manual chapter 1:5 starts as follow: "If the tops of the pistons have not already had the carbon removed, remove all the carbon except for that on the outer edges. A piston ring placed in the bore on top of the piston while scraping will prevent the outer edge being touched"

What's your position on that subject? Would you as well recommend doing that?
Thanks for your comments.
Cheers,
Guenter
Guenter

The carbon on the edge is part of the seal that is needed to prevent blow-by. In fact, I probably wouldn't remove any carbon at all, as its mass will contribute to a small increase in compression ratio.

In my humble opinion, the advice is spot-on.

Gord Clark
Rockburn, Qué.
Gordon A Clark

De-carbonizing pistons is one of those things that have different camps. Most car companies of the vintage of MG routinely recommended de-carbonizing or de-coking as it is also known as.

As I understand it, deposits of carbon on the piston can get red hot and cause improper detonation of the fuel. This can also cause run-on.

I normally check the carbon on the TD about every 10,000 to 15,000 miles. But it depends on how your individual engine is working.

I put the piston up top,and then put vasoline in the groove between the piston and the cylinder. This catches all the particles. Then I use a fine wire brush on a drill motor and take the carbon off. (I put rags in the other cylinders to stop the dust getting in them.)

When Done, I vacuum the piston and the edge to get all the carbon out. Drop the piston down and wipe out the vasoline with the rest of the particles.

Know there are a number of other ways to do this and others will say what they do.
Bruce Cunha

I routinely de-coke marine engines (2 cycles) because the carbon build up can cause both detonation and snap a ring if it sticks in the grove. I use SeaFoam, which is basically naptha, run in to the fuel system.

You could do the same with the TD, but as Gordon says, you want the ring of carbon at the outer edge. So, I don't decarbonize the TD unless detonation is noted.

warmly,
dave
Dave Braun

This thread was discussed between 02/05/2010 and 03/05/2010

MG TD TF 1500 index

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