Ls7 Piston orientation

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Aug 8, 2022 | 08:48 AM

#41

FormulaBoat

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Quote:

Originally Posted by psicko

Why would the rods need to be installed in a certain orientation?

Typically one side of the rod big end has a chamfer to match the fillet where the crank journal meets the counterweight.

Aug 8, 2022 | 08:52 AM

#42

psicko

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Quote:

Originally Posted by FormulaBoat

Typically one side of the rod big end has a chamfer to match the fillet where the crank journal meets the counterweight.

Not on stock LS stuff. Stock LS crank journals have rolled fillets, not a radius, so a chamfer isn't needed on the rods or bearings.

Aug 8, 2022 | 08:58 AM

#43

FormulaBoat

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Quote:

Originally Posted by G Atsma

It has to do with rotation, so the offset would go to the same side regardless of which bank they're on. It's either all left or all right depending on which end you are looking from.

Mostly. I build reverse rotation engines, and this is one of the key consideration points in doing so. All the marks will either face forward or rearward, regardless of bank.

The offset is to keep the piston from rocking in the bore and wearing quickly or being noisy. It essentially keeps the piston always "cocked" one way in the bore. For conventional rotation direction, the dot/notch on the piston top should face forward on each bank, this is why production pistons have symmetrical valve reliefs cut into them, to be used on either side. There have been studies of installing these backward to make more power due to changing piston dwell, and have supposedly shown gains, but the longevity tradeoff is then a concern.

Last edited by FormulaBoat; Aug 8, 2022 at 09:10 AM.

Aug 8, 2022 | 09:08 AM

#44

FormulaBoat

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Quote:

Originally Posted by psicko

Not on stock LS stuff. Stock LS crank journals have rolled fillets, not a radius, so a chamfer isn't needed on the rods or bearings.

Just checked, looks correct. Why do the stock LS rods have dimple identification then?

Aug 8, 2022 | 09:16 AM

#45

psicko

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Quote:

Originally Posted by FormulaBoat

Just checked, looks correct. Why do the stock LS rods have dimple identification then?

I don't know, but if I had to guess, I would say it has to do with the manufacturing process. Maybe it is a point where the powdered metal is poured into the mold?

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