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Head Check

xsv_32

By xsv_32,
in General Automotive Discussion

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xsv_32 Enthusiast

xsv_32

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One of the first things i bought for rb30det project was the head. I bought a greddy replica intake plenum as i just cant afford the genuine item :(

It arrived and i put aside till i wanted to fit it. I went to bolt it up to the head but the 2 or 3 locating studs dont line up, by a long shot. There a 3 studs, the top front and rear and the third is one in the middle. If i pick one to line up the other either misses the hole or the stud goes into the plenum runner! its as if the plenum is too long for the head. Ive never heard of these plenums not lining up so i have to wonder if the head is actually a rb20 and ive been shafted royally.

Yet the high mount exhaust manifold lines up sweet, but is made for 25 heads only.

Please give me some advice>!!!

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frigjam Collaborator

frigjam

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RB20/25 exhaust side is identical, so that would line up regardless of what sort of head you had.

You may very well have a RB20 head, as the inlet manifolds are different and not interchangable..... Easiest way to tell would be check the combustion chamber on the head as RB20 block has a 78mm bore and RB25 is 86mm.

Hope that helps you mate.

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xsv_32 Enthusiast

xsv_32

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RB20/25 exhaust side is identical, so that would line up regardless of what sort of head you had.

You may very well have a RB20 head, as the inlet manifolds are different and not interchangable..... Easiest way to tell would be check the combustion chamber on the head as RB20 block has a 78mm bore and RB25 is 86mm.

Hope that helps you mate.

Umm measured the combustion diameters, 86mm. My workmate suggested there could be a difference between th s1 and s2 heads. Ive taken some photos but cant upload them jst yet. It also has the oil passage for the vct...

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  • 2 weeks later...
SideWaysChef Collaborator

SideWaysChef

Posted
Posted

i may be guessing but from memory a RB20 intake will not fit a RB25 head...think you might have a RB20 intake mate but I dont really have a way of proving this.

I just know I went to buy one of these cheapy aftermarket plenums and they only had ones to suit a RB25 so that would suggest the RB20 one is differant

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