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Rb25det Neo Head With Rb26 Crank. Piston Options?

John M

By John M,
in R Series (R30, R31, R32, R33, R34)

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John M Apprentice

John M

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Hello,

Ive got an R34 RB25DET Neo motor, i put an R33 RB26DETT Crank & rods in it, and need help with piston selection.

The neo head has a CC of 51.5 which is smaller than the standard rb25, and way smaller than the rb26.

I bought rb26 pistons (87mm bore which my block has been bored out to) and after installing them, did compression ratio calculations and am getting something around 11:1.

Just wondering if anyone has some insight on this!

Thanks guys,

John m

Raleigh, North carolina, USA (S14 RB25 Neo)

John M Apprentice

John M

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what head gasket? and put up ypur calculations and someone will show you

Cylinder Bore Size 87

Piston Stroke Length 73.7

Head Gasket Bore Diameter 88


Compressed Head Gasket Thickness 1.2


Combustion Chamber Volume In CCs 51.5


Piston Dome Volume In CCs Negative For Dished Pistons (Use '-') 15.5


Piston Deck Clearance Negative If ABOVE Deck (Use '-') : -0.5715

(when using 87mm rb26 8.5:1 cp piston with Compression height of 1.193)

right now its at 11.9:1

I think im pretty much screwed on the Neo head + RB26 crank & piston combo. I thnk ill have to either

A. sell the neo head and go for the larger CC standard rb25 head

B. sell the whole built short block and get a bone stock neo bottom end and throw my neo head on it.

Opinions? help?

-Thx

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