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Oversize 23rd July 2017 07:50 PM

6.9 Piston Weight
Anyone know or able to measure the weight of a 6.9 piston? Faced with a rebuild, would one be well advised to souce custom hi compression pistons made from lighter high strength modern materials? Would such a mod allow a M100 to rev higher and more quickly?? I remember reading a while ago about max piston speed that MB engineers were faced with during 6.9 development. Obviously they were concerned about durability and the pistons not coming apart but with that comes increased weight. Was the weight the main factor in the rev limit?

I heard 6.9 pistons also have an iron band for a reason unknown to me. Has tech & materials come far enough now that there's a better alternative to standard pistons?

I'm thinking of changing pistons in the future on an Aussie engine, but retaining stock rods.

motec 6.9 24th July 2017 06:35 PM

Re: 6.9 Piston Weight
Have it somewhere . Old pistons are sitting in my brothers garage in Perth. But they are attached to the rods. From memory they were close to 900grams where quiet heavy forged pistons rods are beefy as well. Only other person I know with them sitting around out off engine has a few in W.A

Oversize 24th July 2017 06:59 PM

Re: 6.9 Piston Weight
900g is almost 1kg! That's almost 8kg of weight spinning back and forth at 5K RPM! It has also been suggested by a clever person we could ask a part supplier! To be continued....

motec 6.9 24th July 2017 09:04 PM

Re: 6.9 Piston Weight
Give an idea my cast 292 Chevy pistons are 920 grams. Forged Ross 250 pistons are 488 grams . Forged 292 were around 580 something. That's why 250 pistons but need longer rods to use.

Oversize 25th July 2017 07:09 PM

Re: 6.9 Piston Weight
Apparently 6.9 piston & rod complete is 2220g?? Does that sound about right?

motec 6.9 26th July 2017 01:02 PM

Re: 6.9 Piston Weight
Yes picked mine up like that and they are quiet heavy . built like rods from a Hemi .

Oversize 26th July 2017 01:24 PM

Re: 6.9 Piston Weight
That's nearly 18kg of rotating mass not including the crank & torque convertor! Yikes...

motec 6.9 26th July 2017 03:32 PM

Re: 6.9 Piston Weight
Crank well at a guess its over 40kg probably closer to 50. As I said standard cast pistons for a 292 Chevy 6 are over 900 grams thats why I went with 250 forged at 488 grams.

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