rb25 head versus rb26 head (valves, springs...etc)

[Varchild]

Hi, this is my first post here!

Also, I did search this and other places but couldn't find this answer.

 

So here's the question:

Aside from solid lifters vs hydraulic what differences are there between the rb25 and 26 heads? different valves? different springs? are the valves sizes the same? Port sizes?

 

Thanks!

[Careless]

• different spring-rate, but I've read of people using GTR springs in RB25 motors.

 

• valves are sodium filled on exhaust side.

 

• RB25 head has VCT in some cases, which is variable cam timing. It's identifiable by the VCT Solenoid Connector that is in line with the head of the cam at the front/side of the head

 

• That means the cams are different.

 

• 11mm head bolt for 25, 12mm head bolt for 26.

 

There are some FSM's floating around that have the information for the 20, 25, and 26, and there is also the head spec portion of said FSM. They will tell you the valve head diameter and spring pressure.

 

I believe the ports are much better shaped in the 26, and only require reshaping the bowls, and smoothening the exhausts to be a very high flowing head, just short of enlarging everything.

 

Sounds like you want to build an RB30 block.

[Varchild]

Thanks, that's great info. Right now I'm just researching possibilities for a future project rb swap and I just like to know details.

[Guest Momentum is critical]

Hi,

I saw on the Ferrea Racing Components site, valve stems for sale for rb26 and rb25 showing the stock stem size's, I thought it mite help

 

http://www.ferrea.com/general-results.php?company_id=100631&category_id=6078