Conversion: RB30DET vs TD42T

[KIWI]

I'm starting to get bits together for when I eventually do a conversion on my GU shorty (RD28 auto).
I can get the RB motors cheap enough over here, and I have found a TD42 with a Denco turbo kit fitted, but need to decide soon which I will go for.

I would prefer the TD, but it will be more involved, and will mean an extra $2000 on a GU gearbox, plus other bits, whereas the RB conversion is fairly straight foward.

I'm not after speed, just enough torque for off road, but I'm unfamiliar with the RB motors (will be fitted with RB25DET head) so want to make sure its not going to be the wrong decision if I go this way, especially when it come to using around water/mud.

Any advice is appreciated.



Cheers,
Dave

[brad-chevlux]

if you go with the RB30/25det leave the stock RB25 turbo on it, run about 8psi. pay attention to the compression ratio (you'll want about 9:1) and run it with a stock R33 skyline ECU.

It will fall on it's face at about 6200rpm, but will be on boost very low and will be very nice to drive.

one last thing, take the time to run the external oil feed for the VCT on the intake cam. it's worth the effort

one extra last thing. USE THE RB25DET OIL PUMP!!!!!!!!!

[KIWI]

Thanks for the info.
Is it worth running the 30 bottom end, or just stick with the 25?


Cheers,
Dave

[nellyb1]

i understand that there may be an issue with the oil and water jacket lines going from the 25 to the 30.

Or maybe its only an issue in the 30 -26 head conversion.

I'm looking at dropping out the tb42 and throwing in a 25det.

I've worked out power to weight and the stock skyline motor wil reduce it from around 15kg/hp to 9kg/hp. This is just going off the what the books say about the power and weight of the cars, so it may be way wrong.

If you think about it, the gearing will allow the engine to rev higher quicker, meaning that it will maintain boost better. Yeh if you need extra power going up and over something off road, you may need to rings it necka little bit, but with more power (once on boost) and better fuel eco,you'd have ot be happy.

Keep me posted on the change over and i'll do the same mate.

have fun.

[brad-chevlux]

Thanks for the info.
Is it worth running the 30 bottom end, or just stick with the 25?


Cheers,
Dave

It's very worth using the RB30 bottom end. low down torque is what you need in a patrol, the RB25 just doesn't have it.

If you go that way, i'm more then happy to help out with the engine build as much as you need. I've done a few now and they are a good thing.

[brad-chevlux]

i understand that there may be an issue with the oil and water jacket lines going from the 25 to the 30.

Or maybe its only an issue in the 30 -26 head conversion.

the oil feed for the VCT in the RB25 head lines up nicely with the water jacket in the rb30 block. the oil feed in the head is welded over, the RB30 head gasket is used as a guide for welding and the the water port in the head is opened up slightly to better line up with the head.

A hole is drilled and tapped with a 1/8 NPT thread in the side of the head into the oil passage for the VCT, you then use a 'T' adapter to take oil from the oil pressure sender to the head.

OR

you can weld up the head and use an RB20 intake cam and gear and not use the VCT.


the block also needs some minor 'clearencing' for the RB25 exhaust manifold to fit.