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Rebuilding A Rb20

simor32

By simor32,
in Engines & Forced Induction

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simor32 Community Regular

simor32

Posted
Posted

he guys , latley ive been debating on wether to rebuild my rb20 or go the rb25 conversion. its been hard trying to find an rb25 with all the other things like gearboxes and turbos, all that shit. anywaz ive been told to rebuild the 20 and get the head flowed ect. ive got around 8 grand to play with and im in perth. wats the go with rebuilding rb20's . i want the car for the street daily driver and for abit of fun on the track aswell. any info of any kind would be appriciated

simon :)

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The Dan Grand Master

The Dan

Posted
Posted

stock bottom end is good for about 400hp but to be safe I would be changing to forged pistons. ROSS make custom pistons for the RB20DET and they will set you back around $1500 including rings.

I would definately consider the porting you mentioned as every little bit helps with the 20's. You should also have the rods resized to ensure correct fitment and lose the chances of spinning a bearing easily. 8 g's is not really going to satisfy the budget once you get right into it. You should do cams, injectors, AFM upgrades while you are at it and make sure you have a clutch that will do the job. The RB20 gearbox will not last long at 200rwkw so you should also budget for an RB25DET box and fit it at the same time.

R31Nismoid Grand Master

R31Nismoid

Posted
Posted

8k you have to play with?

RB25 conversion mate.

If you had a larger turbo etc etc already i'd say stick with the RB20.

But its pretty standard, so any cash you spend it going to better you regardless.

IMO Rebuilding the 20 and then doing a turbo will cost you more than an RB25 conversion, keeping the stock turbo and getting a PowerFC or similar.

RB20 box will be fine with a stock RB25 without a drama, even upto (give or take) 250rwkw in my expirience.

And that will be under 8k quite easily without having to do the gearbox. Which could even allow you to get a larger turbo for the RB25 + injectors/AFM 6-12 months down the track if you save a tad more :)

  • 2 weeks later...
Roy Grand Master

Roy

Posted
Posted

If you run good gearbox fluid, a sensible clutch and dont drive like you belong in a padded room then an RB20 box is fine up to 240-250rwks. It will go bang sooner or later, but my old thing is still tracking well after 180,000kms so its not unheard of. Some die straight after a power hike, so if it doesnt go in the first month or so you may be able to cheat death.

The big question is what are you wanting to do with the car and what can you so yourself?

8k is a lot of money. If your RB20 is happy at the moment, then i would grab a 2530, remapped ECU and be on your way for around $2500. Spend the rest of your money on big nights out and driving the car at the track with a good 210-220rwkws.

If you really want to spend the 8k, then its a lot of money if you can do things yourself, not a lot if your paying a workshop. You would be looking at around 3.5k for a mechanic to do the swap for you. You will need a Pfc and you will make around 200rwkws with a turbo that may go bag at any time.

So say 3.5k for work, 3k for engine and gearbox and driveshaft...it leaves you with a bit of money to play witha high flow turbo etc that will net you around 240rwkws.

RB25 is a good building block, but its a lot of money for that bit of extra low end grunt. RB20, well i wouldnt personally even crack the motor. Just throw a big turbo on it and go have a ball driving it. Be careful even with cams. I have ummed and arred so often with cams, but am concerned about losing even more grunt under 3,500rpm for that little bit of extra top end. I want cams more for the low to mid, and ppl have raised concern over me losing low end so havent bothered.

Which ever way you go, plan it well as you can, and get as many fixed price quotes as possible from ppl that have done it before and know what they are on about. You can do a turbo and ecu upgrade in 2 days. I can see an RB25 transplant taking 2 weeks.

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