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docaam

Na Rb26/30 Built .....help Need

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Hi guys I have been on this forum reading for past year or so very infomrative considering I had no idea about these RB engines a year back ( still noob). For this this topic I did search and read some threads but they were very old threads so rather then bumping them starting a new one for get some answers.

I have an S30 project which is almost done running a RB25DETT Neo in it. ( thread on hybridZ http://forums.hybrid...60#entry1025367)

I want to do a RB26/30 NA engine and run it on triple carbs same like people in Japan doing it. The purpose of the car is occasional track days, weekend /daily drive during winter time (it gets really hot in summer here in dubai). I dont need a very high rev engine I can live with 6.5-7k in the beginning.

I bought a RB30NA engine off a Nissan Patrol and also got hold of RB26DETT head as well. I also got an adapator plate from a bloke in New Zealand which can fiit DOCE carbs on one side and from behind it will fit on stock RB26 intake manifold, there is also modified intake manifold with closed injector places and re routed water lines.

Now here people are not that much of help for NA builds and specially with RB26 head. I wanted to do with RB25 head as easier to get NA RB25 here but that adapator plate saved a lot of work so went with RB26 head.

First major issue coming is the engine compression now can anyone guide where and which pistons to get to increase the engine compression. I have seen people mentioning using RB25 pistons in RB30 blocks but with RB25 head here no clue.

Apart from tapping holes for the head studs and drilling for tensioner to fit the bigger belt is there anthing else required?

Last whats the best solution to run the ignition here either to go for something electronic or distributor style.

Edited by docaam
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... This is just, so much money for such little power. All I can say is good luck man

There's an NA 26 on here somewhere that looks pretty sweet, although I don't understand why you wouldn't just turbo the engine you're looking at putting in? Wouldn't hurt and it would go a lot better :)

I already have a turbo engine in the S30, but for me in this project its not about all power power thing, S30 chasis is very nippy even on stock 160hp engine. Wanted something old school style and true to its roots. I will be using the car while this engine is done, might take a while as need to order parts and paying huge shipping on each and everything but it will be worth in the end.

This inspired me

4497817305_e87cd2b4b0_o.jpg

I saw that thread before and even checked with utube videos, car is sick sounds amazing. Only issue is the guy did a lot of machine work and he changed few things according to his taste (sent him a pm).

I am more interested if someone can help in recommending part off the shelf, I cant trust mechanics here taking measurements like in the above quoted thread and then getting back to me to order the parts.

Will changing the pistons for compression would be enough

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Why not fuel injection? You are building an old 240Z!

There is a guy in NZ successfully running a 2wd n/a 2L skyline with individual throttles in Rallying and hillclimbs and he reckons he needs lots of revs to keep up.

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IBTs or Carbs will decide once engine had/block is complete an thats Im more worried about now what to get to complete it.

Its easier to run ITBs because of stock ITBs already there but as of now itch is more for carbs lol.

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No answers?

How much compression problem can be solved if I install RB25 piston in RB30 block to use with 26 head? as I read somewhere if the head is RB25 then compression goes upto 10 by using RB25 pistons. Will shaving 2mm head on top of that will give me enough compression to run a nice NA setup?

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You might have to machine the block to get the CR you want or get custom pistons. Ref Gerg - he knows what it takes.

I did message him but......

Anyways sold the RB26 head as was not getting some solution. So now the question is if I get RB25DE Neo head then there should be any compression issue? or still it will be there. As the two options Im looking now is to either use RB30 block with RB25DE head or just RB25DE Neo all together

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Geez, rip into the guys who want to build N/A engines...

A 3.0ltr N/A twin cam will go hard if you can get enough compression in it. You just have to look how well the old L series engine goes in the light Z shell to know that.

So I'm the guy from NZ who rally's the 2.0ltr N/A with ITB's. Quick note on what we did to get the compression up since hi-comp pistions for and RB20 are pretty much non existent. Like mentioned above, we machined the block to get the pistions proud when at TDC and also machined the raised edge off the outside of the pistions so they could come closer to the head.

To test clearance we bolted the head on with no gaskest and turned the moter over. My cams have a lot of lift, so we were pretty keen to make sure the valves cleared also.

This bumpped the compression nicely and mad the moter real responsive and lively. I rev it hard because it is only 2000cc, and I can't help myself! As you know the 3.0 will produce torque and you really should only need 7k.

We are pulling it down at the moment because we think we can go a bit further with these mods.There does seem to be a bit of space in there. Will be doing the old fashioned pasterscene on the piston durring the dummy up to get a measurement of clearance this time.

Good luck with the build, would love to buld one of these 30/25's with carbs!

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I love the idea of what you're trying to achieve, but one question. I have not worked with or had much experience with carbs. What advantages do you see from running a carb setup, seeing as the engine will be fuel injected to begin with?

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Geez, rip into the guys who want to build N/A engines...

A 3.0ltr N/A twin cam will go hard if you can get enough compression in it. You just have to look how well the old L series engine goes in the light Z shell to know that.

So I'm the guy from NZ who rally's the 2.0ltr N/A with ITB's. Quick note on what we did to get the compression up since hi-comp pistions for and RB20 are pretty much non existent. Like mentioned above, we machined the block to get the pistions proud when at TDC and also machined the raised edge off the outside of the pistions so they could come closer to the head.

To test clearance we bolted the head on with no gaskest and turned the moter over. My cams have a lot of lift, so we were pretty keen to make sure the valves cleared also.

This bumpped the compression nicely and mad the moter real responsive and lively. I rev it hard because it is only 2000cc, and I can't help myself! As you know the 3.0 will produce torque and you really should only need 7k.

We are pulling it down at the moment because we think we can go a bit further with these mods.There does seem to be a bit of space in there. Will be doing the old fashioned pasterscene on the piston durring the dummy up to get a measurement of clearance this time.

Good luck with the build, would love to buld one of these 30/25's with carbs!

Thanks for the reply, this is what I want to check, I also read RB25DE has flatter piston so shaving a bit of block and then pistons can work out something.

I will be using only stock parts as will built the engine down the road.

I love the idea of what you're trying to achieve, but one question. I have not worked with or had much experience with carbs. What advantages do you see from running a carb setup, seeing as the engine will be fuel injected to begin with?

if u dont trust the mechanics there dont let them fiddle with a high strung carb setup way to much to fiddle with and get right stick with the itb and injection it is a lot more reliable and will make better power

Carbs for the old school feel, I can install that on stocl L series engine but a twin cam engine would be better suited.

As I said earlier its not for a race car or something and I would be happy with 230-250hp but its just the sound and rawness of triple carbs on a twin cam head which is exciting. S30 is a very light car and I am running now RB25DET Neo its pretty nippy so power wont be an issue. According to what I have seen this setup which Im planning and a normal RB25DET in S30 both would be on par if taken on the track. NA will give a good low end torque and everything comes sudden.

Now for the question,

1. Will RB25DE S1 or S2 would be better or Neo? as Neo is half the price of old ones here and more inclined towards it because of in better condition and lifters are better.

2. Can anyone confirm if RB25NA piston fit easily in RB30 NA block and will help in getting the high compression Im looking for

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I'm going to assume you will get custom cams made up. To do it propperly you really need custom pistons... And if your going to get pistons made, then use a 26 head (because fitting side draft carbs will fitt better) then use any rb ignition set up with a stock ecu (that you can fitt a nistune board to).

If you arn't getting cams made, and you don't want to get pistons made. Use an r43 neo NA head, deck the block and machine down r34 neo N/A pistons to get enough valve clearance (or machine valve reliefs in the piston crown)

Either way you need 10:1 + static CR to get the best out of it using good fuel.

I have spent some time in your area and I think you may find it hard to find somone who can get the best out of a carbied set up (especially due to the heat, even in winter)... carbies are verry sensitive to everything.

To get the sound and look, I would still bolt side draft carbies on and still run fuel injection/sequential ignition. I have seen some pretty cool injector-in-carbie builds (to retain the look and sound, but deliver a much better fuel controll (cold and hot start, idle, accurate afr at all load and rpm etc etc).

Cheers

Justin

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Thanks Justin for the reply. You are right about carbs and jetting done here and running in summer I kept all this in my mind but still want to proceed with it. For the engine I want to built the engine change cams and pistons at later stage first just want it to run then take it from there.

Any details how to run carbs and injectors together.

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I'm running 25DE pistons that have been shaved, also had the block shaved and the head leveled I think from memory. When it was all said and done the compression ratio was over 12:1 which is so border line having to run race fuel (something higher than 98 - 100 octane at least anyway) that on a hot day here in Australia it would ping. I now run a 1.8mm steel multi layer drag style head gasket which has brought the compression just under 12:1.

I have spent almost 9 months in Dubai and it's not just hot, it's F**KING HOT!!! So here are a few little things that I see that might be a drama from the time that I have owned my 26/30, the carbs while they would make any RB lover moist in the crutch hearing them at 8000rpm+ probably aren't going to work very well with the humidity and the temperature that is in Dubai even when it get's 'cold' (less hot), you will also need someone that knows how to tune carbs and knows skyline motors well, because if something goes wrong it's going to go wrong in a big way, believe me and it gets expensive after a while.

Not trying to put a downer on anything, all the power to you for making a wicked N/a motor, I just don't think it's going to work very well where you are unfortunately.

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