# Is this possible on an RB25?



## Jimefam (Apr 30, 2011)

Hello I have been building my R33 RB25 for a few months now with the stated goal of getting to 1,000HP and running it in my 1989 240sx. I have tried to use the best components that I could find and to do as much as possible to make this figure possible and relatively reliable. However as my build has progressed I have decided to build a much more dedicated drag car than my original goal and will now be running the car in our X275 class against mainly BB V8's with much larger turbos than what I will be running. I will be having a 25.5 chassis and ford 9" rear end with tubs and a TH400 but the truth is 1,000whp isn't going to cut it for me to be competitive in that class. The leaders in that class are running right around [email protected]+ and [email protected]+ and in speaking with my chassis builder I'm being told I'd need around 1300whp with a decent curve to be able to run against top cars in that class with a minimum weight of 2800lbs. Anyway to make a long story short I've replaced every single thing on the motor except for the bits that would no longer make it an RB25(Head,Block,Crank) the head has been ported VERY well and I'm fairly confident I can flow near what top RB26 Heads can but I'm worried about the Crank and Block not being up to the task. I can obviously upgrade to an N1 Block or a Billet Crank but there are no such things for an RB25 and that would mean abandoning the 25. Making that high of power with a 25 was kind of the point so I'm really hesistant to swap unless absolutely necessary. I also recently found out about Project GTST which had me giddy for about 10 minutes until I saw he had ditched the 25 in favor of the 26. I'm posting this on here because pretty much all the high HP RB builders seem to post here and maybe they can offer advice. Here are my options as I see them:

1. Procede as planned and go simply for 1,000WHP out of the 25 and accept not being that competitive in my class.
2. Go for Broke and try to get to the 1300WHP out of the 25 and risk blowing the whole damn thing(I know I'm risking this with number 1 also)
3. Say F the 25 and buy a billet crank and N1 block.

#3 is definitely my least favorite because I wont accomplish what I set out to do regardless of how much power I make on a 26. If I blew my 25 it wouldn't be the end of the world or anything and I'd just go to #3 but not being a shop and being that I'm building this with no sponsors and in my garage it would be a while if I had to replace the whole motor. Wish I'd found this forum about 6 Months back! Here's a list of what I've got and a link to my build thread. Thanks for any advice guys. Oh and I'm gonna be running it on E85.

Every engine component including the block and head have been Cryo Treated
NOS direct port nitrous kit
R33 RB25DET bored 0.40 and line honed
Precision PT7685B
Head fully port and polished with top of combustion chamber coated
Haltech Platinum Pro
CP pistons 87mm (0.40 over) Coated on top and skirts
Upgraded tool steel wristpins
Carrillo Pro H Rods
Balanced and Bullnosed stock crank
acl main and rod bearings with calico coating
arp main studs
arp head studs
arp exhaust studs
tomei cam cap studs
tomei procams 270 duration and 10.25 lift
supertech oversized valves w/ Competition valve job with the face and stems coated
supertech dual valve springs w/ titanium retainers
supertech valve seals and locators
tomei solid lifters
tomei valve sheets
Barnes 5 stage oil pump
Custom 4 scavenge shallow sump
head oil drain return mod
tomei oil restrictors
Nismo N1 water pump
tomei adj cam gears
Greddy Intake plenum port matched
full-race Power turbo manifold
x2 synchronic 50mm WG's
Synchronic BOV
Haltech HP6 Igniter
splitfire coil packs
tomei 1.5mm headgasket
PWR Air to Ice Barrel 
Trust oil cooler
oil filter sandwich plate
Trust oil filter relocation kit
Greddy timing belt and drive belts
ati race crank dampner w/glimer belt drive
ati RB/TH400 adapter
Fuel Injector Connection 2200cc injectors
Custom -10 AN Fuel Rail
RCI 5 gallon fuel cell
x2 A1000 Fuel Pumps to one -10AN Feed Line
aeromotive fpr w/ -6 return
koyo radiator
nismo thermostat
greddy oil catch can
silicone radiator hoses and coolant hoses
dual puller electric fans
dual fan controller

It wont let me post a link so here is the link just add the dothtml at the end

forums.nicoclub.com/rb25det-1000hp-build-t532397


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## Nigel-Power (Dec 16, 2009)

A member on here "trackday_Addict" has got a RB25 GTS-t drag prepared Skyline, you might find it interesting to have a look at his project threads.

I'll post a link for you if I can dig them out.


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## Red R Racing (Aug 22, 2009)

having screwed together a few 1000hp+ RB's id say that 1000hp is obtainable with a 25 (solid lifter) based engine. The above combo looks ok but you may not have enough camshaft for your target. You will find especially on the exhaust side this will not allow the valve events required to reliably run at that power level. Excessive cylinder pressure will be the issue given the tune up required to make the numbers and your pins and little ends will cop some punishment. Combine this with the dry sump vacuum levels (if too high) robbing this area of lubricant, may be fairly busy doing lots of rebushing and pin replacement. Thats before you even consider what the spray will do over the top.

Id suggest a bigger overlap cam combo with the biggest lift you can for the duration selected. Block needs to see grout to the base of the water outlet that feeds the turbo. Coolant cavitation and distrubution will need to be addressed also. We normally use a custom girdle stud and head stud set-up that uses a larger main stud and different material head stud.

Ive spun stock cranks to 11500rpm fairly often so as long as the balancing and prep is right it should not be a problem other that the harmonic issues that come with revving an 8 counter crank to those levels


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## de wonderful (Apr 28, 2011)

Good luck sounds like a mental project.

What fuel BTW?


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## Red R Racing (Aug 22, 2009)

de wonderful said:


> Good luck sounds like a mental project.
> 
> What fuel BTW?


E85

we have run 1017hp and 1074hp at all four with E85 under competition conditions in a customers R34 the first couple of times we took it out. Thats around 1000kw at the flywheel which is around 1350hp and your target. That was a 2.7 RB26 based build though.

go for it!


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## Jimefam (Apr 30, 2011)

Nigel thanks I'd love to see that if you can find it. I'll look also.

Red- thanks for the insight. I hadn't thought it safe to rev past 10k, can I really go that high safely? Proline racing engines is Doing the machine work and I had told them to balance it for 11k but really never intended to run it so high. I hadn't thought cavitation would be a problem as I'd seen a few RB's here running 10k with the N1 pump without issue but I can imagine that higher than that I will have to do something else. Any recommendations? I will look into having some custom cams made as I don't recall seeing bigger cams for the 25(but hadn't really looked as I thought I'd be okay) suggestions here are welcome also  I really appreciate the suggestions and keep them coming if you think of anything else.

Wonderful- huh? I don't understand what you mean sorry. It will be a custom blended E85, I have a ethanol plant nearby and they will sell me 55 gallon drums of E98 blended with a race fuel of my choice(I'm thinking C23?) I could run straight E98 but I don't think I'd have enough injector for more than say 1100whp.


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## Jimefam (Apr 30, 2011)

Oh as for the bearings wearing and all that I'd hoped to be able to freshen the engine up every 100 passes or so. What would be too much vacuum for the dry sump? I'm learning as I go so I may ask some head scratching questions!


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## de wonderful (Apr 28, 2011)

I was just asking what fuel, not a rhetorical question.


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## Al_Star (Aug 22, 2007)

bradshaws old Rb25 died last july, i know because it was in mine


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## trackday addict (May 14, 2005)

Mate without bursting your bubble you are dreaming if you think you will get 100 passes without any issues and then only a bearing refresh !
More like 3 or 4 blown blocks, lots of learning and then maybe a way forward.

Sorry not meaning to be negative just realistic, at the power you want things are not exactly a walk in the park but good luck with your project. 




Jimefam said:


> Oh as for the bearings wearing and all that I'd hoped to be able to freshen the engine up every 100 passes or so. What would be too much vacuum for the dry sump? I'm learning as I go so I may ask some head scratching questions!


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## Jimefam (Apr 30, 2011)

de wonderful said:


> I was just asking what fuel, not a rhetorical question.


Lol no I understood the fuel question just the mental project part wasn't an expression I'd heard and it threw me for a sec but I got it after(sorry I've now been up 40hrs straight)

Nigel- I found the trackday addict threads and he's actually the owner of the Project GTST car I mentioned in my first post. I wrote him a few questions from my wifes facebook but then I saw he has a 26 in it not a 25. Still an amazing car though and it's crazy the great amount of RB builders on this forum. I've pm'd [email protected] a few times and he's always responded candidly and quickly.


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## trackday addict (May 14, 2005)

We ran an RB25 in 2006 and 2007 with over 850 at the hubs and was very reliable but extra grunt via the rb 26 required.


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## Jimefam (Apr 30, 2011)

trackday addict said:


> Mate without bursting your bubble you are dreaming if you think you will get 100 passes without any issues and then only a bearing refresh !
> More like 3 or 4 blown blocks, lots of learning and then maybe a way forward.
> 
> Sorry not meaning to be negative just realistic, at the power you want things are not exactly a walk in the park but good luck with your project.


No problem I appreciate the feedback and truth. I can only try to anticipate as many screw ups as possible but your absolutely right that this will be a huge undertaking for someone as ignorant on the topic as me. Hopefully some of the feedback and pointers I glean off of this thread can reduce those blown motors if only by 1. When you switched to the rb26 was it because of a limitation in the RB25? Thanks for any advice.


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## trackday addict (May 14, 2005)

Hi - pure bhp really and much easier via rb26 as done hundreds of times before and proven. If you want to plough down the 25 route then you are looking at serious development costs


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## Mookistar (Feb 5, 2004)

Can I ask why you've chosen the 25? Does it do anything inherently better than the 26?


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## Jimefam (Apr 30, 2011)

trackday addict said:


> Hi - pure bhp really and much easier via rb26 as done hundreds of times before and proven. If you want to plough down the 25 route then you are looking at serious development costs


Ahh got it. It's just overall not up to it, well I suppose at this point I'll run her as planned(with some of the changes recommended on here that are still easy and feasible to do) and she what I can get out of her. If I'm gonna need rb26 head block and crank there's no reason not to push the hell out of this one lol. It'll be the first of the three or four I guess lol. 

-Mookistar no advantage that I'm aware of I just bought the 25 when I was 22 and couldn't afford the extra couple grand for the 26! She blew this year and I thought F it let's try and build the baddest RB25 I can. As trackday stated the 26 has made huge #'s hundreds of times so I figured let's see if the 25 is capable of breaking the 1k mark and remain somewhat together. As I read trackday say in another thread when I was told to read his posts today, he said he choose rwd over awd because at the time awd was believed to be the only way and he wanted to do something else. I'm sure I'm not gonna prove the 25 is better than the 26 or anything like that(I'm sure it's not) just figured that most people when they decide to make BIG power automatically go for the 26. Which would make sense and I probably would have done the same if that was my goal from the beginning but it sort of evolved gradually. I figured now I'm 26 and can afford to play with it alittle more let's see what's here.


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## bigkev (Mar 2, 2008)

while i applore the R&D undertaking of using the RB25 for such a task, i think you're concerned by its limitations too early in the project. building this engine and car is only really the start of things. so as others are suggesting . . . why start with the 25? i doubt its because you had one lying around the garage. if you're likely to spend 100k on this car you may as well spend an extra 2k on a 26?! if i planned to spend big money on a big spec drag ford capri i wouldn't hunt down a 1.6 popular, id find a 2.8 or 3.1 for example.

i hope this post doesnt come across too negative as im really totally behind it mate, but make sure you're embarking on the right path from the start.

good luck with it either way mate:thumbsup:

kev


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## bigkev (Mar 2, 2008)

ok i obvs didnt see the above post before i posted my reply

thats 5mins of my life ill not see again:nervous:


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## Jimefam (Apr 30, 2011)

bigkev said:


> while i applore the R&D undertaking of using the RB25 for such a task, i think you're concerned by its limitations too early in the project. building this engine and car is only really the start of things. so as others are suggesting . . . why start with the 25? i doubt its because you had one lying around the garage. if you're likely to spend 100k on this car you may as well spend an extra 2k on a 26?! if i planned to spend big money on a big spec drag ford capri i wouldn't hunt down a 1.6 popular, id find a 2.8 or 3.1 for example.
> 
> i hope this post doesnt come across too negative as im really totally behind it mate, but make sure you're embarking on the right path from the start.
> 
> ...


I've spent close to that but that will be for the entire car not just the motor. If I want to change to a 26 or 30 later on everything besides the longblock can carry over without the slightest adjustment. Another thing that maybe I didnt specify in the first post is that that list I posted isn't some wish list that I plan on running. It's all paid for and in my possession or at the machine shop. The chassis is already paid for and the rear end everything is already here in my garage I'm just waiting for a slot to open up at the chassis shop. In fact my motor is already done and I created this thread because I thought 1000whp would be the limit of the 25 crank or block and hoped I could get there but wasn't sure. I'd seen a few in the 800's online but no higher. I created this thread because as I said my goals have been evolving and now to be competitive in the class I want to run(X275) I would need 30% more power than what I was hoping the 25 could handle and wasn't sure if I should throw out my already machined block and crank and purchase an N1
Block and Billet RB26 crank or if there was a chance the 25 equivalent could hold. I figured someone was gonna say "no the limit on the 25 block has been shown to be X and you cant do it" or the same about the crank.


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## bigkev (Mar 2, 2008)

in that case i wish you the best of luck with your project. keep us updated please.:thumbsup:


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## Jimefam (Apr 30, 2011)

bigkev said:


> in that case i wish you the best of luck with your project. keep us updated please.:thumbsup:


Will do. Here's another thought that occured to me right now. How about if I sleeved the RB25? Darton makes some sleeves for the RB26 could I use these on my 25 to strengthen the block and would this allow me to reach the power I'm looking for more safely? I actually have a decent hook up on Darton Sleeves and could get them for a very reasonable price and having them installed wouldn't be a big deal either.


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## Red R Racing (Aug 22, 2009)

the weak point of the block in the 25's is no different in a 26. All the additional bracing in a 26 is around the pan rail far below the centre rib which both blocks have. If Nissan didnt cross the block through the centre with the oil feed and went around the front like Toyota this would have allowed additional iron to be put there when they cast them and the cracking would not be an issue.

Come to think of it ive built a few 700hp RB25's and haven't had any block issues. Only RB based block that has given reliability issues is actually the 26 but statistically we build more of them and push them a lot harder than the others.

Maybe look at running a girdle to pan rail brace might be a good idea as this will lock everything together and minimise twisting. like this one here...

Engine Cradles

In my opinion vibration is the real enemy though as the vibration disassociates the molecules in the cast iron and causes heat. This is where cracking originates and tends to begin where impurities are cast in during block construction.

Id suggest using VP Import to blend with the ethanol, this has netted the best results from all of the petrol based fuels we have tested. The piston speed in what you are building will be very high and fuel does some strange things chemically when compressed at a higher rate i.e. what is safe at 9500rpm is not necessarily safe at 11500rpm even if the tune numbers and boost levels are the same.

This level of engine is not for the beginner or the short pocketed. One $30,000 engine blow up can quickly remove all the fun out of it. If your not prepared to fund it to this level of commitment and hurt some parts along the way id suggest maybe going down a well worn path. Id really like to see you stick to it though and you must be aware of the situation but in reality you can destroy any engine at this level of tune if you don't have everything 100% spot on. If this wasn't the case everyone would be doing it.

good luck with it.


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## R.I.P.S NZ (May 7, 2004)

1000hp and 1300whp are 2 very different things, 1 is about 1.5 times as much as the other.

If you get no break for engine size and you have to weigh 2800lb you really would have your work cut out for you to run with the turbo V8 guys.

What transmission are you looking to use?

A 275 tyre makes it even harder so you'd need a huge amount of chassis work and top class boost control to hook up well.

If you find the 25 doesn't cut it, personally I wouldn't waste my time going to a 26, its just not enough of an increase in displacement, a suitable 30 could give you 1200-1300whp through the right transmission and we did over 100 runs with an oil change and a set of spark plugs so it is "possible"

If your fixed on sticking with 2500cc get a real good 26 head on it or at the least get the 25 head ported properly and running solid lifters and bigger cams etc.

Good luck,

Rob


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## Jimefam (Apr 30, 2011)

R.I.P.S NZ said:


> 1000hp and 1300whp are 2 very different things, 1 is about 1.5 times as much as the other.
> 
> If you get no break for engine size and you have to weigh 2800lb you really would have your work cut out for you to run with the turbo V8 guys.
> 
> ...


Rob

I've got a coan racing TH400. There is a company here called ATI that makes an adapter plate that bolts on to RB Blocks. Yeah obviously there's a pretty large difference between my original 1000whp goal and the 1300whp I would need to run well in that class. I do have an advantage in weight as the BB V8's have to weigh in at 3300lbs and are limited to one power adder whereas I can run both nitrous and turbo. A very good time for the class is 5.0's in the 1/8 and the quickest run in the class is 4.91 I believe.

I'm having a fabricated 9" housing with strange ultra aluminum bolt thru center section and their 40 spline axles being made at the moment. An adjustable 4 link and double adjustable coilovers will be installed along with a chromoly 25.5 cage in a few weeks as soon as space opens up at bell chassisworks. The head has been ported pretty aggressively by Proline Racing and I've already got solid lifters in the head. I'll probably need bigger cams and I'll begin looking for custom cams this week. I'm running a Haltech Platinum Pro and will be going to Haltech USA this friday to discuss finding a suitable tuner here in the states. I pm'd that member on here you recommended for feedback but never got a response. Steve Petty from Proline can tune the engine and is one of the top drag V8 tuners in the states but has never tuned an RB though he has tuned 1000+whp 2jz's. I will see what is the most I can get out of the 25 and when it goes or if I need more displacement your right it's a 30 for me and we'll be in touch as who better to get a 30 from? Thanks for the feedback

Red- that's an excellent looking cradle and something I wasn't aware was made for RB's. I've shot Hi Octane an email as they were the only dealer who I found a webpage for. What say you though on the Darton Sleeves coupled with that Cradle? And if I use both would you still recommend grouting the block? Although all the machine work has been completed I don't believe they assembled the motor yet as I spoke to them on Thursday and they were gonna begin assembling the head this coming week. I'm still at a point where I can make the change to sleeves rather easily. Thanks for the head up on the VP Import. Yes I'm aware that I can at the slightest mistake lose the motor and will slowly begin anew if necessary although not with a 25. I'll do all I can this go around to strengthen and support the 25 but if and when this motor blows I will go to a proven RB30. It's taken me almost 4 months to get all the components together and have it all machined and ready to go so I've got some patience.


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## R.I.P.S NZ (May 7, 2004)

4.9 - 5.0s @ 150 is what I ran in the 240z with a pretty big tyre, TH400 and at just over 2800lb. 60fts were 1.25 and it went on to 7.8s on the 1/4.

If your only ever running the 8th you could run pretty low gears but then traction will be even harder to get with the tyres you have to use, I reckon you'll just have to get her going, see how it goes and wind her up as you and the chassis get sorted.

Main thing is to be VERY sure you have a good tune, not only will you make power easier, it will be far more reliable as well,

Rob


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## Jimefam (Apr 30, 2011)

R.I.P.S NZ said:


> 4.9 - 5.0s @ 150 is what I ran in the 240z with a pretty big tyre, TH400 and at just over 2800lb. 60fts were 1.25 and it went on to 7.8s on the 1/4.
> 
> If your only ever running the 8th you could run pretty low gears but then traction will be even harder to get with the tyres you have to use, I reckon you'll just have to get her going, see how it goes and wind her up as you and the chassis get sorted.
> 
> ...


Only reason the times are so low is that SGMP and Atlanta dragway(my local tracks) are two of the best in the country with SGMP in particular being very well prepped all the time and the site of most of the records for small tire racing. The same class in other tracks around the country routinely run .10-20's slower so I'm facing less competition the ET's would indicate. From seeing your runs and reading your comments if memory serves me your usual track isn't the quickest(rollercoaster I believe you termed it once) so I'm sure your car and mine would be worlds apart even if I were to ever be able to get close to your ET. I have to run 2800lbs to meet weight in the class and use 275's but I will be adding weight bars to get there as I weighed 2220 with the 25 in there before(I've done alot of lightening to the car) and will probably be at 2500 now with me in it. I will also do a mini tub that will allow me to run a bigger wheel so I will probably throw a 33" tire on there and get it as light as she can occasionally for fun and see what I can run.

Ahhh the tune that is the biggest question mark still left in my combo. One thought that had occured to me is that Titan Motorsports is in Orlando only a 5 hour drive away and they have tuned countless 1500whp+ 2jz's which is as similar to an RB as I can get in the US. There are plenty of people who have played around with an RB but no one near that level of power. Oh and I've got a 5.14 Richmond Gears R&P that I will try first and see how it goes.


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## R.I.P.S NZ (May 7, 2004)

Get the tallest tyre you can under there if your only limited to width.

Your on the right track, just keep it simple, get started and see how it goes.

Rob


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## Jimefam (Apr 30, 2011)

R.I.P.S NZ said:


> Get the tallest tyre you can under there if your only limited to width.
> 
> Your on the right track, just keep it simple, get started and see how it goes.
> 
> Rob


Thanks for the encouragement. Actually the biggest I can run in the class is 275/60/15 and I'm running Hoosier Dot Radials on Billet Specialties 15X10.5's.


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## Red R Racing (Aug 22, 2009)

you dont need custom cams, GTR cams will work if you have converted to solid lifter.


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## Jimefam (Apr 30, 2011)

Red R Racing said:


> you dont need custom cams, GTR cams will work if you have converted to solid lifter.


Yes but I used the Tomei Solid Lifter Conversion kit not the GTR solid lifters is it the same? Tomei makes a 290* 11.50mm Lift IN/EX would that be a good choice? What about the Sleeves? Should I still grout the block as you suggested earlier or would the sleeves be sufficient? Thanks


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## Red R Racing (Aug 22, 2009)

Jimefam said:


> Yes but I used the Tomei Solid Lifter Conversion kit not the GTR solid lifters is it the same? Tomei makes a 290* 11.50mm Lift IN/EX would that be a good choice? What about the Sleeves? Should I still grout the block as you suggested earlier or would the sleeves be sufficient? Thanks


What base circle is it set-up for ? Id go for the biggest sticks you can get for whatever its set-up for now. The cams you have suggested are much better for the application than what you have now. I think the lash caps in the Tomei kits are the same as the GenIII chev items so if you have to go a smaller b/c you could re-shim it with those.

I wouldnt sleeve the block id 1/2 grout it.


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## Jimefam (Apr 30, 2011)

Red R Racing said:


> What base circle is it set-up for ? Id go for the biggest sticks you can get for whatever its set-up for now. The cams you have suggested are much better for the application than what you have now. I think the lash caps in the Tomei kits are the same as the GenIII chev items so if you have to go a smaller b/c you could re-shim it with those.
> 
> I wouldnt sleeve the block id 1/2 grout it.


Ok I will talk to Tomei USA tomorrow and make sure I can run those cams and if not I'll get what I need to make it work. I'm surprised about the sleeves vs grouting as I thought the sleeves would be at least as strong and not limit cooling as the grouting would no? I'm not saying it's wrong as I don't know about this just curious as to what the benefits of one vs the other and I'd love to learn. Thanks again for all the input.


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## Jimefam (Apr 30, 2011)

Thought I would bump this to give a little update. Been a long ass 2.5 years building the car and motor but im real close to seeing what the 25 will do. These past couple days we had the car on the dyno getting the tune close enough to allow us to get on the track and finish it off there. We made a final total of [email protected](3.4bar) and the motor seems to be doing great. Of course the dyno is not the track and any motor can make a couple glory pulls so we will see how she fares on the dyno but so far im exceeding my goals and feel lucky to have not gone through the first of the 3 or 4 engines it is predicted I will blow up. Actual track results will be available soon as the weather clears here.


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## stephenwap (Mar 26, 2010)

Nice work mate, and nice patience to have kept at it for this long


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## Simonh (May 24, 2002)

some build pics would be great


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