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RB30 or rebuild rb24

quincy777

By quincy777,
in Engines & Forced Induction

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quincy777 Community Regular

quincy777

Posted
Posted

Hi all, firstly dont want this to become a bitchy battle!!

My car is r32 4door (rb20) with following mods, apexi FMIC, Apexi Power FC, HKS oil cooler and relocation kit, full turbo back exhaust, cold air induction and pod, r33 turbo (s2), full HKS suspesion, clutch, diff, front and back struts, floor brace etc etc, you have the idea. Its a great car and planning to keep for next 10 years, yes 10 years! but car is already tied from hard life in japan and now from me on track. It is also my daily drive

I have done heaps of research over the last year and know the pros and cons of both just want experience to make the best call for the long term plan. Due to funds doubt I will have enough to get a turbo so rb25 will have to do for now. but want car to run reliable 250rwkw (with a new turbo im guessing)

1. rb30 bottom with rb25 head.

2. rebuild rb20 to rb24 and do some extensive head work including rb25 valves if they fit.

Both will have forged bottom ends. and want to use my power fc (r32)

I guess it comes down to this, if you were spending this sort of money with a 10 year out look will one end up being more reliable, cheaper, enjoyable than the other.

cheers

Cam

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pitchd Proficient

pitchd

Posted
Posted

i am in the exact same boat...

sorry to semi-hijack...

but i have a 32 4 door... which is getting a fresh rb20 with 1.2mm headgasket, power fc, hks t04e external gate kit, hks twin plate, rb25 gbox, trust front mount and z32 etc etc fitted...

i know the rb20 wont take the t04e for very long - especially considering its going to be drifted...

i was thinking of purchasing an rb20 short motor (block/head) so i can strip it down and get it rebuilt/stroked with forgies etc... question is... im unsure as to what has to be done and used...

which crank would i use? rods?

- adz

Bl4cK32 Grand Master

Bl4cK32

Posted
Posted
i am in the exact same boat...

which crank would i use? rods?

- adz

Rb25 crank and rods make it a 2.3Lt

rb26 crank and rods make it a 2.4Lt

I think this was what i found when i was looking at the same options....

P.S. a short motor is just the block, a long motor is the head and block together...

Sydneykid Grand Master

Sydneykid

Posted
Posted

When I added it up for myself (and several others since) the RB30DET was cheaper for the same power output. For example a completely standard RB30 bottom end will get you 280 rwkw. I built one that has been going strong for nearly 5 years now at that power level and it cost less than $1200 for the bottom end, rebuilt and balanced with new seals, gaskets, rings and bearings. You can't do an RB20/23/24 with that much power for twice that much. Plus it will have to run higher boost and rev to higher rpm which will shorten its life.

Easiest decision ever, I went for the RB31DET and I already had the RB20 block, RB20 cylinder head, RB26 crank, RB26 rods and 4AGZE pistons :D

quincy777 Community Regular

quincy777

Posted
  • Author
Posted

Easiest decision ever, I went for the RB31DET and I already had the RB20 block, RB20 cylinder head, RB26 crank, RB26 rods and 4AGZE pistons :D

Cool no wories, makes sence. So do you rebuild with forgies for that price.. Is it best to by a rb30 in good condition and not rebuild it or buy on price with expectation of wanting/needing to give it some attention. Where is the best place to get rb30 bottom end from.

Sydneykid Grand Master

Sydneykid

Posted
Posted
Cool no wories, makes sence.  So do you rebuild with forgies for that price..  Is it best to by a rb30 in good condition and not rebuild it or buy on price with expectation of wanting/needing to give it some attention.  Where is the best place to get rb30 bottom end from.

No forgies, it was a STANDARD bottom end, that means standard RB30E pistons.

Any Holden wrecker will have an RB30 or 2 in stock, just don't mention "Skyline" they will double the price. Says it is for an "old VL" or something. Pick the closest one to you as they weigh 100 kgs or so and you don't want them freighted around, they get dropped. I would always rebuild an RB30, they are 19 years old after all. :D

Scooby Veteran

Scooby

Posted
Posted
When I added it up for myself (and several others since) the RB30DET was cheaper for the same power output.  For example a completely standard RB30 bottom end will get you 280 rwkw.  I built one that has been going strong for nearly 5 years now at that power level and it cost less than $1200 for the bottom end, rebuilt and balanced with new seals, gaskets, rings and bearings.  

Exactly what I thought possible and what I want to do albeit with RB26 bits (even experimented with a quote from GEM for $1600 assembled, extra for balancing and anything else I want ).

SK I assume you buttoned it up yourself at that price? Would forged pistons allow you to stretch to a safe 350 rwkw or so? What rpm limit do you observe? Did you ceramic coat the pistons to overcome the absence of oil squirters?

Regards

Sydneykid Grand Master

Sydneykid

Posted
Posted
Exactly what I thought possible and what I want to do albeit with RB26 bits (even experimented with a quote from GEM for $1600 assembled, extra for balancing and anything else I want ).

SK I assume you buttoned it up yourself at that price? Would forged pistons allow you to stretch to a safe 350 rwkw or so? What rpm limit do you observe? Did you ceramic coat the pistons to overcome the absence of oil squirters?

Regards

Yes, I assembled it myself. The problem with a standard RB30E is everything (except the crank and block) has a ~475 bhp limit. So replacing pistons alone does very little for increasing the safe power limit. You need conrods, head studs, main bearing studs, decent bearings, oil pump etc etc So I either have a 475 bhp RB30 or a 750 bhp capable RB31, anything in between costs me the same anyway.

We have added block mounted oil squirters (it's a bitch of a job) and ceramic coated the pistons with conrod oil squirters. Both methods seem to work equally well at the power levels we run. Cost wise, go the ceramic coated piston crowns and conrod based oil squirters.

Hope that makes sense:cheers:

Scooby Veteran

Scooby

Posted
Posted
The problem with a standard  RB30E is everything (except the crank and block) has a ~475 bhp limit.  So replacing pistons alone does very little for increasing the safe power limit.  You need conrods, head studs, main bearing studs, decent bearings, oil pump etc etc  So I either have a 475 bhp RB30 or a 750 bhp capable RB31, anything in between costs me the same anyway.

Both methods seem to work equally well at the power levels we run.  Cost wise, go the ceramic coated piston crowns and conrod based oil squirters.

Thanks SK,

Is that 475hp x .75 = 350kw at the fly? Allowing for losses atw that would equate to the 280 rwkw you mentioned.

Your comment that 'anything over 475 hp costs the same' makes sense. But assuming the $ for a bullet proof engine aren't available and if a stock RB26 can make 280rwkw safely, why go to an RB26/30 except for a bit more torque (and a fair bit more messing about to install it). Is it the cost? What am I missing?

What rpm limit do you observe for the stocker bottom end?

Regards

88silhouette Grand Master

88silhouette

Posted
Posted

massive fan of rb30s

whacked rb25 head on my rb30 bottom end in my 4door oz 31

30detdyno.jpg

i was always impressed with the torque of the rb30e. but the twin cam combo has me pissing my pants. it's frickin brilliant. tdo6-20g. front mount all the usual shit. usual rb25 afm. crappy plum back bov. not running well at the moment. whacking in q45 afm. better plum back bov. boost controller (provided thew 2door below sells sometime soon) then will try and give it a squirt on the dyno tuner @ 15psi

at the moment, runs on 8psi and squeezed out 226 at the rears.

rb30 all the way mate

Scooby Veteran

Scooby

Posted
Posted
massive fan of rb30s

whacked rb25 head on my rb30 bottom end in my 4door oz 31

30detdyno.jpg

i was always impressed with the torque of the rb30e. but the twin cam combo has me pissing my pants. it's frickin brilliant. tdo6-20g. front mount all the usual shit. usual rb25 afm. crappy plum back bov. not running well at the moment. whacking in q45 afm. better plum back bov. boost controller (provided thew 2door below sells sometime soon) then will try and give it a squirt on the dyno tuner @ 15psi

at the moment, runs on 8psi and squeezed out 226 at the rears.  

rb30 all the way mate

thanks 88, picture tells a thousand words. 226 ATW on 8 psi is excellent. stock bottom end?

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