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Rb20 Neo


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I am raising this thread to see another nice rays of sunshine after a bit of break.

First of all, Hello, I'm new member in here. I actually live in Finland but I find getting any useful information in Europe way too hard so here I am.

I am currently starting a build of '79 200B SSS (known as 180B in here but chassis is 810). Original L18 engine with dual carbs is not going back. Car has to have no more that 168 hp to meet legal regulations. I weighed some options in my mind and I found by accident RB20DET without turbo or manifolds for next to nothing so I bought it before anyone else had a chance.

My initial idea was to make it NA as it has 212 hp stock and it is really hard to "detune" it so that it meets regulations with turbo. I stumbled upon this thread in my journey for information about RB20 heads and I have found NEO head very interesting for a swap to "silver top" RB20DET bottom end and running it NA. CR is a great mystery, but for NA I am not going below 10:1 and I prefer something 10,5:1 -ish.

Something that catched my eyes was

On 8/15/2013 at 7:49 AM, BenR said:

*******

But because of the ridiculous tip heights on the valves you need to run solid lifters from a renault on the exhaust side and solids from a ka24de or a toyota tacoma on the intakes, and you'll need 1.5mm shims on the inlet and 3mm on the exhaust.

*******

I really hope BenR could catch up if he has more information about this engine he built (and has probably scrapped it already years ago). This is still a long shot for me as the build is just about to begin with all rust problems etc. but for now, information is what I mostly need. I work as mechanical engineer so I at least have an illusion about knowing something engines and I have access to some manual machining equipment.

Thanks for any info you have, I mean ANYTHING is a plus. and if someone asks, 6 cyl just for the "cool-factor" and audio. There is no good reason to do this what I can think of but hey, it's something completely different and should meet legal requirements.

 

Cheers.

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I really don't think i will be able to help you in regards to what BenR has said mate, however i do have info relevant to this thread.

Should be picking up an RB20DE Neo with only 60,xxx km on in in the next day or two. Was purchased through a reputable wrecker in Melbourne with evidence of genuine km.

I am currently running an R32 RB20DE with fully refreshed standard head and no modifications to the bottom end with an EFR6758 on it. I would have stuck with that engine combination if the RB20 Neo didnt come up so cheap.

Just to confirm @FinnDatsun you have an RB20 Neo or Vanilla silvertop RB20?

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I think I lost my thought, it was 2 am at the moment here.

Engine has to be dynoed, and there is some sort of common practice that if you have a turbo, it should run "reasonible" boost.

My first interest would be information about how the head bolts to silver top block, combustion chamber volume for CR calculation and so on, to see if it would even run. BenR seems to have all this info already and the valvetrain modification is a curiosity for now. But being able to rev never hurts now that head should have better flow figures to start with.

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  • 8 months later...
6 hours ago, sav man said:

Bumping this thread up again.  Anyone know where I would be able to find a RB20 NEO, I really only want the head but will take a complete engine if avaliable.

1. Try the for sale section

2 Try advertising in the parts wanted section

3 Ring around the wreckers

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17 hours ago, iruvyouskyrine said:

I have a complete RB20 Neo, absolutely immaculate and only 60xxx Km on it. Honestly i am not looking to sell but if you throw me a stupid high offer i may let it go. PM me if you want.

I tried to PM you, but forum said no

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  • 2 years later...

Bumping this up

So, I have been doing some small and big thinking and shopping for my ultimate NA RB20 fetish.

So far I have:

- Tomei solid lifter kit
- Tomei valve springs
- Tomei procam intake 270deg  9,25mm lift
- Tomei procam exhaust 260deg 9,25mm lift
- Adjustable cam pulleys
- Crank collar
- Kevlar belt
- 1,0mm head gasket + OEM gasket kit

Plus some proper wizardry to bottom end:

- Modified Renault connecting rod with 128mm end-to-end distance
- Suzuki GSXR pistons 13,0 CR

Plus on intake:

- 2x GSXR 750 ITB's (42mm) to be modified for 6 cyl

And bits and pieces from new cam cover bolts to woodruf keys etc. etc.


Sooooo... I have been looting for parts over several years and I don't anymore think about the cost of this monstrosity. Basically my aim has become to replicate Triumph Speed Triple 1050cc engine in staight-6 form. Engine geometry is shockingly similar with Triumph and half of RB20. My displacement will be 2100cc with 80mm pistons. My rod/stroke ratio will be at some 1,8 and I will lose 200g weight from moving components per cylinder, so 1,2kg moving mass in total. Plus whatever they need to machine away for balancing. CR will be something between 10 and 11 (RB has more CC in head than Gixxer), but I might need to bump it up by machining the head. Trying to set intake cam for power band target and adjust exhaust cam for feasible overlap for NA. I might have to go for GTR cams later if these are "too mild".

The head will be the last big question mark in the build, mainly its flow. I will go with stock valves just for sake of minor cost reduction to avoid going bankcrupt. Some serious porting is needed. But the aim will be 240hp+ in NA at ~8500 rpm or so. I still need harmonic balancer, shims for valves and ECU. And of course all the fabricating of intake and exhaust. Plus balancing and machining.

I must have lost my mind to do all this for such small engine, but it's all-in at this point.

At least there is no other like it in the world lol... plz help...
 

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I should have bottom end experiencing 1.5 times the load at 10.000 rpm compared to stock parts at 7200 rpm. Let's see where the redline sets, but I think bottom end will be just fine with main journal girdle and the fact it can take 400 hp in stock form turbo. I'm more worried about the head and stock valves, what kind of acceleration they experience during high revs. To have peak power in 8500 I should be able to rev it to 9500 just for sake of power band. Otherwise I need to lower my expectations overall.

One thing to consider also is that RB has 45deg angle between intake and exhaust valves in head, and by my limited research online the particular Gixxer has 40deg angle, so there is a valid risk my valve clearances to piston need to be plenty. Gixxer also has 28.5mm intake valves compared to 30mm of RB20 so I really hope aftermarket pistons have extra diameter in valve pockets to accommodate possible oversized valves.

With this conrod-piston combo, deck height is exactly the same as stock RB. But reduced piston and connecting rod weight, and longer rod will be easier on piston acceleraton and load. Rod is H-beam.

Not going to be ready anytime soon, but some day

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Any RB at 10k RPM will sound sensational however we all know RBs aren't the world's smoothest inline 6 either (let's face it, it's no Yamaha 1JZ or 2JZ) so the harmonics will be a fun thing to combat.

The ITBs would definitely add a fantastic soundtrack!

Very interested in the final product, good luck!

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On 3/16/2022 at 4:02 PM, Dose Pipe Sutututu said:

Any RB at 10k RPM will sound sensational however we all know RBs aren't the world's smoothest inline 6 either (let's face it, it's no Yamaha 1JZ or 2JZ) so the harmonics will be a fun thing to combat.

The ITBs would definitely add a fantastic soundtrack!

Very interested in the final product, good luck!

What harmonics in particular? I don't know too much about what happens at 10k RPM for these engines.

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On 3/17/2022 at 7:45 AM, joshuaho96 said:

What harmonics in particular?

Standard torsional harmonics as per every straight 6. Toyota/Yamaha just do a much better job of other aspects of the fundamental engine balance and oil pump drive and harmonic balancer integration and so on than Nissan did. The RB is a bit of a grandfathers axe, having its roots back in the 60s.

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On 3/16/2022 at 5:01 PM, GTSBoy said:

Standard torsional harmonics as per every straight 6. Toyota/Yamaha just do a much better job of other aspects of the fundamental engine balance and oil pump drive and harmonic balancer integration and so on than Nissan did. The RB is a bit of a grandfathers axe, having its roots back in the 60s.

Yeah, I'm just curious as to the specific elements that are worse on the RB and whether those are fixable. I know about the oil pump drive but the other parts I'm fuzzy on.

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It is known RBs don't like big rpms, however that's probably more to do with the factory crank and how they're balanced. A stroker or modified factory crank (knife edged, balanced, etc.) would not have the same flaws (characteristics? LOL) as a factory oil pump assassinating crank

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On 17/03/2022 at 10:14 AM, Dose Pipe Sutututu said:

It is known RBs don't like big rpms, however that's probably more to do with the factory crank and how they're balanced. A stroker or modified factory crank (knife edged, balanced, etc.) would not have the same flaws (characteristics? LOL) as a factory oil pump assassinating crank

Yes absolutely. My Nitto 2.8 full counter weight billet crank came with a balancing report that it was tested to 10000rpm, and Nitto rate the 2.8 kit to 11krpm. The 2.7 kit interestingly is rated to 12krpm.

The 2.8 billet crank weighs substantially more than the factory item too.

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  • 3 months later...

Hey all, thinking about letting go of my RB20 Neo that i have had tucked away for future projects in the shed for a long time. Removed from R34 with 46xxxkm on it, it is the cleanest used engine i have ever seen. Had not a single bit of rust or corrosion on it and the zinc plating was on every single bolt.

Unfortunately 'future projects' look to be infinitely located in the future so i really have no need for it any more.

Thought i would let people in here know as this is about the only thread in existance that talks about these things haha. If its not appropriate admin feel free to remove.

Located Newcastle NSW happy to post pics if admin approves.

Thanks

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