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forged pistons


wrxhoon
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Just been through this for the 25. Rocket http://www.rocketindustries.com.au/ sell Arias forged for $1300 delivered in about 2 days with rings, floating pins and clips with most sizes on the shelf. I got 1.0mm or 40 thou OS that fast and they are well recommended. Comes complete with sizing info for the builder.

I know the GTR pistons are exactly the same diameter (86mm std) and configuration but lower CR (8.5:1 vs 9:1 in 25t) and was considering the stock nissan GTR ones which work out to $120 ea + rings (about $250) so almost the same price. I stuck with std CR due to driveability and only one big turbo etc. Nissan Oz can get them in for you in about a month. They also have on the shelf belt kits etc as well as gasket kits available either on shelf or order.

Hope you find a good builder and get the full balance etc. Don't forget bearings either. Apparently RB30 will fit and are cheaper. Sydneykid advised of the RB30 bearings. I have been told the mains are good but the BE's are weak and have to confirm this with "the 'kid"

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thanx for the quick replay skyline geoff .

i can get pistons and gaskets from nissan i'm well aware of that ( as a matter of fact u can get anything u want from nissan to suit the skyline ).

i just wanted to price the forgies for 2 reasons . first the max o/s u can get from nissan is +1 mm ( 40thou) my bore is badly marked so i may not be able to get away with that , i may have to go to +1.5 mm and i know u can get some forgies +1.5 .

second forgies are stronger and probably a little lighter .

if i can get them for $1300 (its only $300 more than nissan cast )then for sure i'll go the forgies .

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nissan Rb26 = forged pistons stock (high silicone)

1.5mm is a badly melted block....

:(:D:(

wrxhoon, just be careful because apparently there isn't much meat between cylinders to play with... I'm putting 40 thou oversized GREX pistons in mine, but was considering only 20 thou Arias to leave more meat there...

If you have bore damage, and want Arias pistons, then it's probably best to wait until the engine is dismantled and checked to see just how much you need to bore it out, and only do what's necessary...

That said, HKS sells 88mm pistons (80 thou over) so with a competent machinist, you SHOULD be okay if you need to go that far...

Good luck!

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field rb26 stock pistons are cast .

r32 gts do u know what the compression is with the arias ? is it still 8.5 to 1 ? where did u get them from ? how much ?

merli no prob with boring the block 60 thou plenty of meat there .the engine is dismantled now thats how i know that i have to bore it at least 40 thou maybe 60 u cant tell until u machine it if 40 will clean it up , if it does then i'll use 40 that way i have more options plus i can use stock h/gasket .

its not badly melted block its got 20 thou over now so another 20 thats 10 thou realy is not much .

thanks for the replays guys .

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Ok, do this.

Grab your old pistons and smash them with a hammer.

If they crack, it is cast

if they dent, they are some type of forging.

They do not look forged- same as the STI pistons.

Another thing to keepin mind is that what cast piston would hald 24 PSI boost?

You often see GTR's running fairly decent boost on stock internals.

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What has boost got to do with destroying pistons???? detonation destroys pistons.

Just wondering how many forget pistons you have belted with a hammer? Strange, every mechanic and engine builder I have spoken to tell me forget pistons are more brittle than cast.

wrxhoon, a guy on the rb30 conversion thread, very recently, posted up that he can get weisco pistons for 1K with rings, pins, clips.

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It is interesting, forging and casting are manufacturing processes, and have absolutely nothing to do with what alloy they are made from.

There are various grades of aluminium used in pistons, the main difference being the silicon content.

Low silicon content means soft, expands more with heat, and they deform before they break. They will take a lot of punishment, but require more running clearance.

High silicon is a harder material, and expands less, always used in cast stock pistons because you can run very tight clearances. Only problem is they are brittle and can snap ring lands at the first sign of serious detonation.

Forged pistons are sometimes available in alternative material. The big clue is the recommended running clearance. Another clue is the piston weight. Do your research and know what you are buying.

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I was told of these suppliers of great pistons and even contacted some, with bugger all response. The Rocket Arias pistons were delivered in a couple of days and were about 20-30 bucks for postage. Definitely worth a little extra for no runaround. I have no issue with guys online trying to do a little extra to help others, but it may be an unreliable solution.

Talk to the guys at Rocket and ask what sizes they have but definitely wait until you have pulled the engine apart and know what you need. I first rebuilt mine and had trouble with massive blowby. My reco-er said 0.5mm OS and I was suspecting the rings were not right. a few days ago i decided to buff up the worst broken piston that I had kept and found an 05 on the top under all of the crud from driving 2500 km on 4 broken slugs. Yep they were already OS 0.5mm and the dumb bastard got the same ones and fitted them up when the bore was badly scored.

Point is - check the top of your pistons yourself and see if there is 00, 05, 10 or any other numbers there.

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i'm in sydney so are rocket industries so no problem there .the engine is out and stripped so i know the bore is stuffed and its already got .5mm o/s (20thou) the marks are fairly deep on 2 bores and until we bore it out u can tell if +1mm will be enough and u cant realy bore it out without having the pistons so catch 22 situation . i'm doing the rebuild myself so i dont have to go to any idiot to do it for me . the reason it stuffed up was because the idiot that i took it to get a pink slip ( anual thing in nsw ) has to take the car for a run and get a brake test reading with a machine in order to get it reregistered for a year , well he decided to give it a floging the rear turbo busted the shaft and all the pieces from the turbine went in the engine and stuffed it all up . i checked rockets website and they have 87mm pistons (+1mm o/s ) they dont have 87.5 but wiseco have 87.5 i'll have to find the australian distibutor for them just in case i have to use 1.5 o/s .do u know if the rings the come with are chrome ?( usualy only top ring ) chrome rings need more agresive honing otherwise they never bed in .

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I was told of these suppliers of great pistons and even contacted some, with bugger all response. The Rocket Arias pistons were delivered in a couple of days and were about 20-30 bucks for postage. Definitely worth a little extra for no runaround. I have no issue with guys online trying to do a little extra to help others, but it may be an unreliable solution.

Talk to the guys at Rocket and ask what sizes they have but definitely wait until you have pulled the engine apart and know what you need. I first rebuilt mine and had trouble with massive blowby. My reco-er said 0.5mm OS and I was suspecting the rings were not right. a few days ago i decided to buff up the worst broken piston that I had kept and found an 05 on the top under all of the crud from driving 2500 km on 4 broken slugs. Yep they were already OS 0.5mm and the dumb bastard got the same ones and fitted them up when the bore was badly scored.

Point is - check the top of your pistons yourself and see if there is 00, 05, 10 or any other numbers there.

My rb** block (:() had 05 on the piston tops and all measured std bore. Same with rb20 block, had 06 on tops of pistons and is std bore.

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tnx andrew i know kristof and ben i think the price will be to high from them though but i'll give them a try .

bl4ck32 the 05 on ur pistons followed by a letter is an id mark .standard pistons have a dot , thats the front mark followed by number 1, 2 or 3 thats the grade followed by and id mark followed by a pin grade .

o/s pistons have 50 ( .5 o/s ) where the grade mark is on standard pistons .

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Simple. Get a set of verniers or a micrometer and check the pistons and/or the bore. You cannot afford to guesstimate these things - mechanics/engineers especially.

I've made the mistake of assuming a size on blocks/pistons, only to find out later I was mistaken, and have ordered the wrong parts etc (some of which could not be returned). Not only cost me money( in the form of parts and time) but precious time that I don't have!

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