Budget Rb30 - Neo Head Build Advice

[dave1200]

Hey Guys I haven't been on here for a while and just wanted some advice about my plan;

I've got a healthy R31 silhouette manual that I wanted to throw a twin cam head on.

My plan is to buy a complete Neo motor with all sensors ecu etc. Bolt the head onto the RB30 block and ride off into the sunset.

-Use everything from the neo motor except the bottom end

-Fix the vct oil feed issue as is well documented

The Questions I've got are;

1. Will I have issues with the RB30 pistons clearing the twin cam head? (valve recesses etc?)

2. I'll end up with a higher compression ratio which is ideal but will it be excessive?

3. What have I forgotten?

I am quite competent doing heads/timing gear/ welding/ machining etc so am not afraid of the process but thought you guys could point out some glaring pitfalls I have missed?

Thanks - DAVE

[Ben C34]

Neo head and rb30 head have very similar combustion chamber volume, so no worries there, and definitely works with stock rb30 pistons so no worries either

Do it

[Dale FZ1]

Assuming you are sizing the turbocharger to suit capacity increase, injectors ECU etc. And put a RB25 spec oil pump on the bottom end plus a crank collar to get full drive engagement on the pump.

There haven't been any reported difficulties running stock 30E pistons with the Neo head, although diligence should dictate that you measure up to ensure nothing clashes.

Static CR shouldn't be through the roof considering the R33 spec head achieves in the 8.3-8.4 range with a very light facing of block and head.

[dave1200]

Thanks for the reply guys.

What's the purpose of the oil pump swap? I didn't plan on going turbo initially but if you aren't running oil squirters where does the additional need for oil come from? Since it seems cheapest to buy the full motor I could definitely steal the oil pump off the RB25 but I was hoping to leave the RB30 pump in place.

[KiwiRS4T]

If you're not going fully balanced 8000rpm I believe people do keep the stock bottom end including pump without drama. You would need the Neo ecu and loom and probably nistune the ecu. If you can keep the neo block intact there should be a market for it.

Some people have literally bolted the new head on with the minimum mods to make it work but I think most people strip the block and do rings and bearings (and preferably little end bolts with line boring).

[Dylan andrew]

The combustion chamber is a little bigger wouldn't have any problems there.

[Hunky]

Leave oil pump as is, and shim the pressure relief valve with a couple of washers ( I used 2 6mm spring washers and my pressure is 4 bar on start up and about 2-3 once running), if I was to do it again I would probably put 3 washer in maybe 4.

[dave1200]

Great thanks guys. This is going to be easy......haha

[Gillyr33gtst]

If budget is a issue consider hypatec pistons they come in standard pin hight and also .020 down so if your deck is rough all is not lost I just built my rb30det neo using them with 8:3 comp

[dave1200]

Cool thanks for the advice. At this stage I'm hoping the bottom end of the donor car will be healthy enough. I figure that since it's an N/A build it should be ok since it won't see the stress of a boosted version.

I've finished rebuilding the head and making all the oil supply and drain mods.

Next job is to start hacking up the wiring loom to remove extra wiring plus integrating with the R31. Should be some head scratching going on!

I should be clear, I'm not building on a budget. I am challenging the idea of how cheaply can you build one of these motors?

At this stage it's looking like I should be able to get the R31 running on a neo head with R34 n/a ecu for about $1100 all up.

[Gillyr33gtst]

Good work mate $1100 rb30de very cheap should go pretty well to hopefully the donor engine is in good order should post results once running

[dave1200]

yeah will do. I'd be happy if it made a good torquey 125rwkw. I imagine it'd be a bit of fun like that.

[KiwiRS4T]

I think you'll need the ecu nistuned and reckon you'll crack 150kw atw

[dave1200]

I've given this a bit of thought and it really should run OK on the standard ecu. I'm not going to go near the afm resolution limit, the 270 cc injectors will flow plenty. The only issue I can see is that it will be accessing load points in the map that the rb25 was not supposed to see. Knowing Nissan tuning it will result in a rich top end. You're probably right that if I added a nistune I could pull fuel out of the top end and free up a few more killer wasps.

[dave1200]

Can anybody help me out with a wiring/ecu question? What will the Neo ecu do with no knock sensors connected? Will it think there's no knock and run as normal or will it spit the dummy and go into limp mode? The reason I ask is because the knock sensor loom is not in the engine loom and I had planned to leave all r31 loom on the lower half of the motor. I've already stripped and rewired the engine loom and I spotted this afterward.... Derr

[iruvyouskyrine]

Will run knock maps. You can just put a 110kohm resistor inline for each knock sensor and it will run fine.

[dave1200]

Awesome thanks for the quick reply. I do plan to add the knock sensor loom into my chopped down engine loom but just forgot so it's good to have an option.

Is there any other items in that loom that may be crucial to getting the ecu running as per normal? Oil pressure sender? any of the alternator wiring?

[iruvyouskyrine]

Altenator, injectors, coilpacks, CAS, AFM, TPS should be enough to get it running. You need to get the bosses on the RB30 block machined if you want to use knock sensors. The provisions are there on all of them but only turbo blocks actually had a hole drilled and tapped.

[dave1200]

When you say machined, they are just a blind hole in the block on a small spot face right? If so can't I just drill and tap to the correct depth? If I had to I could probably throw it up on the mill but would have thought as long as you can get your pilot drill started you should be able to step up the hole carefully to the tap pilot size. I'm guessing they are a 1/8 or 1/4" BSP parrallel so should be right?

Can you see any benefit in reusing 1 of the knock sensors in the centre location in the RB30 block and then running the resistor on the other?

Yeah I've got all the other sensors/connectors sorted via resurrecting the ECM/COIL relay as well as the couple of items on the IGN relay.

[iruvyouskyrine]

Yes you can just drill and tap. I got my tensioner hole done at a machine shop so I just got them to do the knock sensor bosses as well.

I would drill and tap the two knock sensors and run both personally. It's pretty easy to get them both working and could be a huge advantage.