Fix Thread turned into Re-build thread! (built rb25 neo)

Post by **mott6904** » Mon Feb 01, 2010 4:29 pm

There is a guy selling a set of rb25 pistons in the rb classified section. You chould ask him to measure the distance between the pin and the top of the piston. maybe a rb25 piston will work .

Post by **Darius** » Tue Feb 02, 2010 4:07 am

The RB25 piston has a lower wrist pin height so it would push the top of the piston further out of the bore at TDC when used with the same rod as the RB26 piston.

I want to re-address my previous statement regarding the possibility of changing the crank to an RB25. If the stroke is 2mm different between the two cranks, then half of that would be at TDC and the other half would be at BDC. SO, I need to correct myself in saying that it would drop the piston at TDC "2mm". It would really drop it 1mm.

If the pistons are currently at 0.5mm above the deck, the crank drops them 1.0mm and have a 1.0mm gasket: The squish clearance would be 1.5mm which is nearly stock. As long as the squish is within 2mm, it should still work as designed. Any larger and you'll get higher knock potential as Cjmart2k explained.

I just wanted to clarify this before you dropped $1200 on custom pistons.

Post by **Cjmartz2k** » Tue Feb 02, 2010 4:53 am

Hmm, I didn't think about using an RB25 crank as a cheap way out. If that math does work out, that's a good solution. John, that block I mentioned has a neo crank sitting in it too. It's a short snout though before you ask. The BS the aussie's spread around about the neo's having fixed oil pump drives is just that--BS. Later model RB26 cranks are the ONLY cranks that ever came with the extended drive collar.

Post by **Darius** » Tue Feb 02, 2010 5:06 am

Cjmartz2k wrote:Hmm, I didn't think about using an RB25 crank as a cheap way out. If that math does work out, that's a good solution.

I hope that works out, but I still have concerns that the significantly smaller combustion chamber of the NEO will still keep the compression above reasonable levels.

Also, good to know about the crank snout. The nice thing nowadays is that the adapter collars are floating all over the states. I remember when we had to order from Japan, it cost 2X what they cost now, and we had to wait 2-3 weeks for parts to show up. Ahhh the good ole days.

Post by **Coolwhip** » Tue Feb 02, 2010 6:51 am

Darius wrote:The nice thing nowadays is that the adapter collars are floating all over the states. I remember when we had to order from Japan, it cost 2X what they cost now, and we had to wait 2-3 weeks for parts to show up. Ahhh the good ole days.

Don't remind me

But hey, if needing a replacement NEO short block, let me know, will have something available this weekend.

Post by **sickness14** » Tue Feb 02, 2010 8:00 am

The rb26 piston still has a huge dome compared to the oem neo piston. If I use cjmartz crank I think ill still have an issue, dome still above block

Are we positive the neo crank is the same stroke as a regular 25?

Coolwhip (ricky) send me a quote for the neo shortblock... [email protected] this may be what ill have to do. Id still need pistons if I got the crank and block from cjmartz.

Then ill need to weld on collar to use my n1 pump on that new crank.

s*** this is going to be a pita.

Then I could part my current block out. Ill miss the bored and stroked setup gahh

Post by **Darius** » Tue Feb 02, 2010 8:16 am

Since the bore of the RB25 NEO is 86mm just like the S1/S2, the stroke must be the same. Therefore, same crank dimensions.

I have CP pistons and the dome sticks up above the block by ~5mm. You should be able to tell the internal clearances just by holding the cylinder up to the head surface to see if it clears. Valve relief is another part of the picture, but you should be able to verify that as well. At least hold off on buying a new short-block until you can verify that an RB25 crank will not work to correct the issue with your current piston/rod combo.

You don't need to weld the collar on. It is press fit and then drilled and secured by set screws. Any machine shop can do it without a problem. I don't recommend welding on a crankshaft unless you plan to machine it.

Post by **sickness14** » Tue Feb 02, 2010 3:55 pm

OK guys, ive been thinking and this is what ive come up with. Please give me feedback

Option 1 I can get a fully assembled NEO short block and i'd leave it completely stock and bolt my head up and be done with it, probably make a max of 500whp or so before any concern and then i'd have to just sell my complete bottom end i have.

Option 2 keep my fully built bottom end and sell the neo head to get a basic rb25 head (theres ways around the power FC tuning expecting the variable timing which wont be there). The basic head will provide the correct compression ratio at exactly 9.11:1 if i bolt it on (at least thats what the compression ratio calculator says)

So guys, it's either replace the head, or replace the bottom end

either built head , or built bottom end. I'd lose my cams if i got another head, that head is where the power comes from. its got solid lifters, (higher revs), bigger valves, NCVS.

On the other hand, keeping the bottom, the block would be bored and stroked with GTR internals, so its like a mack daddy R34 GTR bottom.its such a tough call. and it would cost about the same either way i think.

It's much easier to swap/build a head later on down the road than it is to do a built block, cause you'd have to pull the whole motor again

A fully done up RB25 head vs. a fully done up RB25 Neo head... How much of a gain are we talking about?believe it or not i think the regular head has more aftermarket options but comes less equipped stock. Though It'll be hard to sell the neo head. once your block is in the car, it's in. and it's already done

Im just trying to see what benefits me more power wise. I really only want 500whp or less out of this thing for a LONG time. I think i should be straight keeping my neo head & cams, and parting with the bottom. after all, the block has been decked like three times, and its the ONLY part of this whole build remaining from the previous owner, and we all know how well it was put together then

now this is all theoretical, based on the dependency of my pistons (which are above deck at TDC) working with a series II rb25 head. since nobody's proven to me that a neo head / GTR bottom end has been done before.

Post by **S14-NEO** » Wed Feb 03, 2010 7:25 am

take it from me , i kept my NEO internals completely stock and ran great for a good while. but i skipped one step that i should have covered before i threw it in the car. i should have installed ARP rod bolts in there and becuase i didnt my car has been sitting dormant for the past 6 months or better due to a stretched rod bolt..

Post by **noodl35** » Wed Feb 03, 2010 7:56 am

If you are spending all this money. Why haven't you considered a rb30 block? I've seen some for sale recently. That would be badass, just my thoughts....

Post by **S14-NEO** » Wed Feb 03, 2010 2:42 pm

HEY!!!!!!!!!!!....i'm the only one doing the NEO RB30 setup here in the US...i dont want no company just yet...lol

Post by **noodl35** » Wed Feb 03, 2010 3:24 pm

S14-NEO wrote:HEY!!!!!!!!!!!....i'm the only one doing the NEO RB30 setup here in the US...i dont want no company just yet...lol

LOL, c'mon man, give this guy a break here! Trust me, he deserves it...especially the obstacles this dude has been through. Besides, the rb30 is the block he needs in my opinion. From what I've seen and read, no one has regrets going rb30...

Post by **sickness14** » Wed Feb 03, 2010 8:19 pm

S14-NEO wrote:take it from me , i kept my NEO internals completely stock and ran great for a good while. but i skipped one step that i should have covered before i threw it in the car. i should have installed ARP rod bolts in there and becuase i didnt my car has been sitting dormant for the past 6 months or better due to a stretched rod bolt..

Good call. I can swap over the head studs, rod bolts, N1 oil pump, new water pump, all timing pully's and etc, and also the oil pan bc it has the sump return AN fitting welded on. Anything else im missing? OH yeah and hopefully the new bottom end will have a crank pully attached thats in good condition. mines chipped as seen in above pic. i really dont want to spend 600 on a damper right now.

would you suggest even replacing the bearings? i mean ive got a brand new set of standard main & rod bearings for the rb26 but i recall the 25 using the same bearings b/c the rods are the same, and main bearings work on either block. i just dont know if its worth the headache if its in good shape. i should just leave well enough alone at this point.

so ill get this new bottom end, and also have injectors lined up at the moment for a good price, 880cc precisions bnib with rb26 resistor pack.

then i just need that exedy twin disc pull type from ricky.

-J

noodl35 wrote:
LOL, c'mon man, give this guy a break here! Trust me, he deserves it...especially the obstacles this dude has been through. Besides, the rb30 is the block he needs in my opinion. From what I've seen and read, no one has regrets going rb30...

lol thx guys. im sticking to the stuff in the books from now on. no hybrids for me anymore haha. next motor maybe... lol. s*** ill have enough parts left over! haha. anyone need anything by the way? ive got it all listed in the FS section of the RB forum (classifieds)

Post by **S14-NEO** » Wed Feb 03, 2010 9:51 pm

honestly , if the bearings are in good shape i would just leave them be..just make sure you have the area clean and sanitary and dont get the journals contaminated with dirt in any way ( which im sure you knew that without me telling you that ).

Post by **sickness14** » Thu Feb 04, 2010 5:04 am

S14-NEO wrote:honestly , if the bearings are in good shape i would just leave them be..just make sure you have the area clean and sanitary and dont get the journals contaminated with dirt in any way ( which im sure you knew that without me telling you that ).

Good call. think its worth the trouble to swap the ARP main bolts too?

Post by **S14-NEO** » Thu Feb 04, 2010 6:40 am

if your in there and youved got them i dont see why not man

Post by **neonbomb** » Thu Feb 04, 2010 7:21 am

This is Bumbleetunas old car right?

Glad to see you're still at it OP!

Post by **sickness14** » Thu Feb 04, 2010 7:23 am

neonbomb wrote:This is Bumbleetunas old car right?

Glad to see you're still at it OP!

haha yeah bro. hardly though... when i get this new block, it'll be a completely new motor setup. i've been through hell and back with this thing. could have built 2 of these cars with the money i've spent :p lol or bought a supra...

Glad to hear from another Neo owner. Dude we gotta meet up some time when i get mine running. RB Road trip ftw.

Post by **Coolwhip** » Thu Feb 04, 2010 7:45 am

how about a RBJDMWTFBBQ? I'll host it if I get my nico rb peeps to show

Post by **sickness14** » Thu Feb 04, 2010 8:17 am

Coolwhip wrote:how about a RBJDMWTFBBQ? I'll host it if I get my nico rb peeps to show

Im down. I'll bring the

1. Coolwhip2. sickness143. 4.

haha jk would be cool though.

Post by **Cjmartz2k** » Thu Feb 04, 2010 3:04 pm

sickness14 wrote:
Im down. I'll bring the

1. Coolwhip2. sickness143. Cjmartz2k4.

haha jk would be cool though.

I'm in. Where we going?

Post by **sickness14** » Thu Feb 04, 2010 4:02 pm

Cjmartz2k wrote:
I'm in. Where we going?

hmm. this could actually work. well, id at least have to have my car running so it could be several months from now but we could do a meet somewhere on the east coast since thats where the majority of us live. except those midwestern RB guys. I'd have to think about it. somewhere cool. i like city settings but not sure where. florida would be bad a**, and a cool drive from NC.

-J

Post by **S14-NEO** » Thu Feb 04, 2010 5:53 pm

plenty of RB powered S chassis's here in the sunshine state...hopefully whenever this thing goes down (if it goes down) my car will be up and running with a replacement NEO engine in it .

Post by **sickness14** » Thu Feb 04, 2010 9:38 pm

S14-NEO wrote:plenty of RB powered S chassis's here in the sunshine state...hopefully whenever this thing goes down (if it goes down) my car will be up and running with a replacement NEO engine in it .

I'm right there with you brother.

Post by **Coolwhip** » Fri Feb 05, 2010 10:16 am

sunshine state +1, BBQ weather 12 months year (minus 1 week out of the calendar).

I know for the midwest guys, StricNyne is planning for a Vegas trip sometime this year. So we can also have a meet there too!

I'll figure it out

Post by **l0nestar** » Sat Feb 06, 2010 3:22 am

Hmm.. JDMWTFBBQ? interesting.. It may be a drive for me though. lol.

Post by **mott6904** » Sat Feb 06, 2010 5:03 pm

I need a vacation bad. I havnt been out of indy in a long time.

Post by **boosted98gst** » Sun Feb 07, 2010 2:29 am

You indy guys need to meet up with some of us ohio guys this summer! or vise versa!

Post by **mott6904** » Sun Feb 07, 2010 8:36 am

Thats cool with me I wont have a car done by then, but ill have a couple bikes to pick from to play with you guys. Another forum im on always get some good racing going in the summers. when we arrange something ill let you know the details.

Post by **sickness14** » Wed Feb 10, 2010 8:23 am

UPDATE

-Precision 880cc Top feed, high imp. Injectors are on their way thanks to the RB classifieds section. -Sourced a new SII rb25 head complete, port & polished with oem cams. waiting for response from user. -trading my AEM tru-boost for a Greddy Profec E-01 tomorrow (the one with the screen, F&F style yo)

the end.-John

Fix Thread turned into Re-build thread! (built rb25 neo)

Re: (sickness14)

Re: (mott6904)

Re: (Darius)

Re: (Cjmartz2k)

Re: (Darius)

Re: (Coolwhip)

Re: (sickness14)

Re: (Darius)

Re: (sickness14)

Re: (S14-NEO)

Re: (noodl35)

Re: (S14-NEO)

Re: (S14-NEO)

Re: (sickness14)

Re: (S14-NEO)

Re: (sickness14)

Re: (S14-NEO)

Re: (neonbomb)

Re: (Coolwhip)

Re: (sickness14)

Re: (Cjmartz2k)

Re: (sickness14)

Re: (S14-NEO)

Re: (l0nestar)

Re: (mott6904)

Re: (boosted98gst)

Re: (mott6904)

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