RB25/30 - help please  

355DVL

no there is more to it than that it will bolt up but there is a hole needing to be drilled at the front of the head for the oil pressure sender if i remember correctly and a water jacket that needs to be blanked off

GTRVspec95

Moved to mechanical

180josh

What car is it going into?

im in the process now. . the standard things that you will need are a oil feed to the head for the VCT (if its a R33 head), also the oil gallery in the head needs to be welded. . (again if its an R33 head, if not, do not worry about the two things I just said). .

You will have to look into getting an aftermarket ECU unless you are using the stock RB25 ECU. Note: If you are using a R33 head you wont be able to use the R32 ECU as it does not have provision for the VCT. .

Also the compression ratio has to be taken into account. . If you are going for a turbo setup (using a N/A block and either turbo or non turbo head) you will end up with around 8.3:1 compression ratio. . most will argue that this is a bit low. . Try to aim for around 9:1

You should use the parts (sensors etc) corresponding to the head you are using, for example, if you are using the R33 head, use the R33 loom, afm etc etc. . makes life a lot easier. .

If it is going to be turbo I strongly suggest using a twin cam oil pump (RB25DET or RB26DETT) however, I do not think the RB26DETT pump will work with the crank without machining. . (stick with the 25 pump, I am)

If you are planning on revving it past 7000, I suggest getting the bottom end balanced and definitely using the twin cam oil pump.

Hope that helps a little bit. .

If you need more info pm me. .

mongrel_cae71

^^that's a very good list.
also add: move the idler tensioner to the area above the water pump(drill/tap into the block, seal the stud in place cos there's coolant behind it. the idea of this is to simulate the belt wrap you would get on a factory RB25 inlet cam gear.

and drill a small hole beside the idler and use a tensioner pulley there instead of the solid(Uses two tensioner pulleys: the second one allows you to adjust the length on the drive side so that you're cams are timed correctly/marks line up)

pipster11

need to get a specific length belt too as the 25 wont reache with the added block height and a 30 one its only single cam

or look here http://wiki.r31skylineclub.com/index.php?t..._Cam_conversion

09ONE

Decide on what oil pump you will be using before going much further.

You will need to use oil restrictors in the head and possibly external oil drain back to the sump depending on what pump/how much flow / max RPM.

Make sure you also get an aftermarket harmonic balancer. An RB30 one wasn't designed to cope with the higher revs and an RB25 one wasn't designed to be used on an engine with the stroke of an RB30.

ATI make a really good one, or Ross also dop a quality one for a good price.

You don't have to run the VCT either, it's no real drama to leave it or have it functional as an RB25 would.

180josh

I would recommend using the stock RB25 oil restrictors (part number is 11036 21U00)

Also, I am not too sure on the balancer. . Yes the RB30 block is said to have harmonic issues over and arount 7000, however, many people have run 7000-7500 all day long with a non balanced bottom end, stock balancer, and it is fine. .

Personally, I am using the RB25 balancer with a non balanced bottom end. . However this is only a mild build and in about a years time I am hoping to get the whole bottom end balanced with an aftermarket balancer. . Then you can say hello to the 8k range

09ONE

Seriously why?

It's not like balancing costs all that much espically if you just get the whole rotating assembly balanced rather then each individual part. It should be part of your machine work.

For the sake of $500-$600 the piece of mind is worth it. Then eventually when the engine does break you can take comfort in the fact that you did everything you could (although this kind of attitude is how my build got out of control...Engine still isn't in the car)

Why excatly do you want to do a mild build, only to do a full build later on? You end up doubling up on labour and machine costs and also parts costs like bearings, gaskets studs etc.

180josh

Well as it is I am only 18 and still on my p plates. . I have a 210RWKW RB30 in the shed with a fully forged and balanced bottom end. .

So as I see it now, ill just leave the bottom end how it is, as it is going to be NA, and then when I get my fulls, ill use the bottom end of my other motor along with turbo setup etc etc (GT 3540)

I am very tempted to get it balanced but just am not sure if it is worth it for the 2 years that I will have it. . I am also considering putting RB25DE pistons in to up the compression ratio, seeing as though I will not need this bottom end in my next build. .