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MG MGB Technical - Wrong pistons marque...

See my previous threath "advice after compressionstest" bad results by compressiontest.

I found the problem. I pull out the motor and begin to check everything. Afther a day I found the problem an you cant believe!!!

The pistons are marque oversize 060... The bore in the engine is at the right size fore thise pistons...

But by controle the deminsions of the pistons the are not 060 but 020 oversize!!! Yes wrong marque... 4 pistons (result: bad compression, piston slap, etc)

Did anybody have the same problem in his live?
Meersman Paul

That is shocking!!! Thanks for posting as clearly this means before assembly 10 minutes with a vernier caliper can save days of work later on.
Stan Best

Paul,

i did not have this problem jet, but heared from a MG spare parts dealer that it is not uncommon when cheap overhauled engines form some of the 'specialists' are used.
Cosidre upon the costs of boring, honing, line boring and crank grinding, ballancing, checking con rods, new cam and followers, chain and spockets, pushrods, rocker assy, oil pump, valves and guides, lead free seats, gaskets, cleaning, painting and shipment and all that at 1500 to 1800 Euros and even have a margin upon it? Strange, isn't it?

Looks as if some of the engine remanufacurers just combine cleaned up used parts and do not hesitate upon quality...

If there is a valid warranty upon your engine, try to get an other one that is built to meet the specs of the workshop manual.

Good luck

Ralph

Ralph

Paul. I have never heard of such a problem with MGs. But, it is not uncommon in manufacturing that a part can be mis-marked. That is why, as Stan notes, any good quality machine shop or engine builder will check the size of the parts before using them or after installing them (thrust washers and rod/main bearings).

Les
Les Bengtson

Les,

it seems to be an other situation in continental Europe. MG's, even the B's are only used for fun by most of their owners and only log an averedge of 3 to 5k Kilometers a year and very few drivers know the limits of their engines. So what does a two year warranty count then and where is the risk for a dealer?
Most customers here want everything for their cars extremely cheap and get what they pay for.

When i do an engine for my B or the GTV8, machine shop work and parts cost almost twice the price a rebuilt unit is offered for here. So you are lucky to live where skilled craftmen do a good job in engine rebuilt, i think. These times have faded out some 25 years in here. When i had the last engine bored, just a year ago, i considered to by second hand machinery for the next overhault to do it myself, as this seems easier than to find a company in here, that is skilled for an overhault of a B-Series engine, 'that is so extemely difficult and delicate'.
Most of them are only used to swap parts but do not have any idea of what they are doing.

Within three decades of engine rebuilding, i never have had a problem with faulty marked internals or wrong dimensions of the items i ordered, not with parts for the MG's nore with those used for the marine engines too.

Ralph
Ralph

Ralph. We are seeing the same thing here in the US with our loss of our manufacturing base and declining economy. Adam Smith noted that manufacturing was the creation of wealth. We are not doing that much anymore.

Several years ago, I purchased a rebuilt engine for my truck when the existing engine through a rod. The first engine lasted 2K miles and was replaced under warranty. The replacement engine lasted 8K miles and was rebuilt by a better quality builder who found the cylinder bores were undersize, causing the pistons to collapse. Better to have spent twice the money and gotten a better quality engine--but, one was not available. You have to do it yourself.

My daughter's Miata needs the U joints replaced. The U joints are swagged in place. A local company used to be able to bore the old U joints out and replace them with a slightly larger U joint. Now, that U joint is out of production, they cannot be replaced, and a new drive shaft has to be installed.

Great commentary about modern times in the Western World.

Les
Les Bengtson

Ralpf - Les

I agree with you that a good machineshop controle all the deminsions of the parts. I dont blame the shop, this peoples build a few engine a day and have a "blind trust". And yes, I check all the parts and all the stuff was (is) new. Bad luck the guy's have. Good luck for me, after 2 years and about 5000 miles I have a full garantee - a complete new rebuild engine, without any problem with the shop. Kind people...

Kind regards

Pol

pol

Ralph,

What you have to remember is that reconditioners like myself buy parts in bulk and machine in batches so the costs of rebuilding an engine with the same parts you would buy retail is a fraction of what you would pay for a one off rebuild.

For instance, pistons that retail at £140 cost me £37.50 when bought in bulk!
Chris at Octarine Services

Paul

Where did you measure the dimension of the piston?

Peter
peter burgess

Chris, I understand where you are comming from but I bet that you at least check the piston clearence in the bore before assembly. In Paul's case one would have to be near brain dead to not notice that the bore was 0.040 larger then the piston. you could almost assemble that without a ring compressor.
John H

Chris,

i can understand that quite well and it is a very honest answer you gave. Seems that it was right when i quoted the Octarine-Services homepage several times on the local MG board www.mgdc.de.

Ralph

Ralph

John,

Each piston is measured just under the pin at 90 degrees to it and the matching cylinder is bored and honed to that dimension plus the recommended clearance of 2.5 thou.

Ring gaps are also checked for each cylinder and adjusted if necessary to 3 thou per inch of bore.

In practice, I find that the pistons I use are very consistent in size and all 4 bores are identical.

It is not unusual to have the wrong markings on pistons - there are some with the word "front" stamped on in the wrong place above the pin! - so to have some marked 060 which were actually 020 wouldn't surprise me, though I echo Peter's question as to how Paul has measured the piston as across the top land is narrower and also the piston is not circular, being narrower along the pin.
Chris at Octarine Services

Hello Guy's

I measured the pistons like discript in the technical books! And yes the stamp "FRONT" was 90° wrong - on de left side off the block... And I that always read in the books that the front of a engine is on the front from the car. I think that my english is not so good... Net time I buy a manual in Dutch!!!

Kind regards

Meersman Paul

Pol

This thread was discussed between 05/11/2007 and 08/11/2007

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