Wondering if anyone has had much to do with arias forgies with the rb30 and if so what piston/bore clearance are they running. They recommend .10/.004but have been told that this is a lil to much. Been told that the rings they supply arent the best either. Anybody had much to do with the pistons and or different ring combinations.

if they recommend 4 thou, run it. the CP's recommend 3.5 thou btw, what rings are they (material / widths etc) ?

i'd really like to find this out as well in the process of machine work and whats the .10 for? the .004 is the piston to bore clearnace

.10mm or .004" = same thing

if its goin to be making big power any thing between 4-5 thou is fine if its a street car with mild power i,d go 3.5 thou and are the rings they supplying you ductile ?

It depends which alloy the pistons are made from, Arias can, and do, supply either type. Pure aluminium race pistons are soft and expand hugely with heat, they MUST run big clearance to prevent seizure. They will rattle and wear out very quickly in a street engine. But they will take a hell of a pounding, and distort before they fracture. They are designed for SHORT LIFE race applications, and will wear out within a few months in a street engine. Hyper eutectic pistons are forged from exactly the same high silicon hard brittle alloy as stock cast pistons. They can run very tight clearance, seal well, and will last forever unless detonation kills them. They are strong only because they are thick and heavy, detonation will crack them easily. Forging is a manufacturing process not a material. Find out which material they are made from, and follow Arias's recommendation.

the only way you'll wear out a forged pistons quickyl is if you flog it before its warmed to operating temperature let it idle for a few minutes in the drive it will expand and seal better and prevent to an extent the rattle you speak of, yes the life will be shortened but i doubt very much so to a few months my problem is im running propane which means even more heat my problem is that who knows how much the piston will expand and what the recommended tolerances are based on, i opted for safety and ran 4.5 thou next is the ring gap

A few months is all you are going to get if you drive the car every day. Sure the engine will still run, but it will drink oil, and the blowby past the rings will be pretty high. But many guys could not care less about that. They usually blame the engine builder when the engine becomes smoky. There are two problems, pure aluminium is very soft, that is where the strength comes from, but it also wears fast. Every time you start up from cold, the pistons will rattle around and WEAR. All that rattling around means the rings have no chance of ever bedding in properly. Every heat cycle just adds just a little bit more to the problem, and stuffs the rings just a little bit more. Put it this way, which would work better in your car, rubber pistons, or glass pistons ? Rubber pistons for the top fuel dragster that only has to last one run, but take a hell of a beating during that one run. Glass pistons for the taxi, they are super hard will not wear, and will probably last forever. The rubber pistons would crap out third time around the block in a taxi, the glass pistons would shatter during launch in a dragster. Get the idea ? Some serious race parts are just totally unsuitable for a long life street engine. But many guys just cannot figure that out. If Joe Hero can run eights, they want to run exactly the same parts in their everyday road car. Get the high silicon forged pistons, they will last like factory pistons, they are just not as strong as the aluminium race pistons.

they will last for ages in a street car ive had many running for over 12 months now all on 4 thou bore clearence cause they where opting for decent power in the future but yeh im sure if i pulled them down now they will be out of shape but untill the rings give in theres no way to tell when i built nuggets that was making 360 @ the wheels and got driven pretty damm hard rev limiter dumps ect ect and it had no issues but as i said no way to see untill its pulled down to see how much they have warped

there is a difference between an 8 and a street car for example look at gas 747 paul runs arias and has so since i ever seen the car daily driven and still can run mid 10's all day it comes down to machine work and assembly, i will agree with a shorter life but not to the extent your speaking of

If u run a forged pistons made from 4032 alloy which will have around 10% silcon clearances can be run as low as 3 thou considering engine cooling is optimal. The 2168 forgings are a bugger of a piston mainly used for out right drag racing nitrous ect. They have a 1% silicon content and expand rapidly thus that the reason big clearances have to be implemented 5 thou ect. The 2168 forgings are obviously stonger considering their fairly soft but the 4032s will take a **** load more pinging/detenation the any cast piston.

Pulled the engine down, p/b clearance was 4 thou, engines done bout 7000kms now and skirt wear is normal, will be running same tolerance again, arias recommend 4 thou. ring wear was normal with no butting. Exhaust valves were coked up from poor tune and inlet valves not seating correctly. Be screwed together this week with new ecu and tuner to be used.

Quote: Originally Posted by DINGOVL Pulled the engine down, p/b clearance was 4 thou, engines done bout 7000kms now and skirt wear is normal, will be running same tolerance again, arias recommend 4 thou. ring wear was normal with no butting. Exhaust valves were coked up from poor tune and inlet valves not seating correctly. Be screwed together this week with new ecu and tuner to be used. what boost and fuel are you running there

will be running mobil 8000 for street with low boost, high boost will be around 25 with better fuel, not sure what fuel to go as yet maybe c16 or similar, also reading up on varying toluene mixtures as well. Still have testing to do before I run any high boost figure.

Do you cop any piston slap when the engine is hold with the 4 thou clearance i no most forged piston manufactures recommend 4thou

No engine noise at all when cold, always warm it up to temp before i drive anywhere and havnt had a prob with it. Hopefully get it together and tuned this week if not week after. No engine noise at all when cold, always warm it up to temp before i drive anywhere and havnt had a prob with it.

sounds good are u running the silcone based forgies or the 2168s

Quote: Originally Posted by vltrb-0 there is a difference between an 8 and a street car for example look at gas 747 paul runs arias and has so since i ever seen the car daily driven and still can run mid 10's all day it comes down to machine work and assembly, i will agree with a shorter life but not to the extent your speaking of paul's got SPS forged pistons..

whoops diff comp ratio too

Yeah it's all good. Just trying to raise people's awareness of some of the problems and pitfalls of selecting a suitable set of forged pistons. Most of the top piston manufacturers can supply pistons in at least two different alloys, for otherwise identical pistons. Just know exactly what you are getting, and choose something that will be best for your particular application (and expectations). These days a lot of street motors are being built with forged pistons, and much of what is supplied off the shelf is perfectly o/k for street applications. Just don't think that those pistons are the same as those forgies used in a national class winning competition drag race engine. The piston manufacturers know all this, but not all engine builders do. Or the engine builder might think it is a track car going to be trailered to the track at weekends only. Probably the worst people to buy pistons from are the part time counter sales people in the automotive parts shops. "Yeah mate got a set of forgies for an RB30 right here on the shelf ". He probably does, but what are they made out of ? and what is the recommended piston to bore clearance ? The rate of expansion decides the required bore clearance, and that will pretty much tell you how soft or brittle the pistons are going to be. Or put another way, what the silicon content of the aluminium alloy is.