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Hey guys,

What does everyone think in regards to going with a hybrid motor aka rb25/30, or going with a stroker and rb26 head?

The main build plan is just for a dirty old r31 with a big dash of sleep =D then take it to dyno days and snap ridiculous boost into it, see how well it takes it

Myself building it, with a good mate who's a qualified mechanic (and knows RB's pretty well)

Opinions? I'm not overly a fan of the rb25/30, the plan was a stroker with rb26 head as the 26's love revving more, but i'm interested to see what people have to say?

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oh the budget is around the 20k area,no labour costs involved ;) just tuning, the only thing i'm wary of is with bigger turbos you need higher rpm, and RB30 cranks aren't known for their perfect harmonics at higher revs so where the 26 would be laughing and saying MOAR BOOST the RB30 would be a bit dodgy and losing stability.

I know the fact of the RB30 stability issue from an example given in one of my engineering lectures in engineering design, it came up as the lecturer loves skylines haha, wasn't perfectly balanced from factory

oh the budget is around the 20k area,no labour costs involved ;) just tuning, the only thing i'm wary of is with bigger turbos you need higher rpm, and RB30 cranks aren't known for their perfect harmonics at higher revs so where the 26 would be laughing and saying MOAR BOOST the RB30 would be a bit dodgy and losing stability.

I know the fact of the RB30 stability issue from an example given in one of my engineering lectures in engineering design, it came up as the lecturer loves skylines haha, wasn't perfectly balanced from factory

:ermm:

oh the budget is around the 20k area,no labour costs involved ;) just tuning, the only thing i'm wary of is with bigger turbos you need higher rpm, and RB30 cranks aren't known for their perfect harmonics at higher revs so where the 26 would be laughing and saying MOAR BOOST the RB30 would be a bit dodgy and losing stability.

I know the fact of the RB30 stability issue from an example given in one of my engineering lectures in engineering design, it came up as the lecturer loves skylines haha, wasn't perfectly balanced from factory

Ha ha ...you better inform R.i.p.s he doesnt know what he's doing and tell him he cant be revving those rb30 cranks past 9000rpm.laughing-smiley-014.gif

Many guys have built very strong rb30's ..but a dirty r31 deserves no more than 25 head slapped on a 30 bottom end.

I know the fact of the RB30 stability issue from an example given in one of my engineering lectures in engineering design, it came up as the lecturer loves skylines haha, wasn't perfectly balanced from factory

Dodgey lecturer, balance the bottom end properly and it should be fine. I wouldn't be revving a normal VL RB30E over 7000rpm - but if you are going to build a new engine those generalisations don't apply.

He could be right, I'm not saying anything either way but obviously there are alot of RB30's that rev ludicrously hard so in applications terms IE in our cars the difference may be so minimal that it isn't worth discussing.

There is however a 14% increase in stroke length between a 26 and a 30.

All RB's have bad harmonics from factory, it is nothing simply assosiated with the RB30 crank not being perfectly balanced. With the length of the RB crank, harmonic vibrations are always going to be an issue.

Ha ha ...you better inform R.i.p.s he doesnt know what he's doing and tell him he cant be revving those rb30 cranks past 9000rpm.laughing-smiley-014.gif

Many guys have built very strong rb30's ..but a dirty r31 deserves no more than 25 head slapped on a 30 bottom end.

+1

Well OP how about you just go for Win win win.

Get the Nitto 3.2 stroker kit with the counter balanced crank, Rev its arse off, make more power and torque than any jap stroker kit ever dreamed of And save yourself a wad of cash over the ridiculously priced japanese branded counterparts.

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