Building A Forged Rb25

[XxNinjaxX]

hey guys ive reciently decided to build a new motor for my 33 as the original motor is quite tired and had a hard life due to previous owner abuse

anyway these are my plans which are subject to change but most are confirmed, im aiming for maximum torque and fast spool when i get my cams dialed in and motor tuned so all out hp isnt really what this build is about

os giken adjustible cam gears (possible hks)

gates timing belt

tomei poncams type-A (256 duration 8.5m lift)

autech forged rods

cp forged pistons (possibly a diffrent brand due to known failure)

N1 oil pump

N1 water pump

power fc

s15 470cc injectors

ported+polished head

ballanced bottom end

tomei rod bearings

tomei head studs (possible arp)

tomei main studs

now for the questions,

1.am i able to upgrade the valve springs to tomei type A springs and still retain the hydralic lifters?

2.whats the maximum hp i can make before a oil drive collar is required for the n1 pump? i understand that they have been known to fail more often than desired but the car is my daily and doesnt get driven excessivly ever really, just the odd squirt here and there but thats all, never will be rev'd above 4,000>5,000rpm max so should i be reasonably safe from failure without it?

3.what sort of power figure should i be expecting? depending on what turbo i choose, either way im going to run a max of 1bar to keep things nice and reliable

Edited November 4, 2010 by XxNinjaxX

[N1GTR]

Forget tomei bolts and bearings. Use ARP. It's the same part but cheaper.

If whatever crank you're using doesn't have the long drive, get a collar fitted. Do it regardless of hp you'll be using. You've got a heap of expensive and unrequired stuff (like bolts, stock will do cause your injectors limit you to ~470hp) but you want to skip a very small cost part like the collar? Get the collar.

If this is e85 you'll need bigger injectors. Got a good fuel pump?

CP pistons are fine, and cheap from the states right now. You could probably get better rods, I remember seeing some great rods at a decent price from USA last week, can't remember where though sorry

You can't ask for a power figure at 1bar without saying what turbo, and even then depending on the rest of the setup people would just be guessing.

I don't see the point in not revving past 5k, if you won't do it get an rb30 in there....or a v8

[R31Nismoid]

Just use GTR rod's. Its what mine had put into it, was fine.

470cc injectors limit you to just over 300rwkw anyway.

If you are keeping boost to 1bar, honestly, no point even building the motor. To make 300rwkw on 14psi you'd need a huge laggy turbo which makes it pointless

[redevil]

Mate, not being silly but I agree with the above people. It sort of seems like you've googled engine rebuilds and just copied a list.

Like I'm not poking fun but you state your not going to use it for any major performance purpose but aregoing down the avenue of cams, cam gears etc.... You list some expensive brands like Tomei when ARP is the tried and tested brand and also cheaper.

You have rods, pistons etc... but have made no mention of an upgraded crank.

What sort of fuel system are you running??

What sort of computer / tuning controls are you running??

what supporting mods will you be running, (intercooler, exhaust, coils, etc...)????

If you only want it as a daily and not chasing any major figures why waste the money on cams etc.. when all you need is if anything a standard rebuild...

As I said I'm not having a go but you list pistons then state your not confident in them. What are you trying to acheive then people will be able to help you with what you need to do.

[Harey]

Agree with redevil, I dont even know where to start.

Maybe go back to what your aim is from this. If you want to freshen up your engine with a rebliable increase in power. I would get a standard rebuild and choose a turbo to make 250-280rwkw. Heaps of info on this site about the turbo options.

If you are not going to rev it over 4-5,000rpm why build an engine?? Why even own a skyline??

[Nee-san]

Agree with redevil, I dont even know where to start.

Maybe go back to what your aim is from this. If you want to freshen up your engine with a rebliable increase in power. I would get a standard rebuild and choose a turbo to make 250-280rwkw. Heaps of info on this site about the turbo options.

If you are not going to rev it over 4-5,000rpm why build an engine?? Why even own a skyline??

As above, buy a V8 if you only want to rev to 5,000RPM.

[redevil]

If all you want is a daily driver that you can run a bar of boost through than stock the engine is capable of it. If you feel the engine is worn then don't waste your money on the above list. Some new seals and gaskets, maybe rings and your set.

Port and Polish - Waste of time unless your chasing big power and running high boost and in that case what you would want is your engine to be bench flowed to match intake plenum and exhaust manifold. (bare in mind this is not a small job and not a basic mod, it is for as I said big power)

[Harey]

Yup and choose a really responsive turbo like a HKS GTRS so that you can enjoy as much boost as possible under 5,000rpm.

[XxNinjaxX]

my aim of this build is top produce a motor for my daily that is awesomely reliable but still produces a nice power and torque figure, my aim is anywhere from 300>350hp atw safely and without having to worry about the motor breaking while im giving it a bit of stick on the odd occasion, as i said my main aim is a large torque result as its the torque that you feel while getting putting your foot down not the hp so i want to get the absolute highest (yet safe) midrange torque result from the motor. not intrested in high end power as you cant use it on the street therefore no point aiming for it as its just my daily.

all help is welcome just dont flame me remember i am only new at this so dont explode if i say the odd stupid thing..

Edited November 5, 2010 by XxNinjaxX

[jangles]

RB30 for torque

[zebra]

Just buy a good condition stocker, or throw some new rings and bearings and crank collar in the current engine....no need for forged rods/arp bolts etc if its just a street engine, so unless you plan on doing some serious endurance circuit work there is zero need for half the stuff in your list.

and sif v8's only goto 5000 lol, mine will goto 6500rpm and live for years

[battery]

yeh your underestimating the reliability of an untouched rb25.

200000kms with a decent tune and regular servicing is almost expected!

[iseekool]

@ the OP.

What mod's are currently on your car?

Get a compression test of your engine to help see how tired your engine is - and judge from there if you need the bottom end touched at all.

[Just for reference I have an original 1983 L20b powered Bluebird that has done 250,000+ km and still has an even 160psi across all cylinders]

- Get a standard rebuild and head clean.

Reliability mods:

- External oil cooler.

- Larger radiator and termo fans.

- New stock water pump (N1 if you want to spend)

- New stock oil pump (N1 if you want to spend)

- Bigger fuel pump and injectors

Performance mods:

- HKS GTRS turbo

- Nistune

- Stock GT-R FMIC

- Exhaust

[zebra]

thermo fans are the gay, leave the factory fan imo

[iseekool]

thermo fans are the gay, leave the factory fan imo

I'm curious - why are thermo fans bad?

[NickR33]

run GTR rods with ARP bolts... balance the lot... any of the top piston manufacturers will be fine, its all in the build

forget the cams, head work etc... leave the head alone

get a decent bolt-ons instead... good FMIC, Nismo 550cc injectors etc... don't forget fuel pump, Nismo or Tomei in tank

leave standard radiator (just flush it)

Nismo coppermix clutch, Bilstein or Tein suspension (no China crap)

and get a really good tune from someone who tunes 25's

[zebra]

Factory fan with shroud will pull more air than any thermo setup I have seen

[NickR33]

factory clutch fan does a great job, no need to change

thermos never seem to work as well unless they are shrouded properly etc

edit: beaten to it;)

[r33cruiser]

run GTR rods with ARP bolts... balance the lot... any of the top piston manufacturers will be fine, its all in the build

forget the cams, head work etc... leave the head alone

get a decent bolt-ons instead... good FMIC, Nismo 550cc injectors etc... don't forget fuel pump, Nismo or Tomei in tank

leave standard radiator (just flush it)

Nismo coppermix clutch, Bilstein or Tein suspension (no China crap)

and get a really good tune from someone who tunes 25's

Oh I dont know mate. I made 350hp at 12psi with a 5000rpm limit.

Where as on old engine with same turbo etc without headwork/cams, i made that at 16psi at 8000rpm.

If you have the money, you will see the gains

[Supa Steve]

Forget tomei bolts and bearings. Use ARP. It's the same part but cheaper.

If whatever crank you're using doesn't have the long drive, get a collar fitted. Do it regardless of hp you'll be using. You've got a heap of expensive and unrequired stuff (like bolts, stock will do cause your injectors limit you to ~470hp) but you want to skip a very small cost part like the collar? Get the collar.

If this is e85 you'll need bigger injectors. Got a good fuel pump?

CP pistons are fine, and cheap from the states right now. You could probably get better rods, I remember seeing some great rods at a decent price from USA last week, can't remember where though sorry

You can't ask for a power figure at 1bar without saying what turbo, and even then depending on the rest of the setup people would just be guessing.

I don't see the point in not revving past 5k, if you won't do it get an rb30 in there....or a v8

Tomei is the same part as ARP? Who's leg are you trying to pull now?

You have a habit of pretending to know what you are talking about but in reality you have no idea. Leave the expert comments to the guys who actually have the expertise. Tomei run a widened step in the shank and use 6 point nuts where ARP run a parallel shank and use 12 point nuts. They also do not share common base material and are formed using different manufacturing process.

Edited November 5, 2010 by Supa Steve