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Rb25de Replacement Pistons

Dale FZ1

By Dale FZ1,
in Engines & Forced Induction

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Dale FZ1 Veteran

Dale FZ1

Posted
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I've got to replace a piston that's seen contact with a foreign body (screw) that was dropped into the combustion chamber. It seems that genuine Nissan is the only option. I don't want/need the forged low(er) 9:1 and 8.5:1 compression items offered for the 25DET.

A lengthy search of the SAU forum hasn't come up with any other information. Do any of you guys who've actually replaced pistons have ideas and/or sources for the 10:1 DE spec items?

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https://www.sau.com.au/forums/topic/202700-rb25de-replacement-pistons/
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Dale FZ1 Veteran

Dale FZ1

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I didn't expect to find forged slugs available, but felt there may have been a market for cast replacement 25DE.

Nissan do them, available ex Japan. Going rate seems around $110.

Anybody else with experience here who can tip in their knowledge please?

I've seen the general design used by BMW in the S50 I6 engine they used, and wondered if the piston design matches that of the RB. Combustion chamber and bore size is essentially the same - a German Nissan?? :(

H@ME Mentor

H@ME

Posted
Posted

Hey there dale, glad to hear the build of my old engine is coming along, i recieved your e-mail. i will have to get back to you later as it seems the hotmail server is down. gl n speak soon, hame.

Eug Grand Master

Eug

Posted
Posted

i've got a small write up at home somewhere saying that VG pistons fit, and bump up the compression a bit. i'll try to find it

alternative is buy a second hand set and have them rebalanced

or even RB30 ones.

Dale FZ1 Veteran

Dale FZ1

Posted
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I'd be interested to see the write up and get an idea of what's involved.

Specs sheets from ACL shows the VG30DE has a 87mm bore (+1mm on the RB), and different gudgeon height and diameter. That engine spec shows a 10.5:1 compression.

Looking at the 25DE piston, it appears that it achieves the lift from 9:1 (of the 25DET) to 10:1 compression by an extra couple of mm on the height of the crown, gauging by the valve relief cut outs that the 25DET forgies typically don't seem to have.

Perhaps someone with pics of the different pistons can post some up. I will get one of the 25DE to start it.

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