RB25DET buildup (got my clip). Internals issue

[1_revin_Silvia]

I just received my RB25det clip from Flashoptions. I'm planning on building it up. I'm going for between 500 and 600 hp. I've been reading some on the internals of this engine and also what other people are doing. Naturally I have a few issues. I just want to make sure it's all done right.

I'm planning on picking up some forged pistons, ARP studs and head bolts, new connecting rods, beefing up the valve springs, complete gasket set with a 1.2mm head gasket. That sums it up for internals and makes it ready for some good mods to get me to where I want to go. The stock bottom end is good for at least 600hp, and the crank is good for at least 650hp. Correct me if I'm wrong

Do you guys think I'm covering everything to make my goals for power safe? Also, someone suggested port and polishing my head and hone intake manifold. I'm somewhat familiar with these terms but not enough I think. Could someone enlighten me on what they mean and what benefits come from them?

-Thanks
-Justin

[1_revin_Silvia]

Ok I wasnt very clear on my plans with the port polishing thing. As far as that goes Im extrude honing my head, intake and exhaust manifold, and port matching them to the head. If this sounds right then let me know.

-Justin

[khfromhb]

that all sounds good, but have your crank balanced and blueprinted just to be safe

[2rismo]

I think this is an awesome project, mate. But seriously, you couldn't get an RB26DETT motor for similar money?

Adrian

[HellBent]

Justin,

I don't know too much about the RB motors, but I can tell you that airflow is a tricky business. Just extrude honing the intake and heads may increase your HP a little but not in the way that will build the best gains.

I won't bore you too much, but what it comes down to is airflow and energy loss. As your piston moves downward on the intake stroke it is creating a low pressure area in the cylinder that wants to be filled by the higher pressure of the atmosphere. The problem is your intake track, and all it's obstructions stand in the way and rob energy (pressure) from the incoming air. The filter, throttle bodies, turbos, tubing roughness, bends, valves, etc... all take their associated energy loss. Reducing those losses is key.

Turbos obviously add energy back, but the losses are what you are trying to overcome. Assuming you have bigger throttle bodies, and a low restriction air filter, the intake and heads are your next area for improvement.

Wider or bigger intake runners, with large hogged out heads, and big valves with high lift sound great, but are only a peice of the puzzle. The intake, heads, valves, and cam need to be matched to the turbos and exhaust, not to mention the fuel system. Go too big or too small realative to other parts and you are wasting money.

A good speed shop or a lot of online help may steer you in the right direction. I would say that extrude honing the intake, combined with a simple port job of the heads, a great valve job, accurate port matching shouldn't be too expensive and will go a long way towards consistent power.

Before you get crazy with bigger valves, cams, turbos, or nitrous, you really need professional advice from someone who knows RB engines inside an out. Beware of simple solutions... there are none when it comes to running high HP! Unless of course you have a deep wallet and don't mind learning expensive lessons.

Good luck,

-AL

[RazorGTR]

When you say stock bottom end is good for 600hp they really are not. Not on the RB25 block, even trying to get that reliably out of the RB26 is a HUGE ask.
The cranks are good for 650 easy but I wouldn't suggest trying to push more without an aftermarket one. JE forged pistons will do the trick and they are cheap compared to the Japanese ones. Good thinking with the ARP rod bolts!

As far as the head work, the standard head with standard cams are quite good, however I wouldn't suggest running over 8,200rpms as you will get valve bounce. If you go to slightly heavier springs it will help just don't go nutso as you will destroy your cams. Trust make a good set of street cams where aftermarket springs are not required. If you plan on a port-n-polish not much needs to be removed maybe a good tidy up for the power levels you are looking for. A GTR style intake plenum is a good start and so is a good exhaust mainfold.

I wouldn't personally go with a 1.2mm head gasket, as a 1.1 or even a 1.0 would be sufficient, just a good metal one .

You will need some decent injectors of around the 650cc range though 720's would be perfect for your application. See if you can get your hot little hands an on a Q45 single throttle body! Unless you plan on running a MAP ecu also a Z32 AFM will be needed as they have a wider reading band.

Remember you can have all the right bits but at the end of the day the tuner will make or break you project.

Best of luck.

[1_revin_Silvia]

Wow guys, I wasnt expecting that much help and feedback, but it's appreciated immensely. You've all been a great help. I'm going to revise my engine buildup and in due time, I'll repost my updated plans for the buildup and see where I stand then. Again thanks for the help people, and I look forward to posting my car's progress over the next year or so.

-Justin

[SubaruImprezaYM]

How do you guys know so much do you research online or are you guys actually mechanics because i am still in high school and planning in getting into auto mechanics. What is the highest paying auto mechanics, enginnering...etc job which will give me the chance to work with high performance cars.