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High Comp Sohc Rb30


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I have a n/a rb30 in my gts2 and i dont wanna go turbo because its a svd car.

I have been doing some research but can't find any info at all on this subject, theres heaps on turbo conversions and rb25/26 head conversions but nothing on the sohc.

I know i would make more power converting to dohc but i'd rather keep the car as standard as possible.

I think the standard comp ratio is around 9 to 9.5:1 but would like around 10.5:1 or higher.

I dont know what a standard gts2 rb30 is meant to make atw's but i'd wanna get atleast 130 atw.

The only info i have found is that shaing the head would raise the comp slightly but would that be enough?

Any info much appreciated :blink: .

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u can get a cam thats one step higher than the GTS2 cams. from Camtech australia. they will suply u with a piggy back plug in ecu for the cam, get some head work done and u would easly crack 130atw.

i had a factory rb30e. got a stage 2 camtech cam which is almost the same as your GTS2 cam, extracors, full 2.5in zorst, decat, port and polish on the head and made 116rwkw. so u can easyly make 130 with the stage 3 cam.

email or call Camtech australia. and see how u go

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Ok thanks, will do. Maybe if i shave the head slightly to i can raise comp a little and with a bigger cam hopefully i will get some decent power. So with this piggy back will i be able to still run the svd one or would it replace it?

Has anyone tried rb25 pistons or different rods in a rb30 to raise comp?

Edited by eightsixboy
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Apparently rb25 pistons have the same bore size as the rb30 ones and have there gudgen pin sitting 1mm lower so that should raise the piston by 1mm giving you more comp, any know if this can be done? Or will you run into clearence issues with the valves? If clearence isnt an issue then combine that with a slight head shave then maybe a comp ratio of 10.5:1 or higher can be achieved?

Is there any workshops around vic that have experience with rb30's? I'm guessing I should try Nispro?

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  • 4 weeks later...

nispro are the bomb... their stg1 cam is your gts2 cam.. which is the biggest cam you can run without changing the ecu.

you could deck the head slightly... thats the easiest way and know one will ever know.. the gts2 heads are apparantly ported more than normal but there maybe a bit more that can be done or just general cleaning up..

xf throttle body to get more air in... or a twin standard set up.. and you could also make up some nice piping to increase the flow from the air filter if you havent done that already.. or GTR throttle bodies mated to the standard manifold.. but thats alot of work.

ive seen 300hp from a non cross flow 2.9L carby 6... with an injected RB30 head thats cross flow, there is no reason it cant make more power than you can use on the street... with an awesome sound..

cheers

Linton

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a mate of mine had a rb30e that was making well over 130kw at the wheels. i think the most he ever made from it was about 160kw. but generally it was around the 140 to 150kw range and wasn't the most reliable thing in the world (had a few rebuilds). he had it reving to around 8000rpm (or maybe it was 9000rpm, i can't remember). he had a twin throttle body setup, 3" exhaust, and all that crap. he was running low 14's in it, and i think they dropped the exhaust off one day he got down to about a 13.6 or 13.8. it was also a fuel guzzler. his father had helped build the motor for him. his dad and uncle had been using rb30's in speedway cars for quite a few years so knew lots about them. i think the only time a workshop touched it was to tune it, LOL.

i don't think he is on this forum, but i think he may have been on the r31 forum.

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mad082, do you know what his user name was?? good old r31 forum.. it was good fun

9000 rpm from an rb30 is pretty impressive... even if it was 8000rpm... thats fair reving.. do you know if it was still making power at those rpms?? or had it started to drop off??

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no don't know his username, and could find out a mod list. things i know off the top of my head are:

twin throttle body

3" exhaust

locked diff

lightened flywheel

button clutch

rb26 oil pump

(i think) 750cc injectors

then there was something about boring out the oil channels in the crank to allow greater oil flow.

and i'm pretty sure it made around 170kw with the exhaust dropped off at the cat. i was at a dyno comp on a hot day when it made just over 140kw., which was only about 15kw less than a vl turbo on 9psi that went on after it, LOL. but as i said, reliability was an issue, and he rebuilt it quite a few times. he used to take it to the drags all the time, and in burnout comps. certainly wasn't a daily driver (the fuel economy was really really really bad).

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I think your talking about the user RB30e? Dark blue over silver S2 silouette?

http://forum.r31skylineclub.com/index.php?topic=112677.0

Had some pretty hektic stuff done to it.

As for the OP question, you'll find you can buy aftermarket pistons for the RB30e that net it around 10:1 - you could then further on that by decking the block to the amount the headgasket compresses to, and then shave the head the last bit if that isnt enough for you. Then get a nice cam, and lots of lift (rb30's dont have enough, even with an aftermarket cam) get some adj rockers. Balance the bottom end, get decent intake and exhaust manfolds, and a good ecu and you could net similar results, you just need to sit down and think through it, get an intake manifold, exhaust manifold and cam that matches, then work the bottom end to match and flow the head to match. Get it done, have a laught, then the sooner you can get fed up with the cam lag, bad economy and hopeless drivability, to drop the high comp slugs and fit some VLT spec forgies @ 7.8:1 (the amount you shaved the deck etc should bring you to a normalish comp with these) and drop a GT35 on it and have an absolute animal :).

I love my N/A monster, but its not a street car, if you want heaps of streetable power, you need boost, otherwise to retain drivability you can only achieve moderate increases.

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I think your talking about the user RB30e? Dark blue over silver S2 silouette?

http://forum.r31skylineclub.com/index.php?topic=112677.0

Had some pretty hektic stuff done to it.

As for the OP question, you'll find you can buy aftermarket pistons for the RB30e that net it around 10:1 - you could then further on that by decking the block to the amount the headgasket compresses to, and then shave the head the last bit if that isnt enough for you. Then get a nice cam, and lots of lift (rb30's dont have enough, even with an aftermarket cam) get some adj rockers. Balance the bottom end, get decent intake and exhaust manfolds, and a good ecu and you could net similar results, you just need to sit down and think through it, get an intake manifold, exhaust manifold and cam that matches, then work the bottom end to match and flow the head to match. Get it done, have a laught, then the sooner you can get fed up with the cam lag, bad economy and hopeless drivability, to drop the high comp slugs and fit some VLT spec forgies @ 7.8:1 (the amount you shaved the deck etc should bring you to a normalish comp with these) and drop a GT35 on it and have an absolute animal :D.

I love my N/A monster, but its not a street car, if you want heaps of streetable power, you need boost, otherwise to retain drivability you can only achieve moderate increases.

i can't see the thread as i'm not a member. can you take a screen shot for me? but sounds like it. had stock shitty looking wheels.

actually i have a pic of him on a skid pan.....

burnout1c.jpg

burnout2o.jpg

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I have a n/a rb30 in my gts2 and i dont wanna go turbo because its a svd car.

I have been doing some research but can't find any info at all on this subject, theres heaps on turbo conversions and rb25/26 head conversions but nothing on the sohc.

I know i would make more power converting to dohc but i'd rather keep the car as standard as possible.

I think the standard comp ratio is around 9 to 9.5:1 but would like around 10.5:1 or higher.

I dont know what a standard gts2 rb30 is meant to make atw's but i'd wanna get atleast 130 atw.

The only info i have found is that shaing the head would raise the comp slightly but would that be enough?

Any info much appreciated :thumbsup: .

Pissing about with expensive, low gain mods will just hurt your wallet, and the resale as much as anything else.

Without a turbo, it will always be slow.

Nothing about NA RBs in general is conducive to good NA power, RB30Es are one of the worst of the lot. Heck, dollar for dollar an L28 will walk all over it.

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10.5:1 is doable for comp, I'm running over 12:1 at the moment (but I have a GT-R head siting on my block though) and it sings along quite nicely right through to 7200rpm (damn stock GT-R cams!) and I'm also using the RB25DE pistons.

Either way you'll have to get a re-map on the ECU or a full aftermarket item. Keep the GTS2 as standard as possible cause they are a nice looking car.

To get your goal of 130rwkw you'll probably need, re-tune, compression (should be able to get away with 11:1), lighter flywheel, some sort of balancing (rods, crank or whatever you choose to do), a clean up of the head just to get it neat and a good exhaust (decent extractors, good cat, 2.5" mandrel bent exhaust will do the trick and good mufflers). That should see around your goal power output.

The bloke you are talking about with the worked SOHC RB30, the current forum member that owns it is Nudge. The motor went into his white silo that he has. It only manged that quarter mile time (13.7 is the fastest recorded) due to the fact that the car had almost been completely stripped and it's current power output is 154rwkw.

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