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How Do I Raise The C/r To 9.0:1 ?

Turbo_Knuff

By Turbo_Knuff,
in Engines & Forced Induction

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The Dan Grand Master

The Dan

Posted
Posted

WTF? RB25DET's are factory 9:1 comp ratio

You are gaining nothing by putting RB26 gear in your RB25 block. Unless you have a spare crank lying around that you need to use. The stroke is slightly more but the extra 100cc is not going to do FA for torque or power.

Turbo_Knuff Enthusiast

Turbo_Knuff

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The reason I will use rb26 crank is because I have the block and enginehead but no crank,rods or pistons. So instead of buy an rb25 crank and then mount a crank collar on it would cost almost as much as an longnose rb26 crank. If 100cc doesn´t do anything then I wonder why so many high performance gt-rs from japan is stroked to 2,7?

Almost every aftermarkets pistons for rb26 is 8.5:1 but If the rb25 head is smaller cc maybe it is possible to get 9,0:1 then :)

R31Nismoid Grand Master

R31Nismoid

Posted
Posted

^ umm but how do you have a RB25 now, without any innards?

It's not even 100c, its like 60 or something.

9:1 will be fine, pretty standard for anyone rebuilding in this day an age considering fuel advancements over the past 10 years+

Also just use GTR rods, they are fine for over 400rwkw and less than half the price of eagles

Turbo_Knuff Enthusiast

Turbo_Knuff

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^ umm but how do you have a RB25 now, without any innards?

It's not even 100c, its like 60 or something.

9:1 will be fine, pretty standard for anyone rebuilding in this day an age considering fuel advancements over the past 10 years+

Also just use GTR rods, they are fine for over 400rwkw and less than half the price of eagles

I bought a head cheap for about 1 year ago. The I found a block now to. So I will use them to build a complete engine of. A std rb25det cost about 2300Aud here and Im gonna change so much anyway so I think this would be the best way to go :)

R31Nismoid Grand Master

R31Nismoid

Posted
Posted

You can buy a RB25 bottom end for next to nothing my friend... the head is the most expensive part.

Then just GTR rods ontop of that and you are set. Would be less than $1000 AUD easily. Not sure there you get 2300 from when you already have the top end :)

Beats buying a new RB26 crank IMO, unless you know the RB26 crank you are getting is fine but the cost to check, and if it needs repairing then its almost neutral.

Turbo_Knuff Enthusiast

Turbo_Knuff

Posted
  • Author
Posted (edited)
You can buy a RB25 bottom end for next to nothing my friend... the head is the most expensive part.

Then just GTR rods ontop of that and you are set. Would be less than $1000 AUD easily. Not sure there you get 2300 from when you already have the top end :)

Beats buying a new RB26 crank IMO, unless you know the RB26 crank you are getting is fine but the cost to check, and if it needs repairing then its almost neutral.

Im from Sweden and It´s alot more expensive with parts here. I have searched for a while for a bottom but didn´t find someting we don´t have so many parts here. So I had to order the block from England. I want the long oilpumpdrive to so I think the rb26 crank would be fine.

Edited by Turbo_Knuff
The Dan Grand Master

The Dan

Posted
Posted
Im from Sweden and It´s alot more expensive with parts here. I have searched for a while for a bottom but didn´t find someting we don´t have so many parts here. So I had to order the block from England. I want the long oilpumpdrive to so I think the rb26 crank would be fine.

The collar can be purchased and fitted for about $200 total. Being in Sweden might make things hard but there's always international shipping

James_03 Mentor

James_03

Posted
Posted (edited)

Don't think that getting a second hand rb26 long nose crank is the best solution, because IMO it's not.

Often times on a second hand crank you will see where the oil pump drive has rounded away on the edges of the flat even on the long nose. A collar with international shipping will be under $100AU easily, and then you know the drive is 100% OK after fitting.

Edited by James_03
The Dan Grand Master

The Dan

Posted
Posted
DO NOT shave the head more than just a surface because it'll stuff up your cam timing and possibly make the timing belt go slack.

Just order some custom 9.2:1 pistons. You won't be disappointed!

Sorry but that's the biggest load of shit I have ever heard. You aren't going to take enough off a cylinder head to have that much of an effect on the timing belt.

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