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I have purchased a GT35R (0.82 exh housing) rated at 700hp.

The RB25DET head has the standard valve springs and valves in it.

There's no doubt the head will need new valve springs but what LBS should i be looking for?.

I intended to get all the power I can from turbo, would the head benefit from porting and to what extent would it need?, before fitting the new valve springs.

Keep in mind that the standard cams will be replaced with aftermarket ones later on along with adj cam gears.

Anyone know some good places for head work in the gold coast/brisbane area?

Hi Jaws, You are no doubt aware that RB25's have hydraulic followers and that you would be limited to ~256 degree cams with ~9.2 mm lift to retain the VVT. This means no change in valve springs is neccessary. If you wanted to run cams with larger lift or longer duration (therebye loosing the VVT) then you need a change to solid followers (as in GTR's). This should be done at the same time as the head is off. It is also worth noting that if you want more than ~9.5 mm lift, some very minor machining of the head (to clear the lobes) is also necessary.

As for porting, polishing of combustion chambers and matching combustion chamber volume it is always worthwhile doing while the head is off. :rofl:

Hope that is of some help :D

  • 2 weeks later...

Guilt Toy

Bonnet definately wont close on an r33. I know a mechanic in Newcastle who has done 3 of these conversions to r33's and he buys a custom made plenum everytime to solve the prob. If you want his number pm me.

Does anybody know why my r32 rb2530 will cut out sometime at the top of the rev range in third gear. Im assuming I have maxed out the afm, but does anyone know what the built in cut outs/defenders are and how they feel. Mine will cut all ignition to the motor until i remove my foot from the accelerator, it will just coast, then it goes again as if nothing happened.

Any ideas and how it can be overcome are appreciated.

Grey

Hi,

I couldn't close my bonnet with the standard setup and Rb30 conversion. I probably could have but didn't try forcing it. I didn't want to disturb the hood liner let alone the bonnet with the natural engine movement.

Doing the mods to lower the engine is quite straightforward...i.e. cheap.

You dont need to modify plenums or anything that drastic. You simply get a 10mm plate that sits between each mount and engine. The plate has eight holes. Four countersunk in the standard position to bolt the plate to the block, and 4 threaded, about 25mm lower to bolt the mount to the plate. Then you extend the mount slots on the crossmember as the mounts will naturally stick out a bit further due to the plate width. Remember to also trim the radiator shroud slightly to allow for the slightly lower position of the fan. The engine to gearbox braces also need minor relieving to clear some lines. Its all quite simple and easy, and will not look obvious.

GreySky,

I get a AFM cut around 5000-5500rpm when running over 16psi of boost on the stocker turbo with the RB20t.

It literally kills everything and scares the crap out of you the first couple of times it happens. First time it happened I thought I majorly stuffed something is it is a very harsh cut out.

The cooler it is the easier or earlier (psi) the afm cut will occur.

The most boost I can run on a cold morning/night is around 14psi, ~15psi and she will cut generally if winding out third, 16psi will cut during second etc.

Only way around it is either a fuel cut defended (which is dodgy if you don't check the car on the dyno after installing) or get the ECU tuned/powerfc. If you are still maxing out the afm after the ecu/powerfc then you will need the Z32 or Q45 afm as they output a lower voltage for a given airflow.

Phantom,

As you have lowered the engine a little has this introduced any vibrations or extra wear on the universal joints tail shafts center bearing?

Bit like the ol' VN/VS. VN's where pretty bad aligned, VS's wern't to bad but I still went through a center bearing after 50,000km's.

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