450rwhp doable on stock bottom end and stock head

[leesredgt]

ok i was wondering is 450 wheel horsepower doable with the stock block and head besides cams and bigger turbo and all the other goodies thay come with tuning the engine i was figuring that to get that much wheel horsepower you would need right at 540 engine horsepower.so any advice would be much appreciated.

[rb25drag]

Ya it is do-able with Stock block, but not stock pistons, Which your not going to find any aftermarket pistons less than .020 oversized. Stock rods will handle it and the head as long as you get ARP head studs and a good head gasket.

I would focus alot on balancing the assembley. It will save your bearings, Create alot less stress on the internals during high RPM runs, and give you an awesome rev, Believe it or not it will allow not as much lag on turbo spool up too due to the motor revving more freely!! But a good machined motor is a happy motor.

[JPsNissans]

Are we talking about the RB25 here?

You can do 450whp stock internals on an RB25... I believe I've seen almost 600whp stock internals IIRC. Just gotta make sure you have a really good tune and all your supporting mods are up to the task.

[leesredgt]

yes were talkin about a rb25det, i guess what i am asking is on stock everything as far as bottom end b/c if its not then ill get the tomei 2.8 liter stroker kit but if it can be done with a good tune then i wont worry about spending the extra 5,000.

[midnightsliding]

vision performance has a 450hp stock RB25, and they have a stock RB25det street car making over 700hppic of their 700 HP stock RB25.

[USMCgetsome]

NICE ENGINE p0rn!

[Cjmartz2k]

I made 400rwhp before, and I haven't dyno'd it with the new turbine, but it's easily 450rwhp camparing it to before with the old butt dyno. Stock everything (including head gasket) at 1.5 bar

[leesredgt]

so were saying 600-700hp doable/thats like rb26 territory/2jz territory.

[Fearsome_tea]

The 25 block has more webbing then the 26. And yes you can have 550 hp with completely stock bottom end, head, cams, and head gasket. I know a guy that make close to 500hp with a stock intake mani and throttle body. And so far as the life of the engine that will depend on the tune. My car has over 100,000 miles and and I make over 500hp.

[Darius]

Ya it is do-able with Stock block, but not stock pistons, Which your not going to find any aftermarket pistons less than .020 oversized. Stock rods will handle it and the head as long as you get ARP head studs and a good head gasket.

I would focus alot on balancing the assembley. It will save your bearings, Create alot less stress on the internals during high RPM runs, and give you an awesome rev, Believe it or not it will allow not as much lag on turbo spool up too due to the motor revving more freely!! But a good machined motor is a happy motor.

Not trying to be a d!ck, but there is some misinformation here.

1) There are aftermarket forged pistons that are the stock bore size. I have some..I don't know where this notion came from??

2) The head does not need modification nor does the head gasket. The reason most of the head gaskets blow is because the head bolts stretch and the cylinder pressure blows the gasket out. A metal head gasket is added insurance, but if you don't have to crack open the head, DON'T!

3) By nature, the I6 motor is one that balances itself and, therefore, does not need a lot of effort to get it to balance properly. As long as the crank is balanced and the pistons+rods are within a gram of eachother, your bearings are not going to notice a difference. You are correct in saying that balancing is important but it is not a huge issue with the I6. Maybe on a V-oriented motor or I4.

4) And I don't see how a balance job is going to make the engine rev more freely to spool the turbo?? Maybe if your balancing included significantly lightening the rotating mass (i.e. flywheel, pistons, rods)

I think the part that is the limiting factor is the piston. You can add all the strength upgrades you want, but the pistons are bound to blow apart above 500 hp. The rings and ring lands are just too big of p****** to take the abuse. With a good tune, they will last longer, but its only a matter of when they will fail. Either be satisfied with a lower power level or you are looking at a total rebuild where you might as well replace the pistons, rods, cams, head gasket, ALL internal fasteners, etc. I hope you have deep pockets for this

[rb25drag]

(Darius) I looked for STD bore pistons when I blew one of mine. I could not find them anywere, Everyone only had oversized pistons! Thats why I said they dont make them b/c I was unable to find them. That was a year ago.

Second: To balance an I6 is not as hard as a v6 but it is very critical, You are correct as long as everything is within a gram, The problem is when I built my motor I used top of the line parts but when I put the pistons,Rods on the scales they were from 6-30 grams within each other! My machine shop said it was due to the types of materials they used.

But point being if you just throw any combination together its more than likely going to be off a little. It is just added insurance to take the extra step and have a safe motor built cause I know I would NOT tear back into this motor a second time.

Balancing is like bearings with no grease, If you balance you give the bearings some grease and allow it to move more freely! If you don't you cause it to stress just a hair more than it should have to, Under a huge load of strain is were you will tell the difference!

The Pistons are the weakest link in these motors. I would not feel safe at all with 450HP on stock pistons. Just my opinion tho,

[Darius]

I got my standard bore CP pistons from compulsivehp. Jim is great to work with.

Initially, I was just looking for upgraded rings a few years ago and wow was that difficult. Finally decided to screw that idea and do it right the first time.

I agree that balancing is important mostly for piece of mind that you did it right and other issues you may be having later on down the road will not be because you screwed around on the bottom end.

[leesredgt]

okay so how much hp can the tomei 2.8 liter kit handle?with there being stock size pistons out there is this somthing i can do my self as far as upgradeing the pistons and rings or should i still have a shop do it?

[Darius]

If you're gonna go that direction, I don't think the 2.8L kit uses stock bores. The bores should always be honed when installing new rings so they seat properly and wear in correctly. Assuming you rebuild the entire engine with the kit installation, you could easily have 700 hp. If you wanted to push it, I think 900 hp isn't that far out of reach. For only 450whp, you don't even need that kit. It is wayyyy overkill.

Extremely high power levels require extensive modification of oiling/cooling/fuel system and you'll run into major costs. Just ask kjlindgr. I'm sure he's got about $30k in his build, but he'll be pushing 1000hp for sure.

[Coolwhip]

sock Rb's, hahaha

[leesredgt]

okay say i wanted to push 600bhp(not that im gonna just trying out all my options)would i have to touch the crankshaft and if so what crank would i need as far as using the stock pistin size but with everything redone. the only reason i cosider doing the tomei kit is there crank is like 2000 dollars so i figure why not pay the extra 2 grand and get the rods pistons and rings?

[Darius]

The crank is never the weak link in these motors or any motor for that matter. Engineers design other cheaper parts to fail before the crank is even stressed. You can run a stock crank and get 600hp, but you WILL need to replace the pistons. IF you had an RB26, I'd say run it as is since the top ring and ring lands are considerably stronger.

But since you want 600 hp out of on RB25, you have crossed the bolt-on upgrade level and entered the engine rebuild level.

You're kind of in a gray zone for power so if you dropped your goal to 400 whp, you wouldn't necessarily need to rebuild anything. Conversely, it will be necessary to rebuild if your hp goal exceeds 450whp.

[leesredgt]

ok,well that tells me were i stand,looks like for now my goal is 425whp for now.i think thats a good start

[until240]

not to thread jack, but...as stated earlier in the thread, i have read that the ring lands are the weak part of the rb25, and go out around 500hp. So the question i have is if i get cp pistons, will my ring lands be able to handle more hp without busting?

[Coolwhip]

I believe its rated for 200hp per cylinder so subtract your 15% drivetrainless what have you and there you go.

So CP's will do the job.

However, its all about the tune! You can destroy forged pistons on a 250whp setup with a wack tune.

[Darius]

ya might want to research what a ring land is before you even think about touching your motor.

[Coolwhip]

AH! I hope you know I was talking about the CP pistons are rated for 200hp each not the stockers.

and Darius is right.

[Darius]

Here are a couple pics of the stock RB25DET and RB26DETT pistons and rods. Notice the thicker rods of the RB26 at the base end and the noticeably thicker top ring on the piston vs the pewny RB25 ring. You can also see a slight difference in ring land thickness on the RB26 as well. The second rings and oil rings identical though.

The 26 has cooling channels in the pistons and the RB25 does not and the wrist pins are the same diameter but the RB26's are longer and thinner on the ends.

[until240]

awesome. thanks a lot...and as i'm sure you've noticed, i'm not going to be doing the rebuild myself...it's already at the shop!

[JPsNissans]

Thanks for that Darius. The pictures are worth a thousand words. I never knew how much bigger the RB26 rods are, holy crap.

Looks like that RB25 had a little bit of a ring problem
Modified by JPsNissans at 4:31 PM 11/30/2007

[PSI240SX]

all you guys are talking about this power being achievable on stock bottom ends.... Does a stock oil pump, no collar count? I want to make 400 or so, wondering if I can get away without modifying the crank/oil pump. No one has addressed this here so I was just curious. Also if this collar and new oil pump is needed, can they be installed without pulling the motor out? Like up on a lift?

[Cameron]

I heard the oil pumps can be a PITA to replace sometimes, like i heard, that sometimes they dont go on there right or something, and you have to weld them on sometimes.. im not messing with my stock factory one its not leaking, so im just gunna weigh out whether or not i wanna replace it.. is that information right or wrong? i heard it from a local dude..

[Coolwhip]

Incorrect cameron. Actually the oil pump isn't bad at all to replace. Given you engine is wedged in your engine bay your gonna be in tight spaces. No welding of any sort on the oil pump is needed, or recommended.

The collar can only be fixed/installed with the engine out, and pretty much torn down to its bare bones. Crank needs to come out. There you have the open of either having a set screw hold your collar or having it welded.

The collar issue is from high revving. It begins to round off the oil pump drive on the crank. But that's not your only problem. You'll also want to adress the over flooding of the head in hi revs (thus the fix is the drain back head mod). Same with the oil feed galleriew must be addressed with restrictors.

And so on

[Cjmartz2k]

Is that only on 26's, or all RB's?

[Coolwhip]

All RB's are plaqued with the oiling issue. However, the later model rb26's and the rb25 neo has the crank collar fix from factory.