rb30 crank

[intrexin]

i know you can stroke a rb20 with a rb25 or rb26 crank but what whould be the end result if you used a rb30 crank? how much displacement would you gain whatabout power increases? i have a 20 right now but i'm wanting to make a nice back up plan if my motor ever blows, if i have to rebuild it i want to build it really nicly and turn it into something unique(r)

[themadscientist]

I beleive the formula was RB26 crank, with 4AGZE pistns for a 2.2. If you have an RB26 crank though, chances are you have an RB26 so why d!ck with a 20. Just a thought, from an RB20 owner.

[intrexin]

i think it was 26 crank and rod's or pisons i can't remember for a 2.4. And you could use a rb25 crank for either 2.2 or 2.3. i was wondering what you would get out of a rb30 crank, just as something that if i could find what could i do with it. And whats this about 4agze pistons i havn't heard that

[mnkypsycho]

rb30 cranks stroke is too long

[s13rb25]

mnkypsycho is correct. The RB30 stoke would be too long with any stock rods. It would put the pistons about an inch into the head. To use that crank youd have to get custom rods/pistons. For that money, you might as well have gone 25 or 26, since youd probably end up with about the same displacement. If you really want to be unique(r) get an RB30 short block and an RB25DE head and make an RB30DET with your current exhaust manifold/turbo setup. Since i doubt using the rb30 crank sounds fiscally responsible just build the 20 really well, or get a larger displacement motor if thats what youre after.

[Stealth-Z]

Most of the RB30's displacement is due to the extra deck Height on the block and the longer connecting rods.

I do not have exact specs on RB30 cranks. But I do know RB30's are not high rev friendly. The RB30DETT I am building will not need to rev high to make good HP and torque.

Go with the RB25 or RB26 crank and rod combos.

[intrexin]

cool thanks i would really like to do a rb30 but i reall doubt i'll ever get around to doing it i just want to have a full plan incase my motor ever goes

Stealth-z what kind of a car are you putting it in?if it's a s13/s14 are you worried about you hood closing and what kind of power are you shooting for?

[themadscientist]

the cool thing about the RB30 is the long rods. I read in a book by Smokey Yunick that long rod motors tend to build compression at high RPM making it a perfect NA motor for sustained full throttle. I would love to do a GTS-4 with a high compression RB30 and sports injection bodies. It would basically be a modern L stroker.

:::::::::::::::Update, mad needs coffee::::::::::::::::::I almost had it, it's been a while. It's that the piston dwells at on or near TDC longer with longer rods allowing power to be applied to the crank longer increasing torque. That's what I was trying to remember. Short rod motors accelerate from TDC faster so the torque drops off. Imagine pushing on someone who is walking in front of you and pushing someone who is running away from you, who can you push harder and longer? This also gives the valves more time to fill and exhuast the cylinder, more air needs more fuel and you get more power and less contamination from lingering byproducts of the last explosion.It also reduces the rod angle from crank to piston pin (the rod is at less of a cocked angle) this reduces piston side-loading and cylinder wear. This more linear angle to the crank also allows the rod to transfer energy more efficiently.

No wonder I wanted that engine!

[Stealth-Z]

interexin,The RB30 will be going into a 1978 Fairlady-Z (basically a right hand drive 280Z). As for power, I have not set any real goals as of yet. the motor is just an accumulation of parts right now.

[intrexin]

thats ganna be sweet make sure you post up pics. i love the old z's

[ISL33P]

rb30's dont mind revving at all. mine used to go to 8250rpm without any hassles. they do like a good oil and good oil flow.

admittedly it stopped making power at about 6000rpm but without the rev limiter one night and missed 2nd to 3rd gear, my computer recalled 8250rpm as peak revs. this was not a one off and used to see 7500rpm on a regular basis some reason it just liked to rev. it was mainly during burnouts and while trying to keep up with it in 1st and 2nd gears while trying to keep traction.

it made 400rwhp on 19psi and i am now building another one.

[Nismo Night Kid]

In a RB30DET or DETT Hybrid, that is the bottom end of a RB30 & head of a RB25DET or RB26DETT, how will this affect rpm, will it be the same 8000rpm? more or less? And will the crank handle the power that its just got in stock trim? much less modified? Really wanna know plz. Thanks.

[driftjunke]

Our 30 should be ready here soon, just waiting on parts from the other side of the world. We're using the 26 upper end, and the 30 bottom end.

E

[ISL33P]

stock crank can handle well in excess of 500rwhp and i have seen over 400rwhp on cranks with more than 250,000kms. they are tough as nails, trust me. my old car is still going and and has over 220,000kms with completely stock standard internals.

[rbsileighty]

What's the rod length on a 30? Actually if anyone has the rod length for the 20,25, and 26 I'd be interested to know that as well.

[REDLN]

how well does the hood close? What mounts are you useing? I have one coming soon. Here is a pic of mine when it was in it's beginning stage of the project.