How many KM'S have you done on forged pistons?

[Amaru]

From what I was told my Arias pistons are a 2 thou over bore. They were ordered from Rocket Industries with the following details;

AP331177 ARIAS NISSAN SKYLINE GTR TURBO FORGED-20 OVER

Im getting a mixed response from mine. Sometimes she starts fine, sometimes its a real hassle to get it to start. Ive been told until the rings seal and bed properly (considering ive only done 600km since the engine was rebuilt - its in today getting head retensioned and throwing away that dirty run in oil for Mobil 1) this would be a problem. It seems to be getting better as the km's get higher and the rings bed I guess, and it only struggles to start maybe 1 out of 5 times now as opposed to 4 out of 5 times.

[Amaru]

Ok well the problems starting are not caused by the pistons. Workshop narrowed it down to leaky injectors, so will have those replaced in the new year and should all be good On a side note, the car is running like a dream now it doesnt have that bullshit run in oil in it

[RNS11Z]

3000kms with wiseco forgies. No piston slap. No cold start noises. Smooth and still kicking hard.

[Warpspeed]

Yes Joel, it was a 250 Ford motor de-stroked to 221. It had 7:1 Arias blower pistons, Crower rods, cross-flow head, and a T04 V trim turbo with E flow turbine and 1.0 a/r running 20 psi. The seven thou clearance was what Arias recommended for the bore size (at that time). A brand new block, ultrasonically tested, was bored and honed oversize especially to suit the pistons. This thing had billet steel bearing caps and a steel flywheel with Falcon GT twin plate clutch. The head was fully ported with oversize valves and roller rockers. It ran no head gasket, but had dykes gas filled sealing rings around the bores, and a smear of silicone seal around the water passages. Chrome molly studs were used for head and main caps.

I still have the motor actually out in the shed. I could never sell it.

It might sound pretty barbaric these days, but in the mid 70's it was a fairly radical motor. Three were built at the same time. One went into a racing hydroplane, one into a sports sedan, but this one was strictly for street. It cost me about twenty grand all up for the motor, when the car itself cost me only three grand brand new off the showroom floor.

I had ring sealing problems, and also rapid valve train wear from the radical cam and massive double Crower valve springs. I learned a few things from it though. One was never to be so bloody stupid ever again.

When I read about people doing radical things to GTR engines, I just sigh, and think yeah, one day you too will regret all the money wasted on youthful folly. But is was fun though.

[Cubes]

I see why you have a bad taste in your mouth.

I had a few friends when I was growing up with the TD/TC cortina's. One had the TC with the 2V pre-crossflow from a fairlane. Went pretty damn well stock with a holly and a set of extractors. It ran a 14.9 1/4.

The mate with the TD had a crossflow that had a mild cam, holly and exhaust. He was lucky enough that the car already had a chopped down 8" LSD.

The stock Pre-crossflow 2v used to flog it suprisingly. He then ripped out the motor and did porting, bigger valves, big cam that rev'd to approx 6,000rpm. Obviously the cam was way to wild and the engine only lasted 15,000km's. Went well though.

But yer. This is my last stint with wasting money on cars.

[Bl4cK32]

But yer. This is my last stint with wasting money on cars.

Sure u didn't say that when u had the vs joel?

[Warpspeed]

Oh, you can still have a lot of fun with cars, but as Clint Eastwood says "A man should know his limitations".

I have built lots of motors myself, before and since that expensive little adventure. Yes it was a TC Cortina, nine inch diff, four wheel discs. It even had a Hone planetary two speed overdrive on the diff ! I still have that out in the shed as well.

A lot can be done with mostly stock parts, and assembling it yourself, a bit of head work and some cams. The rest is all bolt on externals with a turbo. So it need not be horribly expensive.

It is when you get a professional engine builder to start X raying this, shot peening that, special crankshafts and rods, custom pistons, big dollar head work. It all adds up and is probably a total waste of money in a street car.

Over the last ten years my priorities have shifted. I now am a total tight arse with cars, and have become more interested in finance and investing. I have yet to reach my first million, but am almost there. That is why I do not have a Skyline yet !

I used to spend every cent I had on cars, but not these days.

[Sydneykid]

Hi guys, I though this was a thread on forged psitons, not the philosophy of spending money, although it is an interesting thread of its own.

We have a set of JE forged pistons in an engine that is now 5 years old and has done 117,000 klms. Did a rings, seals, gaskets, bore and hone rebuild at 80,000 klms. Pistons looked almost brand new. They will outlast the rest of the car by at least 5 years I reckon.

My experience has been that properly machined and balanced forged pistons will outlast cast pisitons by a generation or two.

Hope that helps

Merry Xmas to all

[Cubes]

Sure u didn't say that when u had the vs joel?

erm no...

They were repair bills..

Within 6-9months off the top of my head I spent 5k in driveline/chassis repairs due to the car not handling the power/driving style that well.

Skyline handled it for the last 2 years with no breakages. That says something to me.

[Warpspeed]

Hey Sydneykid, sorry for straying off topic.

What sort of clearances do modern forged pistons run ? I am really interested in this.

[the phantom]

I've recently purchased a set of Arias pistons for another RB30DET in the pipeline. The pistons were provided by Rocket Industries specifically for this conversion. The compression is supposedly in the order of 8.5:1 but measurement will tell.

The spec sheet provided with the pistons states a clearance of 4 thou. Interestingly however, it also states that if the pistons are "PRO-COATED" the clearance can be reduced to 2 thou. I've only breifly investigated what "Pro-Coating" is as far as Arias is concerned. There was a "Pro-Coating" service provided by a NZ company but I'm not sure if this is the same treatment. Regardless it appears to be a typical dry moly type coating. However I fail to see how this would stop piston expansion due to heat. Perhaps the Arias treatment also includes a ceramic coating on the piston crown which would probably reduce the amount of heat entering the piston and hence limit expansion. I think some consultation with Arias is in order.

OEM clearance specs for the RB25/26 from the JPNZ R33 manual are :

RB25DE/DET 0.5 - 1.4 thou (approx)

RB26DETT 1.4 - 2.2 thou (approx)

Of interest is the fact that if the Arias pistons are indeed "Pro-Coated" the clearance falls within the OEM RB26 spec.

[Warpspeed]

Thanks for that Phantom.

[Warpspeed]

There is an interesting forged piston thread on another Forum here:

http://www.eng-tips.com/gviewthread.cfm/le...id/71/qid/58034

[Sydneykid]

Hi guys, when you guy a set of forged pistons the manufacturer supplies a data sheet with them which specifies the bore clearance, amongst others. The amount of clearance is also relevant to the bore diameter ie; an RB20DET piston will have different clearances to an RB26 piston from the same manufacturer.

[Warpspeed]

Yes, you usually get a standard printed sheet that gives recommended bore clearance in thou for each inch of bore diameter, and all sorts of other useful information. Can anyone quote figures for different brands of forged pistons ?