Which Pistons For Xu9J4 Rebuild?

[unariciflocos 49 1 Cars]

So I want to do a full rebuild on my Mi16 with new liners aiming for a reliable engine.

 

I've bought a set of standard pistons on ebay, B's so 82.97 mm and the rods had ARP rod bolts and I've noticed that at one point they've been balanced judging by the machining marks. One of the pistons is however different from the rest and it's been heavily lightened, but is the same manufacturer. One of the rods is overheated and ovaled because of a spun shell.

 

In my engine I have A size pistons, never been balanced, bog standard.

 

My question is which ones to use with new liners? The rods will be mix and match due to spun shell damage on both sets.

 

Thanks,

Andrei

 

[petert 586]

Which ever ones fit the liners best. It's easy enough to balance again.

[unariciflocos 49 1 Cars]

Thanks! Guess I've got some reading to do on how to balance.

 

How would I determine which pistons fit the liners best?

[petert 586]

Take liners and pistons to someone with micrometers/bore gauge etc. There's no room for guess work here. The pistons are strutted, thus run fairly tight clearance.

[unariciflocos 49 1 Cars]

I can get hold of a micrometer and gauge meter, I don't know however what the tolerances need to be. I'm assuming the liners be perfect 83, since they're new...

[unariciflocos 49 1 Cars]

Just before putting the head back on I had a closer look at the piston in the fist picture and noticed that the valve cutous were not as deep as on the other pistons.

 

Since deepening the cutouts would have mean that I would have had to lighten all the rest of the pistons I decided to just use one of my other pistons that was exactly 466 grams as the others and just go with it. My even bigger concern was that I would have a had a much higher compression on that cylinder since I;ve machined the new liners for ~11:1 (0.6 mm skimmed from block and liners, liners were bushed at one end, coned at the bottom and used a lathe to scrape some material off the seat).

 

Hopefully I will not have any issues because 3 pistons are Bs and one is an A.

[B1ack_Mi16 67]

If some have smaller cutouts, are you sure you don't have some D6C pistons and some DFW ones?

 

DFW ones are slightly shorter and cutouts therefore looks smaller.

[petert 586]

The relationship between the depth of the cutout and the pin is the same between D6C (stamped Z) pistons and DFW (stamped X) pistons.

[unariciflocos 49 1 Cars]

The piston in the picture seems to have been bough new at a later stage, it has no Z or X or A, B, C markings, but it is however made by the same manufacturer. Engine is now closed, I'm seeing about 210 psi on each cylinder so for now I'm happy with that.

 

Just need to sort out why it's running on three cylinders and find a really nasty sounding lifter.