Jump to content
SAU Community

Recommended Posts

(edit)

Head is off. Bores measured at close to 83mm. Bores seem to be in quite good condition.

Please any of the RB guru's I'm looking for any recommendations for the rebuild to suit drift applications with regular street use.. The engine was run with no oil to the extent of the exhaust cam ceasing.

At this stage I'm looking at-

Fresh rebuilt stock de-burred head

Retaining the east bear 1.8mm HG

Power enterprises F1 black metal bottom end bearings

100k service kit

Rear oil seal

Oil restricter/s (what size/type?)

Bolts/studs - which of these need replacing?

Edited by Drift_Limo
Link to comment
https://www.sau.com.au/forums/topic/174226-rb20-not-sure-anymore/
Share on other sites

seriously why would u want to? I mean the cyliners are 78mm vs the 86mm (or something way off as im not familiar with rb25 specs)

The cylinder size difference, let alone the valve sizing (29 vs 36?) would be enough to make anyone not want to do it. Boost is a measure of resistance to airflow so if u have smaller ports/valves then u need to cram more air in (more boost) to get the same number as u would using a 25 head.

If i were u id be slapping the 25 head on and enjoy a lower boost level for the same power u had before.

Cubes and i had our heads mildly ported before doing the 3lt and i can tell u we dont have to push as much air in as some to make some good power.

Well I'm hoping for 82mm Tomei pistons, which should mean a full RB24 kit..? Will be pulling down the bottom end in the next few days. What is the easiest way to identify RB26 rods and crank?

Was a big surprise, as the auction details from j-spec said the car was fitted with an RB25 engine and transmission!

Edited by Drift_Limo
Boost is a measure of resistance to airflow so if u have smaller ports/valves then u need to cram more air in (more boost) to get the same number as u would using a 25 head.

But something to remember. Is whilst you say small valves, for the 2L displacement they are not a abd thing. Consider the swept volume of each cylinder, then compare it to the surface area of inlet valve and then exhaust valve. The ratio of valve area to displacement for an RB20 is better then an SR20, and not far off an RB26. When you consider the valve size of an RB25/26 head on an RB30 bottom end then the ratio is worse then it is on an RB20, its about the same as the SR20.

So obviouly more displacement and valve area means more power...but looking at it in isolation as a ratio, the valves in the RB20 arent really small for their application.

but looking at it in isolation as a ratio, the valves in the RB20 arent really small for their application.

Are the 20 valves undersized for the 25 though...? An extra 25% of displacement would mean a need for larger valves. I dont see any advantage of running a 20t head on a 2.5 or 3lt block, but ppl still think its a good idea?

Why do u need custom 86mm pistons ? :(

Also I got an RB20 in car right now. I also got and RB24S seating in the garage. I was thinking about putting a 25DE/DET head on and turboing it.

Hmmm, but it wasn't really rev happy before. Like 6000rpm redline. Don't know if the head and electronic fuel/ignition management would help with higher redline :)http://www.answers.com/topic/nissan-rb-engine

Thanks! ))

Ok will measure stroke tomorrow, also dropping the sump and have a mechanic friend inspecting what bearings will need replacing.

Will Nismo bearings suit my application? RB20 or RB26 bearings?

What bolts should be replaced?

Edited by Drift_Limo

Throw King bimetals at it.

There's a lot of highpowered rb25/26 and 30's getting around with absolutely no issues.

They are a tad more expensive but worth it.

http://www.kingbearings.com/

As its a stroker of sorts it you may be worth while picking up a set of cheap gtr cams for $50-$100 and have Tighe Cams in QLD regrind them for a hair over $200 a pair.

You get around 8.5mm lift and 252-254 duration. So nice and mild.

Well the pistons are cast and seem to be of Nissan origin. Only visible markings on them were '08U'

Crown to deck height was around 53.5mm (ruler measurement so not exact on this)

Markings on rods were 20-3 05U41-1

Crank '08U'

Edited by Drift_Limo
Throw King bimetals at it.

There's a lot of highpowered rb25/26 and 30's getting around with absolutely no issues.

They are a tad more expensive but worth it.

http://www.kingbearings.com/

As its a stroker of sorts it you may be worth while picking up a set of cheap gtr cams for $50-$100 and have Tighe Cams in QLD regrind them for a hair over $200 a pair.

You get around 8.5mm lift and 252-254 duration. So nice and mild.

Hi

I can also confirm that.

KING's make some quallity parts, and your right in saying there is a lot of RB's running them with huge power.

Very popular with the Rb30s, I had them in my forged RB30 bottom end and they were fine! Available at a good price from VPW, Melbourne.

Good luck with the project.

Thanks,

Abu

83mm bores with std pistons??????? Strange, perhaps they are the Toyota pistons that ppl speak of being able to use?!?!?!

An option, maybe havent considered....

If you are going to be retaining the 2530 you run (memory?) then i would grab a std short motor and just rebuild your head in your own time. Maybe play with porting and some cheap cam grinds then when the heads ready throw it on and retune with new head gasket. The std bottom end will put up with the power ad boost you will run with a 2530

Cars that only owe you 2k to get back to the track are far more fun then ones that cost far more to repair and keep you away from the track

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

    • I've got the rear ones, they're certainly beefy. I need to take them to my driveshaft guru to check over, he's very fussy about the quality of components so I'll let you know if they are made of cheese by a blind man.   Are you in Australia? A mate just had a set of EN26 shafts made for his K20 Lotus by our fabricator which were quite cheap (compared to Driveshaft Shop) so if you can procure the CV's and draw what you need he'd make them for ~$800 for the pair.
    • Had I known the diff between R32 and R33 suspension I would have R33 suspension. That ship has sailed so I'm doing my best to replicate a drop spindle without spending $4k on a Billet one.
    • OEM suspension starts to bind as soon as the car gets away from stock height. I locked in the caster and camber before cutting off the kingpin. I then let the upright down in a natural (unbound) state before re-attaching it. Now it moves freely in bump and droop relative to the new ride height. My plan is to add GKTech arms before the car is finished so I can dial camber and caster further. It will be fine. This isn't rocket science. Caster looks good, camber is good, upper arm doesn't cause crazy gain and it is now closer to the stock angle and bump steer checks out. Send it.
    • Pay careful attention to the kinematics of that upper arm. The bloody things don't work properly even on a normal stock height R32. Nissan really screwed the pooch on that one. The fixes have included changing the hole locations on the bracket to change the angle of the inner pivot (which was fairly successful but usually makes it impossible to install or remove the arm without unbolting the bracket from the tower, which sucks) and various swivelling upper arm designs. ALL the swivelling upper arm designs that look like a capital I (with serifs) suck. All of them. Some of them are in fact terribly unsafe. Even the best one of them (the old UAS design) shat itself in short order on my car. The only upper arm that works as advertised and is pretty safe is the GKTech one. But it is high maintenance on a street car. I'm guessing that a 600HP car as (stupidly, IMO) low as you are going is not going to be a regular driver. So the maintenance issues on suspension parts are probably not going to be a problem. But you really must make sure that however your fairly drastically modded suspension ends up, that the upper arms swing through an arc that wants to keep the inner and outer bolts parallel. If the outer end travels through an arc that makes that end's bolt want to skew away from parallel with the inner bolt, you will build up enormous binding and compressing forces in the bushes, chew them out and hate life. The suspension compliance can actually be dominated by the bush binding, not the spring rate! It may be the case that even something like the GKTech arm won't work if your suspension kinematics become too weird, courtesy of all the cut and shut going on. Although you at least say there's no binding now, so maybe you're OK. Seeing as you're in the build phase, you could consider using R33/4 type upper arms (either that actual arm, OEM or aftermarket) or any similar wishbone designed to suit your available space, so alleviate the silliness of the R32 design. Then you can locate your inner pivots to provide the correct kinematics (camber gain on compression, etc).
    • The frontend wouldn't go low enough because the coilover was max low and the upper control arm would collapse into itself and potentially bottom out in the strut tower. I made a brace and cut off the kingpin and then moved the upright down 1.25" and welded. i still have to finish but this gives an idea. Now I can have a normal 3.25" of shock travel and things aren't binding. I'm also dropping the lower arm and tie rod 1.25".
×
×
  • Create New...