Dilemma

[GTS4WD]

there defiantly forgies. The piston you have are sold by precision performance. they retail for $1500. they are some chinese brand but dont be to worried there no to bad really. these are mine that we put in rb30's for a cheaper optioned rebuild. Just put it all back together and drive it, as lond as there not damaged it will be sweet. cheers

mate.. you are a legend!

I owe you a beer!

[GTS4WD]

well, what piston to bore clearance are you aiming for?

about .035mm - 0.055mm

Edited July 23, 2007 by GTS4WD

[T04GTR]

f**k thats loose!!!

[T04GTR]

make sure its not much bigger than .03 whats that in thou?

[turboedsloth]

.03mm=.0012"inch i think. or do you mean .03thou inch

[B0oStEr]

0.10mm or 4 thou of an inch is normal piston to bore clearance for some forgies.

Best to find out what the piston manufacturers recommend.

[proengines]

Those pistons are Hypatec liquid forged. They are a semi forged piston and are hypereutectic. They are sold by Precision International, they are not a bad piston though I haven't used them in any turbo engine.

More info here: http://www.precisionintl.com/HTML/product/...hypatec_lf.html

[Cubes]

Those precision hypatec's can be had over on ct.com for around $550 with anodized crown I believe.

A few of those blokes run them; s3girl here on SAU used to run them and made 470rwkw granted with water injection.

[GTS4WD]

0.10mm or 4 thou of an inch is normal piston to bore clearance for some forgies.

Best to find out what the piston manufacturers recommend.

thats a bit large..

why such a large difference from stock clearance?

[TTT]

did you get a "receipt" from the workshop for the RB rebuild?

as if you'd go on the word of the seller that it has a "built" engine

[GTS4WD]

Anyone know how much forgies expand once the engine is warm?

[Adriano]

Depends on the piston and the application, clearance for forgies can be anywhere from 2.5 to 5 thou.

[Beer Baron]

my advice is now that you know what brand the pistons are, contact the piston manufacturer and ask them wat PTB clearance they reccomend. it may in fact be 0.1mm (unlikely, but possible).

[Adriano]

my advice is now that you know what brand the pistons are, contact the piston manufacturer and ask them wat PTB clearance they reccomend. it may in fact be 0.1mm (unlikely, but possible).

I would guess .075

[GTS4WD]

my advice is now that you know what brand the pistons are, contact the piston manufacturer and ask them wat PTB clearance they reccomend. it may in fact be 0.1mm (unlikely, but possible).

YOU!

Your a thinker!

[GTS4WD]

**UPDATE**

I WAS looking for a piston to bore clearance of .035 - .05mm (as per Manufacturers requirements)

Called up some blokes down at Silverwater and .1mm seems too big..

So..

plan of attack..

Piston size of 85.95mm WILL fit a stock RB25DET bore and have a gap of .05mm (recommended gap) - Anyone interesed in a cheap set of forgies that will fit stock Rb25DET bore?

BUT

Because the mechanics at deadshit's mechanics R US bored the block out by .05mm (and hence increased the clearance to .1mm and therefore too big) the block and piston combination will not work.. - anyone looking at a cheap 25det block?

[Adriano]

I doubt it has been bored out 1 thou, 2 thou piston clearnace cant be right for the forgies, its just too small, they would sieze. 4 thou is only a little loose, why not just chuck it back together, it wouldnt have been causing the massive dramas that the car has.

[Cubes]

GTS4WD,

Try not to over complicate things.

Send the block in to be bored/honed WITH the set of pistons. The machinist will measure up the pistons and bore to suite your intended application. Obviously have a little discussion with regards to what the piston manufacturer recommends, intended use etc etc.

[GTS4WD]

GTS4WD,

Try not to over complicate things.

Send the block in to be bored/honed WITH the set of pistons. The machinist will measure up the pistons and bore to suite your intended application. Obviously have a little discussion with regards to what the piston manufacturer recommends, intended use etc etc.

Well im looking to put together a hi comp 25/30 NA project together.. so.. dont have much use for this..

But I may get the block sleeved and sell the whole bottom end off with the pistons..

Ill get a few quotes for getting it sleeved.. but I mean.. I seen a fair few 25DeT blocks going HEAPS cheap lately.. so Im not sure if its worth it.. but I will get back with you guys about it..

[proengines]

Those pistons will run .05mm or so clearance. They are not your usual forged piston which is forged from a billet, they are more along the lines of pressure cast. Being hypereutectic, the coefficient of thermal expansion is a lot lower than a piston forged from a lower silicone content alloy, so not so much difference in size from cold to hot. It would be a lot cheaper to buy a set of pistons than to have the block sleeved.