Rb30/25 Vs Rb25/26 Build?

[Ohlsson]

Hi Guys!

At the moment I have an rb25 head and a rb25 block without internals. My plan was to build it up with rb26 crank and forged rods and forged pistons.

But I look more and more at rb30e bottoms. Is it a better choice to build an rb30 with forged internals and the rb25det head then to build a rb25det with 26 internals?

Is it possible with 8000-8500rpm with a rb30 with forged internals?

I will build for about 450Rwkw or 600rwhp.

[N1GTR]

RB25 VCT head then 30 bottom.

8500rpm no dramas for 3L bottom ends.

Everything you're asking has been covered to death

[Ohlsson]

Ok thank´s I have to count on how much it´s differs in price to build, If it´s about the sam price I will defenatly build a 30/25

[bubba]

If it's a RWD application then the only real cost difference is the $100 for an RB30E. The cost of everything else is pretty well the same whether you're building an RB25 or an RB30 bottom end.

It only gets more expensive if it's a 4WD application due to having to purchase a 4WD adapter plate.

[JonnoHR31]

few little costs such as welding the head, hose and fittings to T the oil breather into the turbo return, couple of drill bits and lots of swearing to do the vct feed. random little shit but its all pretty cheap when your doing a build anyway.

if your gonna do it try and get a 30e with lots of stuff still on it, a few little bits and pieces are needed, some are just handy and the rest can be sold off.

[dorifticon]

As noted above, if you are using an rb30e block in rear drive application you avoid some of the costlier fitment issues such as the sump adapter and welding and redrilling the rear of the alloy 4wd sump to mate to the bellhousing.

However there are other costs and pains (in addition to mating the head to the block). You will most likely need to run aftermarket oil and water feeds and/or drains to and from the turbo. That high-temp oil drain line and heat wrap isn't cheap.

You will need to sort out something about the power steering pump bracket. And depending on whether you are putting into an r32 or r33, this will dictate the level of modification required to get the hybrid 30 block to fit under the bonnet, which is not a trivial task.

Also remember the extra deck heigh moves all the hose/intercooler connections on the motor upward, so you need to factor in a way of adapting these to fit. Radiator hoses normally OK because they have sufficient flex but intercooler hoses etc can be a bit tricky.

All of this is achievable if you have a reasonably garage full of tools and are prepared to tackle problems as they arise but it all ends up being time and money.

[Simonster]

If you go 30 then you'll most likely need a clutch to handle the extra torque of the mighty 3litre

I highly recommend NPC's 800nm item, i have it in my3 litre and it's as light at factory- not bull

Edited March 23, 2011 by Simonster

[bubba]

As noted above, if you are using an rb30e block in rear drive application you avoid some of the costlier fitment issues such as the sump adapter and welding and redrilling the rear of the alloy 4wd sump to mate to the bellhousing.

However there are other costs and pains (in addition to mating the head to the block). You will most likely need to run aftermarket oil and water feeds and/or drains to and from the turbo. That high-temp oil drain line and heat wrap isn't cheap.

You will need to sort out something about the power steering pump bracket. And depending on whether you are putting into an r32 or r33, this will dictate the level of modification required to get the hybrid 30 block to fit under the bonnet, which is not a trivial task.

Also remember the extra deck heigh moves all the hose/intercooler connections on the motor upward, so you need to factor in a way of adapting these to fit. Radiator hoses normally OK because they have sufficient flex but intercooler hoses etc can be a bit tricky.

All of this is achievable if you have a reasonably garage full of tools and are prepared to tackle problems as they arise but it all ends up being time and money.

Definitely not insurmountable issues. I did my whole 30 conversion in a weekend, drive in, drive out.

Power steering pump bracket is easily fixed with a grinder, as with the exhaust manifold (or you can grind the block). Everything else bolted back up fine with a bit of massaging. I used an R32 RB25DE head which is more straight forward than the R33 RB25DET head. The only bit of turbo piping (stock 25 turbo) that was a bitch was the oil drain.

[ronnydotk]

As noted above, if you are using an rb30e block in rear drive application you avoid some of the costlier fitment issues such as the sump adapter and welding and redrilling the rear of the alloy 4wd sump to mate to the bellhousing.

However there are other costs and pains (in addition to mating the head to the block). You will most likely need to run aftermarket oil and water feeds and/or drains to and from the turbo. That high-temp oil drain line and heat wrap isn't cheap.

You will need to sort out something about the power steering pump bracket. And depending on whether you are putting into an r32 or r33, this will dictate the level of modification required to get the hybrid 30 block to fit under the bonnet, which is not a trivial task.

Also remember the extra deck heigh moves all the hose/intercooler connections on the motor upward, so you need to factor in a way of adapting these to fit. Radiator hoses normally OK because they have sufficient flex but intercooler hoses etc can be a bit tricky.

All of this is achievable if you have a reasonably garage full of tools and are prepared to tackle problems as they arise but it all ends up being time and money.

450rwkw, i don't think he'll be using to many of the stock pipes/manifolds on it. Most likely GReddy plenum, hi mount manifold with one of these. Even that turbo will be on its limits

[JonnoHR31]

However there are other costs and pains (in addition to mating the head to the block). You will most likely need to run aftermarket oil and water feeds and/or drains to and from the turbo. That high-temp oil drain line and heat wrap isn't cheap.

You will need to sort out something about the power steering pump bracket. And depending on whether you are putting into an r32 or r33, this will dictate the level of modification required to get the hybrid 30 block to fit under the bonnet, which is not a trivial task.

Also remember the extra deck heigh moves all the hose/intercooler connections on the motor upward, so you need to factor in a way of adapting these to fit. Radiator hoses normally OK because they have sufficient flex but intercooler hoses etc can be a bit tricky.

apart from oil drain as said (1 piece of hose needs to be made longer if it isnt long enough already) turbo lines bolt up exactly the same if you get a s2 block. $10-20 extra at most

p/s bracket takes 2 mins of modifying with a grinder or depending on which pump your using you can use the 30 bracket, which bolts straight up. $2 cutting disc if you dont have one already

in rwd applications you can redrill the engine mounts and drop it ~20mm, leaving the top of the motor only ~15mm higher than before, which wont cause any issues. $2 drillbit if you dont have one.

hardly super expensive

[bubba]

apart from oil drain as said (1 piece of hose needs to be made longer if it isnt long enough already) turbo lines bolt up exactly the same if you get a s2 block. $10-20 extra at most

p/s bracket takes 2 mins of modifying with a grinder or depending on which pump your using you can use the 30 bracket, which bolts straight up. $2 cutting disc if you dont have one already

in rwd applications you can redrill the engine mounts and drop it ~20mm, leaving the top of the motor only ~15mm higher than before, which wont cause any issues. $2 drillbit if you dont have one.

hardly super expensive

^^ this.

Srsly, I did it in a weekend. Helps having access to a workshop, a couple of engine stands and a mechanic mate with small hands