Jump to content
SAU Community

Recommended Posts

as title states guys

i have a RB25 block i have got back from the Machinest it has had all the usual rebuilt work done.

I am just after some info on cleaning up the casting dags ect inside the block. Whats the best way to aproach it?

and what should i not do ?

also i have an RB26 head and i am fitting it on the RB25 block. Using RB 25 crank and pistons. have other people done this sucessfully? how did the compression ratios turn out... as far as i calculated it was somwhere near 8.2 to 1.

cheers guys.

PS im using a 26 head because it was on my last motor and has port work and 272 10.5mm cams fitted. also the 25 block and crank was free.

Link to comment
https://www.sau.com.au/forums/topic/405240-rb-25-block-prep-before-assembly/
Share on other sites

Why not use rb26 crank and pistons to get the proper compression ratio. 8.2:1 is a tad low.

Rb25 and rb26 rods are the same, although rb26 are stronger.

Don't bother cleaning up any casting marks inside the block. Make sure all the oil and water galleries are free of swarf.

Inspect and replace welsh plugs.

What machine work did you have done?

Rb25 and rb26 rods are the same, although rb26 are stronger.

How can they be the same if the other is stronger? :P

Why not use rb26 crank and pistons to get the proper compression ratio. 8.2:1 is a tad low.

Agreed on the comp ration. 8.2 is quite low nowadays considering the quality of fuels available compared to 10 years ago.

Then add in 272 cams and depending on what port work, it'll be pretty unimpressive anywhere that isn't smack on the boost happy area.

Can use a RB25 crank though, and 26 rods. Not a major issue, just need pistons to suit then.

okies cheers guys i have removed the plugs. and i will fit new ones. i have oil restrictors aswell and a couple of plugs for the vct squirter and one of the oil squirters.

What machine work did you have done?

I got the block bored and torqu plate honed to piston specs

Line honed with cradle torqued with arp mains

Crank polished ballenced with clutch harmonic ballencer and flywheel. also taped the oil bungs in the crank and tapered the oil outlets on the mains and big ends journals.

The machine shop rebuilt the head with new valves jun valve springs and bronze valve guides and skimed the deck.

Machine shop also checked the CP pistons and Argo rods for weight and tollerences ect.

I do need a bit of help in reguards to my compression ratio. I dont understand how to work out the piston height above the deck or the CCs of the piston dome.

Please refer to the spec sheet supplied.

Stats of motor

Combustion Chainbor 69cc (Stock RB26)

RB25 Stroke 71.7mm (stock)

Bore 3.406in

Head Gasket bore 87mm

Head gasket 1.2mm Tomei

6itlr.jpg

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • just an update to this, poor man pays twice  Tried sanding down the pulleys but it didnt do the trick. Chucked another second hand alternator in the na car which I got for free off my mate and its fixed the squelling. Must have been unlucky with the bearings.    As for my turbo car, I managed to pick up a cwc rb alternator conversion bracket + LS alternator for 250 off marketplace, looked to be in really good nick. Installed it , started the car and its not charging the battery.... ( Im not good with auto elec stuff so im not sure if this was all I needed to do but I verified such by using a multimeter on the battery when the engine was running and I was only getting 12.2v )   I had to modify the earth strap for the new LS alternator , factory earth strap was a 10mm bolt which did not fit the bolt on the LS alternator which was double the size so I cut it off , went to repco bought some ring terminals that fit, crimped it onto the old earth strap and bolted it up to the alternator , started the car and same issue. Ran like shit and was reading 12.2 at the battery.  For a "plug and play" advertised kit thats not very plug and play but alas.  My question is , am I missing something ? Ive been reading that some people recommend upgrading the stock 80 amp alternator fuse to a 140 amp but I dont see how that would stop the alternator charging especially at idle not under load.  Regardless ive pulled it out and am going to get it bench tested by an auto elec tomorrow but it would be handy to know if ive missed something silly or have done something wrong.   
    • My wild guess is that you have popped off an intake pipe....check all of the hoses between the turbo and the throttle for splits or loose clamps.
    • Awesome, thanks for sharing!
    • To provide more specific help, more information is needed. What Android screen? What is its wiring diagram? Does the car's wiring have power at any required BAT and ACC wires, and is the loom's earth good?
    • So, now all you need to do is connect the 2 or 3x 12v feeds into the unit to permanent 12v, ACC 12V and IGN 12V that you can find in the spot behind the stereo, and the earth, and then it will switch on with the car.
×
×
  • Create New...