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Cheapskate Rb30det Questions

too_much_boost
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too_much_boost Mentor

too_much_boost

Posted
Posted

Hi Guys

I've got a Series 1 Stagea that i'm looking to give a bit more power. They are a heavy car so I'm looking for more torque. I figure that an RB30 bottom end is the best way about this.

Mine isn't AWD anymore. It has an R33 motor and RWD auto box in it. The auto is shiftkitted but otherwise standard. This will limit my power output requirements to around 250rwkw as I don't want to rebuild the box.

The stuff I already have sitting in the garage are:

S2 rb25det with low comp in one cylinder (overboosted). Head should be ok

3076r 0.63 IW or GCG highflow

480cc injectors

Z32 afm

step 1 hks cams + adj exh gear

The plan for ECU is nistuned Z32

The car already has fmic and 3in turbo-back

My questions are:

1. Which is the best RB30 block to use? Are R31 skyline blocks ok? Or should I only be looking for VL blocks?

2. I read that the combination of an R33 RB25DET head with the RB30E bottom end will give me an 8.3:1 CR. Will the extra capacity make up for the loss in CR from 9:1? Remembering I want to utilise the head/cams/cam gear I already have at home

3. Which parts will I need to use from each engine to complete the package?

4. What other cheapskate suggestions do people have?

Thanks

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TiTAN Grand Master

TiTAN

Posted
Posted

most of this info is in the RB30 sticky.

1. Series 2 VL block.

2. the extra capacity makes a massive difference to how it drives.

3. every thing from the current engine but substitute the RB30 bottom end instead of the 25 from your current engine with a couple of small modifications everything bolts on. (though its recommended to replace the water and oil pumps while its apart)

4. use a stock RB26 1mm head gasket to maximise compression.

also use the 3076 over the high flow, you will probably find the high flow runs out of legs around 5000rpm.

too_much_boost Mentor

too_much_boost

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Posted

Thanks for the replies. I have had a skim through the sticky but it is 170+ pages!

Extra queries relating to your answers:

1. So the S2 VL block is best. What difference is there between this block and an R31 skyline block?

2. What I meant here was will the RB30 with 8.3:1 be better down low than the RB25 with 9:1? Is it worth the hassle of using the non-VCT NA RB25 head to get the higher CR, but lose VCT? If i use the non-vct head, then i can't use my hks cams i assume

3. OK cool. Since its cheapskate, i probably won't fork out for an oil pump but will do the water pump

4. if the rb26 HG is 1mm, how thick are the stock ones (RB30)?

TiTAN Grand Master

TiTAN

Posted
Posted

1. check the PDF in the first post of the RB30 sticky. it has that info.

2. as i said it is a massive difference between the 25 and 30 down low the saying "theres no replacement for displacement" rings true. Both the R32 NON VCT head and the R33 VCT head should give the same compression. that being said the R32 head is a simple bolt on the R33 head needs some modifications for the VCT to function and to stop oil/water mixing.

4. The stock RB30 is probably 1mm also but RB26 stock gaskets are easy to source as production wasn't stopped nearly 20 years ago.

femno Grand Master

femno

Posted
Posted

Yeah I was going to suggest the same thing.

I know you want to be a cheapskate, but if youre going to all this trouble you might as well make it go fast...

Having said that please do the oil pump instead of the water pump! It is WAY more crucial to the engines survival, not to mention its piss easy to change the water pump later if you have to.

too_much_boost Mentor

too_much_boost

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I was going to use the oil pump off the broken RB25 I have in the garage.

This isn't going to ever be seeing a racetrack or be pushed hard. I'm really just thinking the RB25 isn't quite enough to lug around the stagea's lard arse. This car probably will be used for car towing duties before long

Duncan Grand Master

Duncan

Posted
Posted

exactly the same reason I put an rb30 in my stagea....check out my thread in the stagea section

btw i kept an undersize turbo because i love the instant response. obviously it runs out of puff at the top end, and also it doesnt help fuel economy :O

but it makes me smile every time I floor it and I have full boost by 2500

too_much_boost Mentor

too_much_boost

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Posted

I don't think this is going to be any sort of rush job. The RB25 is still running, so I'll just keep my eyes open for a decent rb30. I don't want to go forgies or anything so I'll just look for one with lowish kms and maybe replace rings/bearings.. or perhaps chuck it in as-is.

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