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MG TD TF 1500 - What are these scratches?

All are on a single piston that the rings looked good and there is no apparent scoring on the cylinder walls.

John Redman

2nd picture.

John Redman

3rd picture

John Redman

How is the cylinder wall of the piston. Any scrapes on that?
David Honness

I would call that scuffing due to lack of oil, or overheating of the engine.

Tom Lange
MGT Repair
t lange

John,

I note that all the scratches are directly below a hole to feed the oil ring.

This suggests to me that somehow something abrasive got in the oil, sand, metal chips ???
I would make sure that nothing is embedded in the cylinder or the wall

Do any of the other pistons show similar scrapes?

If not then It may be a ring shedding chips
Don Harmer

Look like blow by to me.

Remove any ridge on the cylinder.
Hone the cylinder
New rings on that piston.

Jim B.
JA Benjamin

Before you do anything : measure bore and piston and post it please . De-glazing cylinder won't hurt.
Would like to know which cylinder we are talking about . 1 or two . 3 or 4.

cheers,

Gerard
Gerard Hengeveld

It is either 2 or 3. There is no apparent scoring of the cylinder walls and the scratched areas are about in thirds around the piston. The rings look dandy, all of them. I'm not using these pistons or the XPAG block anymore as I'm in the course of switching to the XPEG block I have been trying to sell for the last 4 years (unsuccessfully). The new pistons are new and the block liners are virgin. The only thing I can add is that the wrist pins in all of these pistons slip sideways more easily than I am used to.
John Redman

John,wrist pins slip side way's : interesting ! I am thinking more in to : block crank bores not right aligned , or / and con rods twisted . and hopefully not !!!! hidden crack in the crankshaft which allows the crank to flex. This all brings me to the question WHY did you take the block apart.

Respectfully,

Gerard
Gerard Hengeveld

As I said, I'm switching engines, using internal parts from XPAG to put into XPEG block where appropriate. All flexing aside, the rings, oil and solids, have the job of keeping the piston aligned inside the cylinder, yes?
John Redman

Keep us posted about the outcome with wear and tear after driving the Switched parts for about 6 to 700 miles.

Success Gerard
Gerard Hengeveld

Just a thought...
Could the scratches/marks have been incurred before a rebuild done by PO?
Bob;
RwB Brown

I know as it stands right now were all guessing, but if it's just one piston and the rest are normal, my guess it's possibly carbon damage. This doesn't take long to occur, once started, it can happen pretty quick. Are the oil holes above the scar marks plugged? Dirty oil with detergents burned out of it can cause wear patterns. I've also seen this in very old tractors engines, where non detergent oils were used along with ultra low quality fuels creating excessive carbon build up and hot spots. Does this piston have the same casting marks as the rest? Surprising the cylinder wall has no markings. PJ
Paul sr

I will check out the oil holes tomorrow. This oil (all Penzoil except one change by a garage putting in the roller cam) has never had a chance to get dirty. Any darkness is due to a moly additive. However, this may be a pre-existing from DPO as I've not torn this down this far before.
John Redman

John,

Looks very much like lubrication failure due to over temperature. Maybe a too efficient oil control ring or inverted oil control ring if possible. Saw similar damage in motorcycle engines years ago. Steyr- Daimler-Puch was famous for this failure. What do you think Gerard?

Regards,

Jim Haskins
J. M. Haskins

Pretty typical piston galling most often as result of overheat. This one could have been a bit tighter than the rest. Lucky if there truly is no bore scoring-saving another XPAG is a good thing.
Dan Craig

I'd say a clearance issue initially, then if that engine is running just a little hot either through timing or carb problems, you'd get some scuffing like that. For one cylinder to have a lube issue would see strange on these motors IMO.
L Rutt

I certainly can not lay aside the possibility of an overheat problem, one, because several of you have advanced that and two, because this whole process started with an overheat problem. It seems that just hitting 105 on the gauge can do this?? Anyhow, I have a new block, new pistons, new high capacity water pump, new radiator, removed thermostat (until winter), it CAN'T happen again?
John Redman

My guess is that that piston partially seized for whatever reason.
Chris at Octarine Services

Could have had an intake manifold leak on that cylinder, causing running lean and localized overheating? Looks exactly like two stroke motorcycle pistons after seizing from lack of oil, overheating, etc. George
George Butz

If the tolerance is not right, no matter how careful you are it will seize so make sure you do the proper checks. It is quite a process to measure bore and piston through out their lengths at diffent locations and orientation to make sure you have the right fit.
L Rutt

John, why remove the thermostat? Regards, tom
tom peterson

I think we would all be interested to hear what your local machine shop has to say about the marks.

Tom
t lange

Hi John,
I did the same switch as you are doing about 5 or 6 years ago. I put around 5000 miles on the motor and the only problem I had was with the rear oil seal. The engine performed beautifully, with the extra torque making all the time and energy invested, worthwhile. You will be amazed at the difference between the two blocks. I set the maximum revs to 5000 due to the TD rods. Be sure you get all the required parts balanced.

I do have one question for you. You refer to "block liners". What have these to do with the XPEG block?

George
George Raham [TD4224]

John,

looks like insufficient lubrication to me.

Have you checked out that the con rods went into the engine the right way round? They fit in both positions but are dedicated to be fitted with the pinch bolt to the RHS of the engine/car!
Installing the rods the wrong way around is possible but this will put a momentum on the pistons forcing them unequal to the sides of the bore.
Have a close look upon the pistons geometry! Although they look symmetrical with the wrist pin hole in the center, these holes are slightly offset and new pistons of these type are usually marked 'FRONT'.


Ralph
R.S. Ralph Siebenhaar

This thread was discussed between 21/09/2013 and 25/09/2013

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