The Forgotten On

Alright, so the time has come for me to balance some of the bottom end of my 5.0 hybrid build (not removing the crank, don't want to deal with resealing the block).

I removed all of the pistons, rods, and wristpins and so far have weighed the pistons and wristpins after having them fly cut.

Here are the numbers
Pistons

1. 576.7g
2. 575.8g
3. 574g
4. 576.5g
5. 575.5g
6. 575.9g
7. 576.2g
8. 576.8

Wristpins

1. 142.44g
2. 142.65g
3. 142.17g
4. 142.50g
5. 142.57g
6. 142.45g
7. 142.70g
8. 142.80g

After getting these numbers the heaviest is piston & pin #8 at 719.6g and the lightest is piston & pin #3 at 716.17g. A difference of 3.43 grams.

Which is just within Porsche's variance tolerance of 4 grams. But outside of their goal weight of 722g due to the machining.

I wanted to know if it is permissible to swap wristpins between pistons as Porsche says in the WSM in section 13-24a or would it be more advisable to just remove material with a dremel to within 1/10th of a gram.

Thanks everyone.

Lizard928

So long as the wrist pins are within spec I would say you are A-OK

GregBBRD

Used wrist pins are worn into each piston and visa versa. They are also worn unto each connecting rod bushing, BTW. Not only do not swap them, but don't even turn them around in a piston.

You can swap wrist pins in new pistons....or if you use new wrist pins in used pistons you can obviously swap them around.

....And forget that 1/10 of a gram bull****. The difference in carbon deposits after the first week of running is more than that! Hell, the variance in the amount of oil hanging on any given piston at any given time is more than that! Get every piston, pin, pin locks, and ring set combination with-in one gram and then work on the connecting rods....they are the things to really be concerned about.
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The Forgotten On

Sh*t, I let Engine Supply disassemble them when they fly cut them. I'll mic them tomorrow. My latest micrometer is good down to .001mm, that should show any excessive wear.

Either way, I'll relax on the tolerances and get them to within 0.5 of a gram. That way there can only be 1 gram max variance between the piston sets.