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  #16  
Old 10-21-2013, 05:05 PM
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I wonder if your internet seller is getting rejects? Factory seconds - that sort of thing. Just a thought.

Dan

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  #17  
Old 10-21-2013, 07:03 PM
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Quote:
Do not remove the steel pads, they control the expansion of the piston.

You could weigh the connecting rods and pair the heaviest piston with the lightest rod.
That would not be the best method. Rod balancing is done in two steps. The large end is considered as an assembly that rotates around the wrist pin then the small end is considered as an assembly that rotates around the crank pin. Simply picking a heavy rod and mating it to a light piston discounts the rod balancing procedure and doesn't resolve the piston imbalance.

A careful guy with an end mill in a drill press might be able to remove some material from the crown. Additional careful work around the pin boss with carbide burr then a sander in a die grinder will finish the job. Since these are not diesel pistons and they are presumably not subject to positive intake pressure they're likely to be plenty strong enough.
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  #18  
Old 10-21-2013, 08:07 PM
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Built a air cooled V.W. engine within 0,5 grams, and took a lot of fiddling, which I love. Need to do it again as used too much cam lift... Other than that, sounds and performs great!

First step is to weigh all your wrist pins separate from the pistons. I.I.R.C. they were five grams out, so every bit helps.

Machine shop said to take off a smidgen on each corner of the skirt. 0,25 on each corner isn't much and adds up fast.

Hope this helps, good luck, and most important, have fun!
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  #19  
Old 10-22-2013, 11:53 AM
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I think a difference of 20 grams is too much - the FSM says 10 grams max. Obviously I'd like them to be as close as possible.

The seller got back to me with a suspicious cut and paste bit of information from technical support saying that 20 grams was OK. I know it isn't. I'm not getting a good feeling about this seller - and I've never known anyone in technical support to reply that quickly. (Within normal working hours the reply must have been done within two hours) I smell a rat.
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  #20  
Old 10-22-2013, 12:07 PM
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are all the wristpins the same weight?

I'd certainly grind off the bumps, and thin out the skirts and any flash inside the heaviest ones...
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My drivers:
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  #21  
Old 10-22-2013, 12:08 PM
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have you considered that the pistons are actually knockoffs?
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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  #22  
Old 10-22-2013, 12:09 PM
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try contacting Nural directly...
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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  #23  
Old 10-22-2013, 12:13 PM
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Quote:
Originally Posted by vstech View Post
are all the wristpins the same weight?

I'd certainly grind off the bumps, and thin out the skirts and any flash inside the heaviest ones...
Sorry I forgot about that bit...

...yes...

Wrist pins are all the same weight at 108 grams.

I can't see 10 - 20 grams of weight difference in the rings which are still fitted. I don't want to remove them 'cos knowing my luck one or more will break and then I can't send them back.

I could indeed remove the obvious bumps but the inside of all of the pistons have been nicely finished - there isn't anything obvious to remove. The knobbly bit in the pictures on page one that was discussed previously has a weight about 2 grams (I know that from arsing about with my older M102.910 pistons).

{Please don't make me explain why I've bought new pistons!}
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1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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  #24  
Old 10-22-2013, 12:18 PM
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Quote:
Originally Posted by vstech View Post
try contacting Nural directly...
I think that will show that the seller hasn't been in touch with them and so it will start a Dutch "I mustn't loose face" situation which will mean that I will probably get shafted. At this stage I have learnt that it is best to go with the flow and only start the full on whinging when it is necessary.

I've shown the seller proof that what he has sent isn't within the specs in the FSM. I'm waiting for a response to "if you can't change them for other pistons that gives me a set of four within spec then I'd like my money back please"...

...tedious...

...it is always a people problem...
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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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  #25  
Old 10-22-2013, 12:18 PM
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how about the small end of the rods? is there a grinding pad on them?
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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  #26  
Old 10-22-2013, 12:19 PM
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when building race motors, we always balanced the assembly as a whole. balanced the small end with the piston, balanced the large end too... not sure why the pistons themselves would all need to be balanced separately...
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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  #27  
Old 10-22-2013, 12:30 PM
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as long as total recriprocating weight is equal, (small end of rod, wrist pins, and piston/rings) and rotating weight is equal (large end of rod, and rod bearing, cap screws)
you should be just fine.
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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  #28  
Old 10-22-2013, 12:30 PM
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Quote:
Originally Posted by vstech View Post
... not sure why the pistons themselves would all need to be balanced separately...
Because they are a heavy part that moves very quickly and stops very quickly at the end of each stroke!
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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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  #29  
Old 10-22-2013, 12:32 PM
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Quote:
Originally Posted by Stretch View Post
Because they are a heavy part that moves very quickly and stops very quickly at the end of each stroke!
see post# 27
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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  #30  
Old 10-22-2013, 12:33 PM
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the next question is...

are you balancing the weights to the original weight of the original parts? or are you balancing the crank too...

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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