Used Forged Pistons, Pics - Can I Used Them, Bore Questions

[Adriano]

But the cylinders arent nitrided from the factory, and the surface hardness gets machined off in the initial bore by the factory.

[deant1]

i'm not sure about the nitriding.

Any boring of the cast block would be simply a fraction of a milimetre to ensure the tolerances are spot on. no where near enough to weaken the wall of the cast.

[monga]

Rb blocks can be bored to 87 mm without any issues, of course you would only go to 86.5 mm if the block is 86 mm now .

Sleeving will make it much stronger but its very costly..

There is no way I would re-use these pistons if I was to do a re-build

Even if the pistons were perfect you would have to re-use them in that block , don't forget Nissan pistons are graded so they are different sizes even in stock virgin engines .

I've had my rb26 block sleeved ands its crack pushing around 500rwhp~~

[wrxhoon]

I've had my rb26 block sleeved ands its crack pushing around 500rwhp~~

I have seen plenty RB 26 blocks cracked , this is why N1 blocks( 24U) have thicker bore jackets and Nismo GT blocks (RRR) thicker again ...

[r33_racer]

last time i checked when pretty well anyone rebuilds a motor with oversize pistons which is normally only 20 thou oversize or .5mm thats generally all that gets taken off unless the bore has ovaled so much it needs more then 20 thou. I seriously doubt anyone goes sleeves for first oversize piston when rebuilding. You said it as if its required for rebuilding, which it isnt.

[proengines]

The standard bore isn't nitrided. There is no problem boring RB's oversize, I did one late last year to 88mm and it's been making over 700rwhp without any problems. Even at 88mm you only reduce the thickness of the cylinder walls by 1mm. I wouldn't sleeve one unless you had a valid reason to, a split bore or the like.

As for the pistons, if they are still on size and not cracked there shouldn't be a problem reusing them. Have a good look at the pin bores as they might have some galling due to the lack of oil supply. If the pin bores are damaged, throw them away. otherwise, clean up the skirts with scotchbrite and make sure there is nothing foreign embedded in them. Also, fit some new rings. I wouldn't do it on a customers engine but for your own it is not a problem if the parts are ok.

Weigh up the cost though, sometimes a new set won't cost a whole lot more by the time you pay someone to measure and crack test them, buy new rings and circlips etc. Rings for many of the forged pistons about can cost over $300 a set with proper steel top rings etc.

[cosworth1971]

Do people realize if there really forged pistons there worth 500-800$ dollars and very strong <not something you throw away easy unless your super rich

I would re-use if they have been checked out properly.pics are too hard to tell?

[STATUS]

Not sure which part of my post you want me to explain more, but:

Cast iron (cast anything infact) - soft on the inside and hard on the outside. depending on the size of the cast but generally speaking you don't want to bore out a cast block because at least you are making the hard walls thinner.

Nitriding - the cyclinder surface is hardened using nitriding, expensive to get the cylinders re-nitrided. and it is a key reason why the cylinders are so durable in RB engines.

Cast iron and nitriding = very hard and durable surface. depending on the amount of material removed from the walls ( if you get them bored) would decide on how much you degrade this surface.

The practicle way of getting past this is simply boring to a size that allows you to insert cylinder sleeves which come ready hardened!

hope i answered any of the q's you had,

EDIT: i thought the cylinders were nitrided also, but if i'm wrong it doesn't really matter because sleeving is used to combat the problems of boring in to cast. same outcome.

that is the most shite ive ever heard... i been building engines for ages and youve got your shit alll mixed up maybe youve been playing with nicasil and so forth in 2 strokes but your conventional 4 stroke is happy to go 20, 40 and in some cases 60 thou.... (60 thou ives used a bit on high hp 253 engines)

[GeeTR]

Not sure which part of my post you want me to explain more, but:

Cast iron (cast anything infact) - soft on the inside and hard on the outside. depending on the size of the cast but generally speaking you don't want to bore out a cast block because at least you are making the hard walls thinner.

Nitriding - the cyclinder surface is hardened using nitriding, expensive to get the cylinders re-nitrided. and it is a key reason why the cylinders are so durable in RB engines.

Cast iron and nitriding = very hard and durable surface. depending on the amount of material removed from the walls ( if you get them bored) would decide on how much you degrade this surface.

The practicle way of getting past this is simply boring to a size that allows you to insert cylinder sleeves which come ready hardened!

hope i answered any of the q's you had,

EDIT: i thought the cylinders were nitrided also, but if i'm wrong it doesn't really matter because sleeving is used to combat the problems of boring in to cast. same outcome.

The crack must have been from a good year ? 

You cant bore out a cast block? Sleeves don’t just slot into the cylinders, and then how are all the mating surfaces decked? The whole block has a LOT of work done to it between being cast and assembled.

Iv never heard of someone nitriding the type of iron that a RB block is made from.

I'm not sure how one sleeves a sleeve either. Oh gosh, im more confused then ever! hehehe

Mafia - is this your R33 with W/M Injection? If so, how sad. RIP

M

[The Mafia]

lol no, Just letting everyone know that this WASN'T my engine, but an engine that I bought from someone that blow theirs. I got it cheap, and the HEad is in excellent condition (ported etc)