Forged internals

[Minorci]

Have a question relating to engine rebuilds... Currently my rb20 is getting the whole thing done, and im about 90% certain installing forged pistons, what i want to know is, because money is an issue i can only afford forged pistons, not getting the rods shot peened etc... Is it still a worthwhile mod?

Just a little bit of background... Live up in darwin, average temp of 32 degrees, 18-24 at night. I'll be running 12-14psi through it, with a garret gt28 rated at 400hp with a microtech ecu. FMIC etc...

[nv033]

as far as i know 'high revs = rod breakage'...im not quite sure what the rb20 rods are rated at and to what limits u are willing to push them.... a good investment from my point of view to shotpeen, linish, a rehole the holes (excuse the terminololgy) an investment of around $70 per rod with upgraded arp rod bolts may be worth stretching ur budget....comparing aprox $400 vs anywhere starting from $1500 for aftermarket rods is food for thought.... ive noticed alot of big cars built by the reuptable workshops in sydney just prep the rods in this manner eg. rb30 and rb26...both pushing 400rwkw + .... not saying rb20 will reach this but i would back it to see up to 300rwkw think it comes down to the good old question what aplication do u have in mine....shot peen etc do strengthen the rods to what extent ... speak to ppl with experience will be the best bet good luck!

[Lepperfish]

If you wanna take your car further with mods later, do the rods aswell now, if you only want to run that 400hp turbo, get the rods crack tested and as nv033 said, get them reholed for the ARP rod bolts..

[Steve]

Forged pistons have excellent heat dispertion qualities, which in your case especially, will assit in keeping detonation at bay.

Having said that, the best way to prevent detonation is to get a good tune and drive sensibly. If you are only running 12-14psi, it could be debatable whether or not you 'need' forged pistons.

The RB20 already has an 8.5:1 CR stock, if you are not increasing the CR with the rebuild, wont be running over 12-14lbs, have a good tune, good FMIC, good fuel supply and dont thrash the car after it has been sitting idling getting a heat soaked cooler (perhaps even fit a cooler spray?) - it should be fine.

RB20s will easily handle the power you are aiming at, and do quite nicely even with a redline around 8000rpm.

My personal choice would be spend the money on a decent head port and tune:) RB20s are pretty cheap nowadays - theres even a guy selling a rebuilt one for $800 in the FS section.

[Roy]

The Gibson Motorpsort R31 GTSR reportedly used standard RB20 crank and rods. Is thats true then the std rods must be decent enough things as that engine had in the realms of 450hp (flywheel), had a healthy redline (something like 8,500rpm) and ran healthy amounts of boost, definitely over 12-14psi you are thinking of running.... though the rods would have been prepped

[Bobjones]

The standard rods are reasonably decent, the RB25 ones are forged, the weaknesses lie within the fact that the foging process is not complete. I would recommend getting the rods, crack tested and shot peened, which basically cleans up the rod as uneven or weak points cause the breakage at high RPM and with detonation.

I would also recommend all new bearings and ARP bolts are almost a must with forged pistons as this helps keep things together considering you are building the engine to take more punishment. That does not mean you skimp on the tune which is vitally important...

Also make sure your engine builder bores the chamber as specified on the piston spec sheet along with the correct honing as specified on the ring set. All to often rings do not bed in properly as honing is not done properly resulting in stripping the block down AGAIN...

[predator]

The standard rods are reasonably decent, the RB25 ones are forged, the weaknesses lie within the fact that the foging process is not complete. I would recommend getting the rods, crack tested and shot peened, which basically cleans up the rod as uneven or weak points cause the breakage at high RPM and with detonation.

Like he said I keep reading its not the actual design of the nissan rods as they are quite strong, but simply the small imperfections in there. As most will know a tiny crack or tear can turn into a large one under stress in any material. Higher HP, and/or detonation is going to do that. Shot peening, or blasting the surface with tiny beads or "shots" clears and smooths the surface, hopefully reducing any cracks or imperfections and the probability i guess of them spreading, and then failing. Hence I guess giving a higher tollerance for error in the rest of the engine.

If you can't afford the rest not sure whether it really makes too much sense just adding forged pistons on their own... as it seems like you'd be taking other shortcuts there too to save costs?

[Minorci]

Hrmm apparently Aria, and Wyseco dont make pistons for rb20's....is this correct or not? Can someone please suggest where i may find some... besides the TOMEI forged pistons.