Rb25 Vs. Rb26 Design

[WizardBlack]

Hello,

I am looking at dropping a S2 RB25DET into my Datsun 280Z. I am wondering about the entire buildup process and have been collecting a lot of information. One thing I cannot seem to find is the actual, physical design difference between RB25 valvetrain and RB26 valvetrain. I understand if they have different springs and whatnot, but from everything I have seen, they are both shim over bucket and therefore equal in design? I know RB26 cams do not cross with 20/25. What am I missing? Are the dimensions merely different? Anyone have a photo of the valvetrain of 25 vs. 26? I like the idea of the RB's rev-ability and want to know how the 25 is rated compared to the 26.

Thanks,

Mark from Ohio

[Bunta]

26 has solid lifters and RB25 has hydraulic, thats the main difference. When you switch a 25 over to solid lifters there is next to no difference between the two, pm fineline on these boards if you want to know all the details, he got that all done and now runs 26 poncams in his 25 head. And in regard to revability the solid head will rev more as it wont have hydrailic lifters 'pumping up'

[WizardBlack]

  Bunta said:

26 has solid lifters and RB25 has hydraulic, thats the main difference. When you switch a 25 over to solid lifters there is next to no difference between the two, pm fineline on these boards if you want to know all the details, he got that all done and now runs 26 poncams in his 25 head. And in regard to revability the solid head will rev more as it wont have hydrailic lifters 'pumping up'

OK, now I am well and truly confused. Aren't the cam lobes riding right on top of the bucket/retainer/valve? Kinda like Subaru STi's? Where are the lifters at?

[Bunta]

if you can get the r33 workshop manual it has a really good expolded view of both the heads, it is readily available for down load, its kind of a bit hard to explain and im at work so i cant download the pictures myself!

[wolverine]

RB25DET neo have solid lifters

[brother_david]

In the RB26 head seen from the cylinder up; first the valve, then the vavle spring around it, sitting on top of the valve is a shim for the correct clearance, on top of that the lifter to take the hit from the cam knuckle Very straight forward, standard design.

In the RB25 you've got the hydralic lifters with all-in one-design instead

BTW the rb25 have got smaller diameter valves, guess you know this already!

[WizardBlack]

  brother_david said:

In the RB26 head seen from the cylinder up; first the valve, then the vavle spring around it, sitting on top of the valve is a shim for the correct clearance, on top of that the lifter to take the hit from the cam knuckle Very straight forward, standard design.

In the RB25 you've got the hydralic lifters with all-in one-design instead

BTW the rb25 have got smaller diameter valves, guess you know this already!

Oh, so the 25 does not have a bucket, but rather a lifter that is axially inline with the valve. I take it there's no way to change to the bucket design short of buying a 26 head?

[WizardBlack]

I found the manual. Thank you. I think I see how they are different. I've never seen a hydro lifter of such design. I guess you get the benefit of hydro lash adjustment without the possibility of spitting a rocker or adding undue weight to the valvetrain.