Side-Draft RB

[FJ 280z]

i forgot to mention one of the most important part in making a high hp N/A motor, the cams. im sure that 400hp rb30de has some huge cams, i bet thier custom, and i bet thier ♥♥♥♥♥♥♥ EXPENSIVE! and thats just a part of the cost, not including that mystery manifold for running sidedrafts. the headers!!! custom headers for an RB motor into a Z (who knows if the skyline headers, if you can find em, will even fit in a Z) from a good place like say full-race or something, would be over 1,000 bucks as well.

 

i guess i can say im a little biased against n/a. i built the ♥♥♥♥ out of a z24 engine before, mikuni 44s (sounded SWEET with the cam), webb 292 cam, alot of headwork, alot of block work, big exhuast, lightened the 720 body, too much nitrous, just to get SMOKED by these turbo honda punks who bought, not built, thier ride, so i said f**k that, im going turbo, and thats why im building my fj20det (ya i know) in my Z. im tired of farting around.... thats my rant, later kids..

[EMWHYR0HEN]

I'm currently running an NA RB25DE in my S30 and Iv'e actually considered both a carbed setup and a FI setup with ITB's.

 

Both of which I don't consider to be the best bang for the buck upgrades but, definatly unique and cool sounding.

 

However, here are the ups and downs.

Going carbs would enable you to keep most of your stock fuel systems whereas with an FI setup it would be best to upgrade your gas tank, fuel hardlines, and a bigger fuel pump. For both applications you would have to fab a custom intake manifold for carbs or an ITB setup. The last major thing for the carbed setup would be to ditch the stock direct fire ignition system and make your own ignition system and for the ITB FI setup, you would have to leave the MAF sensor and switch to a MAP system or standalone.

 

If your searching for more power I'd look into doing some of the old school tricks like larger disp.(RB30), headwork and maybe some bottom end work, cams, injectors, and some ECU tuning.

 

but that's just my 2 cents.....

[NZeder]

400HP efi, fuel injected, okay, lets toss that out the window...

 

rb31de carb'd? okay, maybe you put the E on accidentally, but the E stands for EFI, so how can it be a carb'd EFI engine? im guessing that was a mistake and its cool we all make em.

 

anyways, those are both rb30 motors, the largest of the rb series (as far as i know) and one of them is punched up (not by much) to a 3.1 but even still, there has to be some major work done to those because the rb30's are single cams, and they have to have a dohc head fitted on first, unless you find the super rare rb30de from the kaira m30 aka r31 gts-r. even still, the rb30de came with only 237hp, so alot of work would have to be done for that additional 100hp. where the rb25de has around 188hp even more work would have to be done to get it in the 250 or so range where it would be really fun....

 

Yes I think the RB31DE was meant to be RB30D - yes there is a lot of work to install a D or DE or DET onto the RB30 bottom end. Me I have gone like the other RB30DE that I know here in NZ with the RB26 head (I was going to do RB26DE but engine builder said more cc is better - so I sold the bottom end and the H-beam rods I had purchased). Resons and these are the same reason why the other guy build his two RB30DE using the RB26 head.

 

1. DCOE TB or Carbs are easy to fit to the RB26 intake

2. Solid lifter = higher RPM required for the N/A to make more power

3. RB26 heads have good valves and ports out of the box vs RB25DE non vvt head (easy to bolt on to the RB30 bottom end)

4. As number 3 no head mods to bolt on (ok yes need block mods for the larger head bolt/studs but need to mod the block for the twin cam anyway no matter what TC head is used)

5. Because RB26 are cheaper here in NZ than what you guys in the US have to pay my whole RB26 was under $2000 USD at the time (not now as the US vs NZ is very different now) which make the solid lifter of the RB26 worth it as to convert a RB25 VVT head to solid lifter would cost as much as the RB26 head cost me.

 

I don't get you first comment though EFI ok? What do you have against Carbs? A good dyno guy some good carbs and you will get excellent results. I am sure many can come up with good setups on carbs. I for one know of 2 L28 very simular in build, ok both are track cars (both are still road legal), one with carbs the other with triple TB's both have the same HP output, both have the same issues below 2000RPM and both go around the track within 0.5s of each other so where is the benifet in this case? The EFI L28 also has wasted spake vs dizzy on the other and both are strokers.

 

All this thinking about it I might just go carb too as it would mean less hassle in wiring in a ECU, I can use my existing fuel pump (when/if I EFI will need new = more $$) the list goes on.

 

Enough of that EFI-VS-Carb N/A vs Turbo this is not what this tread was about it was just about putting carbs on to a RB - any RB who cares if it is a RB20, RB25, RB26 or RB30 if you think it is a waste of $$ who cares it is not your car or $$ anyway. Rant over......

 

Here are some pics of N/A header just to get things back on track - I can't find my pics of carb's RB's but I will post some later.

 

PS: Yes his cams are custom and not that expensive really as he is using RB26 heads custom was the only choice and this is what I will be doing too and one of the pics attached is his customer headers. If you want to do this you can expect to spend $$ that is just it. Me if I was doing a DET I would still spend the same or more, balance, new H-beam rods, head work, new turbo manifold and turbo's, gaskets etc but that is me I just don't want to through and engine in and say it is done so it is relative really.

[Careless]

custom cams are not the only choice for an RB26 head. you can mix and match other RB26 cams to get the desired effects of overlap and proper duration/lift.

 

rb31de carb'd? okay, maybe you put the E on accidentally, but the E stands for EFI, so how can it be a carb'd EFI engine?

lol. relax man, small oversight. I think that you think too highly of the RB26, and I'm sorry my E offended you to some extent. LOL.

 

lets agree to disagree, and I'm sorry your Z24 didn't perform quite as well as you would have liked it to. I'm sure 350+ hp in a 2700 lbs car will be enough to make me happy.

 

If it were not for the fun factor in extracting power from an engine, and calculating small details that are imperative before assembly, I would have taken the 5 or 6 grand I've got in parts, and bought an LS1. I COULD put a turbo on my RB30, and fix the small issues after it's running and before I boost it hard enough, but then it's the computer thinking, and not the builder (me).

 

We can't win 'em all. I just pick my battles appropriately, and I'm not trying to compete against anyone with my car, I just want to suck in birds from telephone lines as I bounce off the limiter at 7500+ rpm on the quiet streets.

 

[savageskaterkid]

i guess i can say im a little biased against n/a. i built the ♥♥♥♥ out of a z24 engine before, mikuni 44s (sounded SWEET with the cam), webb 292 cam, alot of headwork, alot of block work, big exhuast, lightened the 720 body, too much nitrous, just to get SMOKED by these turbo honda punks who bought, not built, thier ride, so i said f**k that, im going turbo, and thats why im building my fj20det (ya i know) in my Z. im tired of farting around.... thats my rant, later kids..

 

 

Umm, on this one its not all about max power, if it was, you'd of picked the RB26DETT and called it a day, with a bunch of mods, but instead you picked the smaller motor, "no replacement for displacement" comes to mind. As with the way your talking about turbo is always better, then you seem to be the kind of person who uses this saying alot.

 

I'm not going for all out power. This is gonna be my cruiser. Will I goto the drag strip with it? Your Damn right I will. I'm not lookin for a 7 second car. I want something that will get out of its own way, sound nice, rev out real nice, and have the power to throw me back in the seat. I'm looking at an RB25, so it won't be messing with your "holy" RB26. I've come to relize that I don't wanna try and be the fastest, as someone will always be faster. I want a vintage look, but a modern powerhouse mixed with old school cool.

 

I have a single request though, if all your going to do is bash me in my own thread, then please don't post in it.

[Careless]

I don't wanna try and be the fastest, as someone will always be faster. I want a vintage look, but a modern powerhouse mixed with old school cool.

 

I agree with your reasoning.

 

But I don't think he was bashing you, he's just opinionated, as am I.

The only difference is that you and I share the same opinion on what we think our personal projects should be like, and he does not.

 

I guess it's a case of "been there, done that". Well, I've neither been there (NA high comp RB), nor have I done that (build a nice N/A engine on my own).

 

So here's to you, me, and nzeder, and FJ for contributing his thoughts.

 

 

 

Now... if someone can find what other mods that Rocky Auto or that jap s130 had... that'd be sweet. Hold on, I'll post some pics soon =)

[olie05]

http://www.r31house.co.jp/r31/vivi215.htm

[Careless]

yeah the R31 house video they have of the RB20 headed carb'd RB30

didn't impress me at all. =/

[Careless]

Ｓ１３０ ＲＢ３１

 

ＲＢ３１キャブ（SOLEX50トリプル）ＮＡチューン３６５馬力

気持ちいいです。

 

http://www.testarossa.jp/library/s130/index.htm

[savageskaterkid]

Anybody else know where to get a manifold.

[Nizm0Zed]

 

there is a beautiful C110 skyline, with a custom Rb20 red top triple weber conversion in it.

 

 

 

these last two are just car porn for the sake of it

[NZeder]

Anybody else know where to get a manifold.

I think they all will be custom to some form. You can get RB25DE headers from Fujitsubo (and others) that might work with minor mods so that take care of headers for RB20/25 heads. But RB26 = custom (Unless you find the rare RB26DE from the AUTECH R32 Skyline). Intakes will have to custom on any head but the RB26 first 1/2 of the intake before the standard TB's has 45mm throats that are almost (within a 1mm) the same as DCOE but the bolt pattern is different closer at one and further apart at the other. But an adapter should fix that - not sure if the RB26 intake will fit on a RB20/25 head? Anybody know the answer to this?

[Canadianz]

While I don't really "get" the idea of carbing an RB engine, its original and worth a try. However if your not stuck on using an RB why don't you use one of the toyota 4's that are swapped into the Ae86 corolla's ( I can't remember the engine code) they have 5 valves per cylinder and I think ITB's to boot. There also a bout the same price as the RB you are going to start with and make good power as well as spinning like 9k or something silly. So you have your old school/new school thing taken care of as the engines are pretty recognizable, as well they make good power and rev. To top it all there not an arm and a leg and have an after market, to my knowledge this would also be an original swap.

 

In response to the header questions my thinking is to adapt or go custom.

So go buy a really cheap set of ebay bottom mount headers for what ever RB block you buy, and also buy a set of old L-series headers. Chop the flanges off both sets, of headers, run the RB header flange through a mill and then weld on the L-series headers. The ports should be pretty close and as a result your going to get a bolt on set of headers that are already tuned for a inline six, without messing with spacers or adapters etc, and should be a helluva lot cheaper than getting a custom set made. Somebody should do some measurements on the port size and spacing and see if this might work ? Or even easier go buy a cheap bottom mount tubo manifold, and a t-3 flange. Weld the flange to your downpipe and bolt it to the turbo outlet on the bottom mount. Chop and weld the pipe for the wastegate and your laughing. Might not be efficient but it would be cheap, hell you could even use the stock header and use a turbo flange to adapt it to your exhaust.

 

 

 

If your totally set on carbing an RB, don't talk about it, buy one and build it, its not well documented so start reading how the L-series boys build theirs and transfer the knowledge over. Basically pretend you are building a stoker L-series in your head in which every part is hand built and that should give you a cost idea. Its hard enough finding RB parts let alone mysterious NA parts so start fabricating and good luck. Post your results on both threads and keep us updated. Basically every question you have asked can be answered in the L series thread or with the word custom.

 

As I say, if you want to do it, go ahead and do it, your money etc, I just don't see this build being very efficient. It would also suck to get bitten buy the power bug and switch back to turbo after it all.

[savageskaterkid]

If your totally set on carbing an RB, don't talk about it, buy one and build it, its not well documented so start reading how the L-series boys build theirs and transfer the knowledge over. Basically pretend you are building a stoker L-series in your head in which every part is hand built and that should give you a cost idea. Its hard enough finding RB parts let alone mysterious NA parts so start fabricating and good luck. Post your results on both threads and keep us updated. Basically every question you have asked can be answered in the L series thread or with the word custom.

 

I'm not going for all out power on this. Take a stock RB25DE, take off fuel injection, put header and carbs on, thats it. No stroker, no engine work, all stock. Maybe cams, thats about it. A header isn't a problem, as I was gonna see if I could just find a flange, or the cheap manifold and chop the flange and use the L header and just tweak it. I can weld stainless, and have access to a welder, so I can do that. I was just looking for the carby intake. I already have carbs, I wanna do something fairly original, and diffrent. I love the sound of a nice RB, but I have yet to hear an N/A one. Maybe I'll do a blow through triple carb turbo RB25. How original, and vintage/retro? But first I gotta get the thing running, then think about boost later.

[Careless]

there's a fellow on the r31skyline club forums that took an RB25DE, cammed it, put a "z0rst" (exhaust), put the head on an RB30 block, compression somewhere around 9.5 or 10, had a crappy tune on a 25DET computer (or DE, cant recall), and made close to 200 rwkw (270hp) using stock EFI with SAFC to trim the maps to get it running ok.

 

That's without ITB's, with improper fueling, somewhat low compression, and a head that does not flow as much or as well as the RB26.

 

I think 240 rwkw is possible, but I don't think you will get 200 rwkw with an RB25 head on anything that is carbed, much less an RB25DE block itself if you don't do some VERY fine work on the head, like enlarging the intake valves by 1 mm, getting a set of ugly cams, with some triple mikuni's, and pretty scribbling your john hancock all over the ports to get them to read right.

 

That's the reason why this seems so complicated and simple, yet unworthy of a trial/error. You won't make more power than factory unless you're ready to invest some time and money, and for whatever the case may be, I wouldn't start with an RB25 for that reason.

 

Go out in one direction completely, or go home. N/A relies on the head to allow enough air to enter the cyls with little loss in order to create a vacuum. Would you like to start with an inferior head? That's why I'm going RB26/30, it's the largest of the 4 and has the most potential to create more power (displacement + better flowing head).

 

Got a spare RB25 lying around that's missing parts? Try it. Gonna buy an RB25 to do it? meh... if it's what you want, try it! But I would look for an RB25 or 26 head and plonk it onto a 30 block if anything.

 

forget what carb you're gonna use or what you have. Forget what you need once you get the engine. Figure out whether or not you see this as an investment to make you smile, or something to beat on for a couple of years. Cause in the end, you may just want to go to the biggest/most potential possible, and considering the difference between the two starting points , and the small differences in options, it's easy to justify spending an extra grand or two to get the better of the two in order to cut out the chance of mechanical limitations in the future.

 

 

DO you wanna budget money for an RB25 head only to find the springs suck, and they can use some GTR love? The hydraulic lifters offer valve-train parasitic loss as one of it's key features, and the valves and port design needs to be reworked to match the GTR head and the cams are a little harder to come by, or not as wide-ranging? KNOWING that, I would try and find a GTR head (600 - 1000), RB30 block (800 - 1200), and then just have it honed and re-ringed with RB25DE pistons. You should have a 11.5:1 or so compression, and you can just squeeze a thicker gasket in there to get it down to 10.5:1.

 

You will make 180rwkw with those carbs, perhaps. Is that what you're looking to make?

 

I am budgeting 12 - 15k for my engine alone. If I make 365 hp out of it. I will be more than pleased. That includes machining, balancing, squaring everything up, and personal assembly and parts contracting that I've almost completed. Now I have to stick with it But I've never changed the plan, so it's ok.

 

 

I think it's a cool idea, but I'm curious to know where you see the engine being in your line up of cars, not how much power it will make... How long do you expect it to last, or how well do you want it to run?

 

 

Choose wisely. It costs money!!!!

[Careless]

Then again, if you have an RB25DE, and just want to make an intake and exhaust system to get it running to have fun in... well that ain't so bad either. It would probably make somewhere around 210 to 215 hp with a cam, header, and some port matching... not bad compared to some L's.

 

That I would live with. and that seems like what you want to do.

 

So, I'm all for it.

 

 

Who knows, you may like it enough to slowly start another better engine on the side. That's cool too!

[savageskaterkid]

Then again, if you have an RB25DE, and just want to make an intake and exhaust system to get it running to have fun in... well that ain't so bad either. It would probably make somewhere around 210 to 215 hp with a cam, header, and some port matching... not bad compared to some L's.

 

Who knows, you may like it enough to slowly start another better engine on the side. That's cool too!

 

This is exactly what I wanna do, a mild punch, and a nice revving motor, mixed with old school cool. It would deffinitly be an upgrade over my non running L28 setup, as someone may be buying the L28. RB25DE's are fairly cheap compared to turbo models, specially without wiring and ECU, it definitly knocks price down a bit.

[Careless]

This is exactly what I wanna do, a mild punch, and a nice revving motor, mixed with old school cool. It would deffinitly be an upgrade over my non running L28 setup, as someone may be buying the L28. RB25DE's are fairly cheap compared to turbo models, specially without wiring and ECU, it definitly knocks price down a bit.

 

well then there you go =)

 

if you can get the engine for under 1200, and find an RB20 transmission, I would go that route to have a running car.

 

The transmission is smaller and lighter, and could help with lugging the car around with 250 or so hp.

[NZeder]

RB25DE's are fairly cheap compared to turbo models, specially without wiring and ECU, it definitly knocks price down a bit.

If you think about it this would a about the cheapest way to go if you want that RB DOHC look while still on a budget. Not ECU or wiring changes, no fuel tank/fuel line issues (assume you have a carb 240z already). Just need RB25DE engine and box (the RB25DE box is the same as the RB20DET), electric fuel pump, some triples on a custom manifold (you might have these already on a L24/L28), rear sump, engine and gearbox mount and you are away. The power gain over a L28 would be nothing or less but if it is the look you are after you will have it

 

If you have an earlier 240z shell it would be better to use a KA/CA/SR box and install the RB bellhousing as the tail is longer and the gear leaver would be in the correct location for the 240z shells that had the A box originally but you would then need to shorten the drive shaft.

 

This would get you up and running with RB power/look quickly you could then save the $$ for a RB30 bottom end and do the DOHC conversion to this, then in a weekend swap out the RB25D and put in the newly build RB30D for more power.

[savageskaterkid]

Its actually an FI 280Z right now, but I shouldn't have a problem as I have an electric pump good for the triples. A little looking online has showed that the RB25DE puts out about 190hp, I dont' see loosing that much horsepower by going to carbs, that it wouldn't even be an upgrade from the L28.

 

I saw that you could actually use the L28 trans behind the RB motor, but the idea is frowned upon as it won't handle the abuse of an RB25DET over a long period of time. But since this is N/A, and not too much more power then a stock L28, that it should handle quite well for awhile. It would also make it a bolt in affair(cheap) where I wouldn't need a new driveshaft or have to make a trans mount.