R33 Rb30 Conversion

[Cubes]

You want a 0 deck clearance. At top dead center the piston is flush with the top of the block.

[Guilt-Toy]

i still can't really see any point to using forged pistons in a street car. but each to their own, the extra $600 or so for the build might help you sleep at night anyway, if so it's money well spent i reckon.

we'll see how long my casties last and what power i put down with them reliably anyway, might help some people see the light

p.s. had my first run with a fastish car on the weekend - "200rwkw" 180sx down the gold coast. anyway murdered him through 2nd and 3rd - even with the laggiest turbo known to man. i really need a tune too.

hey!

I got casties in my rb30 too. did you change the rod bolts at all? because mine are stock also.

How much power have you made ??

Mine was tuned to 16psi only because i am too scared of breaking the engine. if i was game id run it to 22psi and roll off another hundred hp at the rear wheels at least.. but yeah im scared of the cast comming to pieces or something lol

tell me the details of your engine ?? will be interesting for my next power up

[SirRacer]

You want a 0 deck clearance. At top dead center the piston is flush with the top of the block.

sounds good, you have been there done that so all the info is pretty helpfull

whats a formula to work out comp ratio and what ratio were your pistons ideally, had they been in an rb25

[StockyMcStock]

hey!

I got casties in my rb30 too. did you change the rod bolts at all? because mine are stock also.

How much power have you made ??

Mine was tuned to 16psi only because i am too scared of breaking the engine. if i was game id run it to 22psi and roll off another hundred hp at the rear wheels at least.. but yeah im scared of the cast comming to pieces or something lol

tell me the details of your engine ?? will be interesting for my next power up

No i didn't bother changing the rod bolts. Have you ever heard of rod bolts breaking on an RB30? cause i hadn't

i have only a vague idea of what power my engine is making as it's still running an RB25 base map for the time being. as i mentioned, it REALLY needs a tune. but i'm not going to bother yet, not until my blower is on the engine and piped up.

basically i have a built RB30DET with custom manifolds and a GT40 turbo with 1.34!!! rear housing at the moment. it was all built to run as a twincharge with an Eaton supercharger, hence why the rear housing on the turbo is so large. it's still remarkably good to drive though, even with RB25DE cams and no tune the top-end power is astounding.

[croat]

Just spent over an hour reading this thread.. tired as hell. sorry if i missed it but if the RB25/30 conversion is done, can a R33 gtst power FC tune it all up or do you have to go with another type of comp?

[88silhouette]

Just spent over an hour reading this thread.. tired as hell. sorry if i missed it but if the RB25/30 conversion is done, can a R33 gtst power FC tune it all up or do you have to go with another type of comp?

yeh mate i run gts-t pfc with my 30det

[N I B]

PFC will do it

[platinum]

got mine back yesterday, has a very mean "serious business" exhaust note haha.

No boost as yet until it's run in, but even so definatly has more balls than the n/a i drive daily.

Just itching to get some boost into it though.

[fatz]

head restrictors

does anyone have a pick of the hole i have to weld up and the the one i have to put the restirctor in

also when do i get one of these restrictors

pete

[Sydneykid]

head restrictors

does anyone have a pick of the hole i have to weld up and the the one i have to put the restirctor in

also when do i get one of these restrictors

pete

There are 2 oil feed galeries in the block that mate up to matching galleries in the head. They are between #2 & #3 and #4 & #5. Block the rear one and restrict the front one. A piece of brass rod drilled to the right size hole works well as a restrictor.

cheers

[mr_rbman]

got mine back yesterday, has a very mean "serious business" exhaust note haha.

No boost as yet until it's run in, but even so definatly has more balls than the n/a i drive daily.

Just itching to get some boost into it though.

good to hear gav, about time! Can't wait to see it!

[Spoolup]

Easier to tap the rear for a grub screw or put a solid piece of brass in to plug the hole - than to weld it up.

head restrictors

does anyone have a pick of the hole i have to weld up and the the one i have to put the restirctor in

also when do i get one of these restrictors

pete

[r33_racer]

Just a question regarding pistons and compression ratio stuff for this conversion. Cubes I think stated a page or so ago that the compression height for a rb30 normally was 1.26". Now the CP pistons for the conversion I got have a compression height according to the spec sheet of 1.28". So my understanding is that the piston will actually sit .020" (.5mm) outside of the bore when at TDC. Is that correct?

They reckon with a 1.2mm (.048") headgasket you should get about 8.3:1, now this worked out in my calcs if the head cc's up to about 64cc. If your head cc's up about 62cc then i think i worked it out to be about 8.5:1CR. I just want to check the formula here so hopefully im working this out right.

CR = 1pot vol+head cc+deck height cc / head cc+deck height cc

So if the piston sits .020" outta the bore then I should take that away from the headgasket thickness im running or plan on running and work it out from there...eg if i used a 1.5mm gasket, minus that .020" i would use 1mm in the equation to work out the CR, even though Im using a 1.5mm gasket.

Does that sound correct? Or have I confused myself here?

[Cubes]

I am not 100% sure what the std rb30 comp height is to achieve a zero deck clearance.

The best way to know what comp ratio you will have is to buy your pistons last. Measure everything up then select what pin height etc you require.

[r33_racer]

I checked acl website and for a set of forged pistons for rb30et they stated on their spec sheet that the compression height is 1.261"

Im assuming the forged piston is just a copy of the std one and maintains all std specs. So 1.26" is pretty close to std.

[Sydneykid]

Most of the pistons mentioned in this thread have different crown design/machining. Some are dished, some raised, some have small valve relief fly cuts, some have large ones. All of these affect the compression ratio.

Compression height is useless without knowing the dome cc's.

cheers

[fat200sx]

My rb30det conversion with an R34 NEO head, is a R31 wagon

[SirRacer]

Most of the pistons mentioned in this thread have different crown design/machining. Some are dished, some raised, some have small valve relief fly cuts, some have large ones. All of these affect the compression ratio.

Compression height is useless without knowing the dome cc's.

cheers

how do we take the dome cc's into account when measuring the compression ratio

how would using the rb25 pistons also affect them when the block is decked to suit?

[r33_racer]

The CP's im using have no dome in them..they are flat tops. So i dont believe that part is in my calculations.

[Cubes]

The discussion is piston selection for the rb30det.

First thing we need to do is select a suitable compression height which is 1.260". THEN we worry about the dome or negative done to achieve the comp ratio we are after.

Without a dome and zero deck clearance you will be running some where around a 7:1 comp ratio. :