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Best Place To Remove Weight On AA 94 B Pistons
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bugguy1967
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PostPosted: Sun Oct 12, 2014 8:47 am    Post subject: Best Place To Remove Weight On AA 94 B Pistons Reply with quote

As the title says, one of my pistons is .9 grams heavier than the rest. I've already swapped around ring stacks and pins to get the closest numbers, so I need to remove material. I'm using a good quality scale, so my numbers are accurate.

Is there enough material on the underside of the crown to mill a little, or should I be just chamfering the inside edges of that piston? I could also cut away at the inside of the pin on a lathe. What's the preferred, and most professional looking method?

Also, in a running engine, does it make a difference to the connecting rods where the weight is (pin, piston, rings)? So, if I have a piston on #1 with a 300 gram piston and 50 gram rings, and a piston on #2 with a 280 gram piston and 70 gram rings, is the load on the rods still the same?
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modok
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PostPosted: Sun Oct 12, 2014 11:40 am    Post subject: Re: Best Place To Remove Weight On AA 94 B Pistons Reply with quote

bugguy1967 wrote:
So, if I have a piston on #1 with a 300 gram piston and 50 gram rings, and a piston on #2 with a 280 gram piston and 70 gram rings, is the load on the rods still the same?


Correct! When you can't fix the piston, then we make a special pin.

1 gram is no problem. If there is no low hanging fruit just shorten the skirt all the way around, freehand.
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Casting Timmy
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PostPosted: Sun Oct 12, 2014 11:43 am    Post subject: Reply with quote

I think you could also put the heaviest two pistons on the front cylinders and the lighter two on the rear and just do minimal weight removal to get to matching piston/rings/pin
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Casting Timmy
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PostPosted: Sun Oct 12, 2014 11:45 am    Post subject: Reply with quote

I've also wondered if anyone cuts down the skirts just to make all the pistons lighter at times? I know some pistons are shorter than others, but the shorter pistons can sometimes have a shorter life span.

I've thought about cutting my skirts down a little to reduce weight since the pistons and cylinder kits from AA aren't a bad price at all.
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56vwoval
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PostPosted: Sun Oct 12, 2014 11:49 am    Post subject: weight Reply with quote

Just bought a set of AA 92's and all four were within one half gram of each other.
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andy198712
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PostPosted: Sun Oct 12, 2014 12:41 pm    Post subject: Reply with quote

yeah mine were really close.

before i have removed material from the inside of the pin, it doesn't take much, weight of steel vs ally...
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bugguy1967
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PostPosted: Sun Oct 12, 2014 4:15 pm    Post subject: Reply with quote

I'm usually able to get them within .05 grams with parts swapping, but with this set, .09 is the best I could do. I'll remove from the pin on the lathe then.
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mark tucker
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PostPosted: Sun Oct 12, 2014 7:51 pm    Post subject: Reply with quote

I never remove material from pins to balance piston,and never under the dome either. there is usualy enough flash or places to remove material.if you do some skirt work be sure to leave a sharp edge on the outer dia so it sheers off the oil from the cylinder,not tapered so it funnels it to the rings witch will be over whelmed. I supose a slight inside chamfer to the pin would be ok to tget the pins the same. above the pin on some pistons is a good place to get some too.
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bugguy1967
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PostPosted: Sun Oct 12, 2014 8:27 pm    Post subject: Reply with quote

Yeah, I was only thinking of doing an inside deburring around the inside of the piston, not the outside. Also I wouldn't want to shorten the pin by taking material completely off one side. I was only considering taking out enough from the inside to remove .5 grams.
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mark tucker
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PostPosted: Mon Oct 13, 2014 8:48 am    Post subject: Reply with quote

Ive never had an issue with pins not being the same weight,but Ive mostly used JE,manly,wizeco. witch is a totaly different ballgame then these things. if it is a straight through hole you could possiably hone it if you had a pin hone. or like stated befor a slight taper on the id. I dont remember how far out my aa 92's were. but I did a good bit of work inside them.
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