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Hey guys,

I have a S1 R33 with a S1 RB25DET. Recently I did a compression test on it and it says low on compression. So I bought another 25 head which I plan to swap over.

However upon taking it to a Head Shop today, they have stated the head may be a NEO 25. On the exhaust side of this head it says 5L83 and I'm just wondering if anyone can confirm this is indeed a NEO?

Also, is this going to now not be compatible with my S1 RB25 block? Just because this new head is straight and in good condition.

Cheers for any help!

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wouldn't it be easy to tell if its solid lifters or not ben?? they have smaller runners too don't they, wonder what the difference is there....

The runner size difference is minimal, unless its the na head, which is noticeably smaller.

The lifters are pretty obvious but the vct allen head grub screw rather than bolts and lack of vct oil drain on the side of the head is obvious from a distance.

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Yes it is a NEO head. The coilpack bolts straight onto the head in the NEO as with the non NEO engines are mounted on a bracket which are then bolted on by 12mm bolts.

Correct. This is how I was able to tell.

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