21 replies to this topic

[BaronVonchesto]

Took the head off to try and see why coolant is going into cylinders 2 and 3. Havent been able to spot the problem and will make another post with high res pics for that. However I was shocked to find deep scoring on either side of bore number 1:

 IMG_3445.JPG   77.86K   4 downloads

 IMG_3448.JPG   54.2K   6 downloads

 

The scoring is pretty deep. could be as much as a millimeter in depth using my finger to judge.

Considering the location of the scoring on the left and right of the bore (in line with the crankshaft), I suppose 1 one the circlips has come off the piston causing the gudgeon pin to wobble about in the bore? Has such a thing happened before?

 

More importantly is my engine block a goner? or perhaps i might need to get it sleeved?

or is there ANY chance i can avoid taking the engine out of the car? I just rebuilt it in 2019 and it has maybe 20k miles on it. Its honestly rather distressing...

 

With the piston at tdc there is absolutely no wobble.

[KTS]

...definitely engine out i'm afraid.

 

you'll need to take the block to the engine shop so they can measure and advise whether it's scrap or not..

[Spider]

Looks like the Gudgeon Pin has been going for a walk.

 

You'll likely find it can be bored a few sizes up or if it's beyond that, and you wanted to keep the block, it can be sleeved.

[ACDodd]

Yes the gudgeon pin has moved and hit the bore wall, engine rebuild time.

Ac

[BaronVonchesto]

damn. more unplanned for expenses, and with my current job i have no time to do the engine myself 

 

What can I do to make sure the gudgeon pin doesnt move again?

 

This certainly explains why my last oil change was FULL of swarf

[BaronVonchesto]

Looks like the Gudgeon Pin has been going for a walk.

 

You'll likely find it can be bored a few sizes up or if it's beyond that, and you wanted to keep the block, it can be sleeved.

 

Bored the block to +040 when I rebuilt it in 2019. Really don't want to change pistons again so soon. Would it be okay to just sleeve cylinder number 1 that has the problem? Seeing that the other cylinders are just fine?

Edited by BaronVonchesto, 15 February 2023 - 04:48 PM.

[DeadSquare]

You can certainly just sleeve the one cylinder, but might have to use something other than a Classic Mini sleeve, as these days the wall thickness of sleeves is getting thinner and thinner, but that is the machine shop's problem to sort out.

[ACDodd]

You need to replace the conrod and verify the fit of the gudgeon pin in all the rods. The trouble is some engine builders vastly over heat the little end of the rod when they fit the pistons, which softens the rod and reduces its interference fit on the gudgeon pin. So, to fix, find 4 rods that have a good interence fit in the gudgeon pins, 0.0015” is the target to aim for. Then have the rods hardness tested to ensure they are around 30HRc any
That are 25HRc or less replace.

Ac

Edited by ACDodd, 15 February 2023 - 07:58 PM.

[BaronVonchesto]

You need to replace the conrod and verify the fit of the gudgeon pin in all the rods. The trouble is some engine builders vastly over heat the little end of the rod when they fit the pistons, which softens the rod and reduces its interference fit on the gudgeon pin. So, to fix, find 4 rods that have a good interence fit in the gudgeon pins, 0.0015” is the target to aim for. Then have the rods hardness tested to ensure they are around 30HRc any
That are 25HRc or less replace.

Ac

 

mine were interference fit conrods, but I had them modified in 2019 as the new pistons I bought were the floating pin type that are held in with circlips.

 

I think the reason this may have happened was because I lost one of the circlips and bought a different circlip of approx the same size and fit it in.

[BaronVonchesto]

Looks like the Gudgeon Pin has been going for a walk.

 

You'll likely find it can be bored a few sizes up or if it's beyond that, and you wanted to keep the block, it can be sleeved.

 

When rebuilding the engine, I lost one of the piston circlips. As i was trying to fit it in it went flying off somewhere and I could never find it. I went to the hardware store and got a replacement circlip of the same size, fitted it and never thought twice.

 

I don't remember which piston I fitted the circlip to, but seeing that its cylinder 1 thats knackered, I'd bet money that I fitted that circlip to piston 1.

 

So the big question is... can I get replacement piston circlips??

[Spider]

 

Looks like the Gudgeon Pin has been going for a walk.

 

You'll likely find it can be bored a few sizes up or if it's beyond that, and you wanted to keep the block, it can be sleeved.

 

When rebuilding the engine, I lost one of the piston circlips. As i was trying to fit it in it went flying off somewhere and I could never find it. I went to the hardware store and got a replacement circlip of the same size, fitted it and never thought twice.

 

I don't remember which piston I fitted the circlip to, but seeing that its cylinder 1 thats knackered, I'd bet money that I fitted that circlip to piston 1.

 

So the big question is... can I get replacement piston circlips??

 

 

You should be able to get a decent circlip the same as that that was lost. As well as diameter, they do vary in thickness and so need to check that too.

There is a right and wrong way to fit the clips. They are made by stamping them out of a sheet of steel, so they have a rounded side and a 'sharp' side. They are always fitted 'sharp' side out, that way, they 'bite' in to the circlip groove and so less likely to come out. I also always fit them with the 'ears' on the clips either up or down - never sideways. If you are careful with loctite, you could also put 1/4 of a drop on each clip, but be sure it doesn't get on the pin.

[BaronVonchesto]

 

 

Looks like the Gudgeon Pin has been going for a walk.

 

You'll likely find it can be bored a few sizes up or if it's beyond that, and you wanted to keep the block, it can be sleeved.

 

When rebuilding the engine, I lost one of the piston circlips. As i was trying to fit it in it went flying off somewhere and I could never find it. I went to the hardware store and got a replacement circlip of the same size, fitted it and never thought twice.

 

I don't remember which piston I fitted the circlip to, but seeing that its cylinder 1 thats knackered, I'd bet money that I fitted that circlip to piston 1.

 

So the big question is... can I get replacement piston circlips??

 

 

You should be able to get a decent circlip the same as that that was lost. As well as diameter, they do vary in thickness and so need to check that too.

There is a right and wrong way to fit the clips. They are made by stamping them out of a sheet of steel, so they have a rounded side and a 'sharp' side. They are always fitted 'sharp' side out, that way, they 'bite' in to the circlip groove and so less likely to come out. I also always fit them with the 'ears' on the clips either up or down - never sideways. If you are careful with loctite, you could also put 1/4 of a drop on each clip, but be sure it doesn't get on the pin.

 

You see, I didn't know that the circlip had a right and wrong way to be fitted! Though i think it would be obvious when fitting?

Anyway I bought extra circlips (always buy 3x the number of bolts, nuts, washers , circlips etc because those buggers always go missing!).
Just checked them and they are flat on both sides. No sharp edge. Should I consider grinding down one edge slightly to make it sharp?

[Icey]

Before ruminating over the finer details, I think you need to pull the piston/rod out and inspect. It could be as simple as the snap ring you fitted was the wrong size and has been driven out of the grove by the movement of the wrist pin. Until you've seen the actual failure there's no point in speculating (although fun to do from the comfort of a phone/laptop screen).

Edited by Icey, 16 February 2023 - 12:11 PM.

[Spider]

Just checked them and they are flat on both sides. No sharp edge. Should I consider grinding down one edge slightly to make it sharp?

 

I wouldn't be trying to grind in a bur on the clips, I doubt you'd keep the shape doing them by hand and it will make them thinner in section reducing they spring tension.

 

Where ever those were made, they probably deburred them for today's touchy-feely brigade,,,,,,

I would not be fitting clips that didn't have at least a flat square side, if they had any radius on one side, I wouldn't fit them.

You might need to follow some up from a Piston or Industrial supplier, I'm not sure I'd trust any from a Hardware, the consequences as you've found, are too great if one come out.
 

[Spider]

They talk about the circlips in the ACL Engine Manual here;-