How to Fix,Balance and hang Pistons

[BogusSVO]

How to fix mild pre-detonation on forged pistons.

The subject pistons are Wiseco pn 6595M85
+14 cc dish pistons w/ H.D wrist pins
03-07 Evo VIII

The pistons came into my shop with slight damage around the thin wall of the eyebrow on the outer edge.
They were hung on Eagle rods.
To me it looked like hot spotting and pre-det.

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Notice the damage on the outer edge of the piston?

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the first step is to remove the piston from the rod.
That is done by removing the C clips from the wrist pin bores.
Be careful not to bend or deform the clips, or you will have to order a new set form the piston manufacture.

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Next is to mic the piston to make sure it is within spec.

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Next using a small burr I ground away the damaged aluminum

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After that I used a flapper wheel to smooth any rough spots and to remove the galling

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I also removed the sharp edges (90*) that was from the machining of the piston when it was first made to help eliminate and more hot spots.

Next the pistons were glass beaded clean.

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Now to maintain balance, the piston were weight matched within .2 grams

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Next I checked the balance on the rods, starting with the small end.

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After all the small ends were matched.

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I balanced the overall weight of the rod, also keeping the balance with in .2g .

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Now it was time to hang the pistons on the rods.

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I start by installing one of the clips in each piston.

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After that is done, I oil the wrist pin bores in the piston.

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Also oiling the small end of the rod.

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Then oiling the wrist pin

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Then sliding the wrist pin through the piston and rod, Making sure the piston faces the proper way on the rod.

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The last step is to install the other wrist pin clip and making sure that all clips are seated in their grooves and the rod floats smoothly on the wrist pin.

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[Strm Trpr]

Excellent write up again.

I understand why the pistons have an orientation relative to the valves, but does it matter which way the rod is connected to the piston and crank just as long as the valve reliefs match up with the correct valves?

Do connecting rods have a rotational direction like uni-directional tires?

 

[crimsondragon]

If it was me, I would have checked the I.D. of the bushing of the small end of the rod journals and match them to the corresponding wrist pin O.D.

 

[BogusSVO]

the pistons, as told to me, came from an engine that had less than 2k miles

I did mic the wrist pins they were within .0003 from Hi to low
No notcable wear in the bushings or wrist pins,
Every thing went together smoothly, no "sticky spots"

Strm Trpr.... Thanks!

as far as 4cyl rods go, for the most part, they are not off set, that is built into the piston, so the rods can be flipped around with out worry of damage, as long as clearances are maintained, on a V8 with a crank that shares a rod throw, there is a diffrence in the way the rods face. due to the way the rods are beveled and the radius of the crank

 

[Strm Trpr]

as far as 4cyl rods go, for the most part, they are not off set, that is built into the piston, so the rods can be flipped around with out worry of damage, as long as clearances are maintained

Are some wrist pins offset horizontally to help with piston to wall thrust wear, or piston rock due to short piston skirts?

on a V8 with a crank that shares a rod throw, there is a difference in the way the rods face. due to the way the rods are beveled and the radius of the crank.

Yep, I definitely understand that.

 

[BogusSVO]

normally the off set is built into the piston, by the location of the wrist pin hole

the center to center is maintained in the coon rod, that way the force/power travles liniar through the rod and will not side load one side of the rod over the other.

 

[Strm Trpr]

Figured that much.
Do our 2.0L 4G63 have any wrist pin offset from the factory?
Do 2.3L pistons have wrist pin offset?

 

[BogusSVO]

That is not somethink I know off the top of my head. But i can look into it and let you know my findings.

That may be something the piston manufacture decides on when they first go into the piston design.

I know my Diamond forged ones have a slight amount of off set,(.003) but they are customs and not off the shelf.

 

[Strm Trpr]

Does that 3rd pic you posted show wrist pin offset?
If you measured across from the OD of the piston to the inner surface of the wrist pin bore, the measurement should be the same if the wrist pin isn't offset.

It appears like it's offset based on the amount of the flat on either side of the wrist pin, or is that an optical illusion?

 

[BogusSVO]

the way your talking apout measuring, it sounds like that should work.

I just dug up my Sealed Power Piston catalog #604 (2002)
Looking up the specs on the pistons, there is no metion of wrist pin off set

Piston part numbers 13507P 13510P

Both are for the 4G63