Jump to content
SAU Community

Rb30 Crank At Rb26 Block

Supra2000

By Supra2000,
in Engines & Forced Induction

 Share

Recommended Posts

  • 2 weeks later...
Supra2000 Contributor

Supra2000

Posted
  • Author
Posted

My friend

if I use RB20 Crank at RB26 block what will happen is any one tried, As you know the conrods is short and I think it will give me high RPM but the problem with stroke is low.

Please I need your advice.

mark99 Contributor

mark99

Posted
Posted
Have a look about 6 months ago.

Guy did it, wouldnt go into much detail so its safe to assume one of two things

1. He was talking shit

2. Is cost a lot of time, and money and probably isnt worth the effort

Plus, when a 26 crank works just fine, not sure why you would bother

1. i wasn't talking shit

2. It took a fair bit of time, i was looking at trying to see if i could do it and have it commercially viable, and for me it was worth the effort.

The reason to not just use a 26 crank, is because almost with out exception no matter what your application, more capacity will be better.

I did it by offset grinding the rod journals down from rb30 size to rb26 size, taking a little bit of stroke out as i went down. Final stroke was 83.2mm. i used standard length Eagle rb26 rods, i rebushed them to 22mm gudgeon pin size (but you can leave them at 21mm pin if desired) . Then used custom forged pistons. Yes the rod to stroke ratio ends up fairly poor. But it doesn't seem to to have any serious adverse effects on the engine. The car has low mounts, runs pulp, 18psi, makes 406rwkw, pulls hard from 4000, and pulls harder than an under sexed school kid from 5000 through to 8800. The engine revs freely and smoothly, and is sweet all the way through to the just short of 9000rpm rev limit. There is also counter weight modification required.

Ill be the first to admit, a longer rod to stroke ratio is better, and the the OS is an awesome bit of gear. But for me it was just time, so it was certainly worth it, who wouldn't want 2.9L? It worked out that i can do the cranks finished ready to go for $2500 dollars, this is nitrided, and with a crank collar fitted. Standard rods will not clear the block, so you need an aftermarket rod like an eagle or crower, and then of course custom pistons. So all up it works out a lttle cheaper than say an HKS stage 1 kit, but most people like brand names, so i've only had a little interest.

Hope that helps, feel free to ask any questions.

skybarge Community Regular

skybarge

Posted
Posted
My friend

if I use RB20 Crank at RB26 block what will happen is any one tried, As you know the conrods is short and I think it will give me high RPM but the problem with stroke is low.

Please I need your advice.

instead of using an RB20 crank, use 2x SR20det cranks, cut one cylinder off each and weld them together, it'll allow you to rev upto round 13000rpm...

Supra2000 Contributor

Supra2000

Posted
  • Author
Posted
instead of using an RB20 crank, use 2x SR20det cranks, cut one cylinder off each and weld them together, it'll allow you to rev upto round 13000rpm...

how I can cut the cylinder and make it who can make it properly it will not fit will.

Shane_954 Enthusiast

Shane_954

Posted
Posted

You will need to bake the crank in the oven for 45 minutes on 180deg to make sure the araldite cures properly, that way you can reliably rev it to 13000rpm. Also use rb20 pistons so you have plenty of piston/bore clearance. Might rattle a bit but it wont sieze. Be sure to run an 85w/140 oil, the thin stuff can sometimes cause the araldite to lose its grip, cant rely totally on the electrical tape to hold it together.......

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
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • drifter17a
      Rb25 trigger kit and timing misalignment

      By drifter17a · Posted

      Hey all,   I’ve got an RB25 with a trigger kit that includes a crank wheel, and I’ve hit a wall trying to sort a timing belt tracking issue. The belt either rides right on the edge of the cam/crank pulleys or walks slightly forward once the engine starts. It tracks okay-ish for a moment, then creeps right to the edge—and honestly, it’s stressing me out.   I’ve spent hours removing and reinstalling the belt, double-checking everything:   Tensioner setup is good, checked multiple times Idler pulley and washers are all in the correct places Followed the RB25 timing procedure step-by-step     The only thing I changed was the rear crank washer—I swapped the OEM one for a Neato version, and it made things worse. The belt now sits even more forward than before. I’m beginning to think the crank trigger wheel itself (from the trigger kit) is the issue—poor design or slightly off dimensions.   What’s strange is that with the previous belt setup, it actually ran fine for a couple of years—around 4,000 to 5,000 miles, even with hard driving and high RPMs. But even then, the belt was always riding right on the edge, and I know that’s not ideal or safe long term.   At this point, I’m debating whether to:   Machine a few mm off the crank trigger wheel to bring it back in line, or Replace it entirely with a better-designed unit     Only thing is, I already have the Cherry Hall sensors, bracket, etc.—I just want to replace the wheel only, not the entire kit. Anyone know a brand or supplier that sells just the crank trigger wheel on its own?   Would really appreciate any feedback—especially from anyone who’s run into this exact issue and found a reliable fix.   Thanks in advance.
    • Kapr
      Question about BoV on RB25DET NEO

      By Kapr · Posted

      Hi...a little refresh. Is Nistune gonna be enough to run BoV? Or do i need some proper ECU? 
    • Ozdavroz
      ATCC Amaroo Park 1987

      By Ozdavroz · Posted

      Yep that's pretty much what I want to see. Racecars that look and sound like the Group A but with newer tech underneath to make them faster and safer. I'm sure there's enough VK-to-VN commodore, E30 BMWs and Foxbody mustangs shells around to make up a decent number of cars with hopefully a couple of sierras, rx7 and R31s in there too. 
    • robbo_rb180
      WTB RB25 Gearbox NSW / central west

      By robbo_rb180 · Posted

      Contact Jessestreeter.com/Skevas Racing/JustJap for a new r34 rb gearbox or go a cd00# conversion. No point playing with unknown condition gearboxes.
    • robbo_rb180
      ATCC Amaroo Park 1987

      By robbo_rb180 · Posted

      Such a shame places like Amaroo Park have been redeveloped, smaller tracks always make for good racing. Cheers for sharing @PranK there's some good Lakeside video's too. Its so hard with older the cars as parts are so rare and everything was made for a particular chassis at that point in time. Even the V8 Supercar Blueprint era cars are all different between each chassis within a team as they learnt things and made improvements. The COTF cars between each Chassis builder is different too especially motor/oil systems/intakes. The Group A stuff is worth so much too especially chassis with good history. The only way to do it would be composite panels and similar engine drivelines to the original cars. Ford sierra running Focus RS driveline, Commodore running a short stroke LS/LT or a Falcon with coyote and a H Pattern dog box. Could use a standard ecu across all models with a Torque Map and DBW for parity which is not even used in Supercars currently. Hell a TCM is almost a full chassis car these days and the suspension is not even close to standard style in the front running cars.  
×
×
  • Create New...