Hi all, Im currently in the process of making my RB30/25. . Ive got my bottom end but just considering weather or not I should rebuild it. . Ive read a lot of mixed stories about the rb30 crank having torsional vibrational issues about 7000rpm however I am not too sure? So the options are. . Pull the motor down, buy new pistons/rings, bearings, welsh plugs then that leads on to getting the block acid bathed. . Then balancing the bottom end (which should allow me to rev it safely without torsional vibration??). . Or. . . leave the bottom end as it is and hope it survives 7500RPM. . ? One other thing, exactly how much better will the motor go if the bottom end is "fresh/new"? And. . How much am I looking at for say: .040 oversized pistons, rings, bearings, pins, welsh plugs, bore, hone, balancing. . I am not sure on what brands to use. . Ill do the work myself apart from the obvious bore, hone and balancing. Thanks, Josh

Hey mate, if your bottom end is in good condition strap a head on it on and see how long it lasts, if you build the engine yourself unless you have the experience required you might run in to trouble with something letting go.. You will find a twin cammer wont need to rev out as high as 7000rpm to make good power and torque with the right turbo and fuel system, at least if you do the work to put the twin cam head on you can build up all the accessories for your current head & then when it lets go you will have a nice forged motor built ready to go in.

you will just need a decent harmonc balancer

any recommendations or places to go to get one?

yes any sugestions

hmmm leave it for now unless your cashed up set it up get it running then see how long it lasts then worry about building the engine when it spits that way the headache of the head conversion + wiring is out of the way + theres a good chance itll last a while, as for rb bottom ends there pretty spot on from factory for balancing, as for a new enigne well it will run alot smoother make more power make less noise use less fuel and last alot longer then the stock one u have. when you decide to build it throw some forgies and arp rod bolts in it atleast or even a set of h beam rods with everything you listed above and youll have a tough time trying to break it i build em all day long and you should have change from 3300 for all above and say 4000 with h beams also most ppl dont know this but the single cam heads have all valve springs facing one way except on 3 valves wich face the other direction its ment to help with engine harmonics so by changing the head this could be why they rekon it throws everything out, but yeh just get the conversion out of the way get it running then take it from there or if your cashed up do it all at once...

I would pull it down and freshen it up. When i done mine i reused the standard N/A pistons but had the crowns ceramic coated, new hastings rings and king bearings. I had an engine shop hone and acid dip the block along with the welding/maching of the R33 head water gallery. They also made a point of removing the plugs in the crank oil galleries and cleaning them thoroughly with a fine brush. I done all the assembly. Set me back about $1100 about 4 years ago.

righto thanks for the input guys. . for now I think i might leave the bottom end dead stock, rev it to 7500 and see how it handles it and how long it lasts. . if it feels not so good, ill pull it down and build it up then go from there. . Some original photos have not been recovered yet.

do it once and do it right! no use doing it twice!

Quote: Originally Posted by CRZPST do it once and do it right! no use doing it twice! Too right mate, ive been there n done that, just strip it down and put a set of forged rods n pistons in it..it's not like it's a hard job!

Depends on what other mods your running. Over 7000rpm you need a plenum and some decent cams. Mine with the stock cams made its peak at 6000rpm and held on nicely to 7000rpm. With 265 cams at 0 position (110 and 115 lca) it also makes its peak at 6000rpm but drops bugger all power until 7000rpm where it starts to nose over. However... Stick with stock cams and simply throw a plenum at it and it will make power all the way to 7500rpm providing your running a GT35r .82 or larger. Some original photos have not been recovered yet.

seriously man do it once and do it properly youlll always be chasing more power and your bottom end wont handle it, do your bottom end properly and even just leave your cams until u get bord and by then youll have the dosh to do the rest