Stealth-Z Posted November 25, 2008 Author Share Posted November 25, 2008 Now, as I had mentioned earlier, the RB30 pistons are 1.280 compression height pistons, and RB26 pistons stick out of the block by 0.020 inches, or 0.5 mm. This is referred to as "positive deck" clearance. The VG30 pistons, being 1.260 compression height would give you a "zero deck" clearance. Are you sure about the RB26 pistons sticking out of the block? I thought they had a lower compression height. Something around 1.18. When I took this photo, the RB26 pistons had a lower compression height than the stock RB30e. Quote Link to comment Share on other sites More sharing options...
Z-Monster Posted November 26, 2008 Share Posted November 26, 2008 Are you sure about the RB26 pistons sticking out of the block? I thought they had a lower compression height. Something around 1.18. When I took this photo, the RB26 pistons had a lower compression height than the stock RB30e. Careless, Stealth-z is right about the rb26's piston dome being lower then the rb30's. However careless is right about the vg30 piston crown being flush with the block deck. the reason why i was worried about my compression ratio is due to the fact that the difference between the rb30 and the vg30 pistons dome high being very much different and taking into consideration i had to bore out my block to stuff the vg30 pistons to fit i wold have messed around with too many variances to get the desired compression ratio. i was happy to hear careless rough calculation of my compression ratio being 8.2-8.9:1 but stealth-z did bring up a good point. if the calculation done by careless is in the ball park then i wouldnt bother with anything else and have blind faith in that calculation and assemble that engine as is. I will have it running by friday next week of which time i will take a full day sto run the engine in by clocking 1000km's on it and tune. So if you guys give me the confidence to seal the engine now and put it back into my car.. i will give you guys my actual hp figures and graph to give you guys something to look forward to...hihiihh... u guys are the best. i really do get very excited in coming to see the ideas we are exchanging here.... keep it up.. i really appreciate all the help and advice you guys are giving. cheers, Kevin Quote Link to comment Share on other sites More sharing options...
Careless Posted November 26, 2008 Share Posted November 26, 2008 Are you sure about the RB26 pistons sticking out of the block? I thought they had a lower compression height. Something around 1.18. When I took this photo, the RB26 pistons had a lower compression height than the stock RB30e. LOL i've seen that photo everywhere, I didn't know you took it (watermark!!!). AFAIK, and if you take a look back at fentin_fury's build with his blue block and CP pistons, the RB26 pistons are also half a millimeter proud of the deck. From what I've been told by a friend of mine (when selecting pistons and mentioning the positive deck clearance), he said "well the '26 pistons come over the deck anyway, so It's nothing to be concerned about..." Is this correct? It could be that given the compression height of the RB26 piston and the stroke, it would seem as though the piston is shorter so side-wall scuffing does not occur at extreme rod angles, and does nothing to the deck clearance once assembled. In either case, it will end up still being proud of the deck. can someone correct me on this? I'm not sure if it's right... When you post your piston manufacturer as well as the head volume (please do not go by the piston manufacturers specs, as I've stated before... there are tons of conflicting readings) I will then redo the specs if they differ. Quote Link to comment Share on other sites More sharing options...
fast-datsun Posted December 25, 2008 Share Posted December 25, 2008 I do not understand, JE builds me custom pistons all the time for may different engines. I provide there engineering dept the correct info and get the correct piston in 3-6 weeks or less every time.... Quote Link to comment Share on other sites More sharing options...
Careless Posted December 25, 2008 Share Posted December 25, 2008 read the first couple of posts. there was a mishap with the specs of the first pistons, and wiseco sent a second set of pistons that were also not correct. by the time Stealth-Z had found someone to machine the motor, the pistons would have most likely been out of the return-policy range. thus, finding the correct specs and milling the pistons down is the solution he decided to go with in order to maintain accurate and close quench distance. Quote Link to comment Share on other sites More sharing options...
synthtk Posted December 29, 2008 Share Posted December 29, 2008 So... I may have missed this in the previous threads but does anyone have part numbers for the different pistons available for the RB30/26 swap? I am looking for about 9:1 CR and know that CP and Arias apparently make pistons for this based on the offerings that SPOOL has. Obviously Wiseco has an option but with questionable results and I have seen MAHLE pistons for the swap on eBay also... but the dish descriptions and CR results all seem to conflict... RIPSNZ what do you guys use? Heck can I buy them from you along with a collar & belt? I have had a RB30 block and a set of your rods (well they are supposed to be your rods) in my garage for sometime now and would love to see this project going again... Quote Link to comment Share on other sites More sharing options...
S15 200sx owner Posted December 30, 2008 Share Posted December 30, 2008 Forgive me for saying this, but Eric has been posting updates and progress and his trials and tribulations over finding correct pistons to work for about a year and a half... and I know he's waited that long because his block has been from machine shop to incompetent machine shop throughout this whole ordeal... I have bought a set exactly like his that will work well for me because of the result of manufacturer specification errors that prevented AKWIKZ from using them as well (cancellation of project/compression too high), and that was over a year ago... so I know how long he's been at this. It's kinda too late to even bother making a comment like that, considering he asked for help a while ago and got no response. He (as well as I) have even posted on Skylines Australia, and the feedback is poor in respect to sharing info to help someone out. I mean... pistons, unless designed in-house like Engine Dynamics Roller Wave pistons are not the "underlying secret" of any build in my eyes. I just think it hurts the community, especially RB goers who are trying to get expensive parts and info from overseas without error when someone who could have saved "over complication" could have also spoke up earlier or perhaps gave a car/model/year that an off the shelf piston could come from. That's how I see it. And that's why I choose to post parts numbers when someone asks for specific parts. I've been through that, and I know how much of a bitch it is when you get the wrong parts. Careless, your comments got my back up a little. I think you will find that Rob (RIPS) wasnt attempting to be a smart a*se, but merely stating the fact that the correct pistons for the job are avaliable straight off the shelf. Looking at RIPS's joining date on Hybridz (july '07) he probably wasnt even on this forum when the original piston questions were asked. If he was aware of it, i am sure he would have chimed in and helped out then. I have always found Rob very helpful with things like this. And to follow on from Stony's original comments - If Rob offers any advice on building a performance RB30, you can rely on it being correct. Rob would have to be 'right up there' in the list of the worlds most experienced at building reliable and powerful RB30's. Forums like this can really benefit from the input of experienced people like Rob and it would be a shame to lose them because of comments like the above. Please don't take offence Careless, just thought i should make the point that this is probably the first he knew of the drawn out piston issue. Quote Link to comment Share on other sites More sharing options...
Careless Posted December 30, 2008 Share Posted December 30, 2008 Careless, your comments got my back up a little. I think you will find that Rob (RIPS) wasnt attempting to be a smart a*se, but merely stating the fact that the correct pistons for the job are avaliable straight off the shelf. Looking at RIPS's joining date on Hybridz (july '07) he probably wasnt even on this forum when the original piston questions were asked. If he was aware of it, i am sure he would have chimed in and helped out then. I have always found Rob very helpful with things like this. And to follow on from Stony's original comments - If Rob offers any advice on building a performance RB30, you can rely on it being correct. Rob would have to be 'right up there' in the list of the worlds most experienced at building reliable and powerful RB30's. Forums like this can really benefit from the input of experienced people like Rob and it would be a shame to lose them because of comments like the above. Please don't take offence Careless, just thought i should make the point that this is probably the first he knew of the drawn out piston issue. I understand where you're coming from. I know people like RIPSNZ and whomever else builds these engines day in and out don't have time to troll the boards and bring up posts from the dead. I know that Stealth has been working on this for a long time now and has made a couple of posts here and in other forums that many of the members of these boards are a part of. Maybe my posts was just taken in the wrong context (internet, go figure! LOL). I don't mean to say that it's required for someone to post if they know the info or whatnot. But care should be taken in reading what someone went through first to get to the point they are now before jumping to simple solutions which... in actuality, are not that simple at all when you're building on a budget. As I've said in the previous post, I've been in other forums too and got no response for things as simple as small parts interchanges that IM SURE others have been through or could easily verify. I've also been on the phone and contact through email with Gates, Arias, Wiseco, Total Seal, and ARP for MANY MANY RB30 parts that are obscurities in their own right... None of their measurements or guaging of the volumes in RB30's and 26's were the same at all. It's very hard to trust the compression calculation of a manufacturer. That's why I'm kind of stressing the fact that it's not as easy as pulling a piston off the shelf and installing it. Perhaps when you've worked with a piston over and over again from one brand, they'd be no different. But cross branded pistons of the same "specs"... no way. It's just not reliable enough. Quote Link to comment Share on other sites More sharing options...
RIPSNZ Posted December 30, 2008 Share Posted December 30, 2008 I'm not quite sure how I got cought up in the above, but I assure you any information I give will be from experience and totally in good faith. I had no idea how old the thread was (and I don't even check tbh) it just seemed to me that such a simple item to get like a RB30 piston was being made out to be far more complicated than it need be. Synthtk, if you want some correct pistons and any other RB25/26/30 parts for that matter, e-mail me rips@inspire.net.nz and i'll be more than happy to help if I can. Rob Quote Link to comment Share on other sites More sharing options...
Stealth-Z Posted December 30, 2008 Author Share Posted December 30, 2008 I am just trying to get the correct information to build a RB30/26 motor. There is so much misinformation out there to make your head spin off. RIPS has been successfully building them for years. I have no doubt about it. In August 2007 I purchased a timing belt and tensioner / idler kit from him. It came with directions on where to relocate the the tensioner stud. I purchased it knowing it was a proven application. In all my searching, I have still not found the answer to what sort of specs people use with these motors. My local sources are all what many say are old school racers from the 60's and 70's. They believe in measuring tolerances and want to get the best quench possible to squeeze out every last bit of horsepower. They take into account piston rock and valve clearances. The machinist that cut my pistons does machine work for AeroJet, a company that does research and development of rocket motors and other aerospace projects. But these motors are not the same technology. The machinist that did the valve job questioned the differences between the valve lash of the intake and exhaust. On RB26's the exhaust side runs a closer tolerance than the intake. It is backwards to someone who builds domestic (GM, Ford, Mopar, ect.) heads. In hind sight I should have just purchased flat top pistons and be done with it. My question's still remains though. What sort of deck height should I be running them at? Below deck? Zero? or above? What is an acceptable piston to cylinder head measurement? Are these motors not susceptible to detonation the same way the old 60's and 70's stuff is with today's fuel? Quote Link to comment Share on other sites More sharing options...
T04GTR Posted January 15, 2010 Share Posted January 15, 2010 so,, vg30 turbo or na pistons are the ones to get a 9:1 comp? and yes i have to agree. there is very much a "black art" secret society down under about anything internal.. you should try and get cam and combustion chamber info!! easier to get blood from stone.. Quote Link to comment Share on other sites More sharing options...
T04GTR Posted February 3, 2010 Share Posted February 3, 2010 ok, does anyone do a rb30 piston, 32mm comp height, with a 10cc~ dome? without huge valve reliefs cut into them? Quote Link to comment Share on other sites More sharing options...
kiwi303 Posted February 3, 2010 Share Posted February 3, 2010 Try PMing or emailing RIPS, as a RB tuning shop, Rob will be up on the state of play with RB30's Quote Link to comment Share on other sites More sharing options...
RIPSNZ Posted February 3, 2010 Share Posted February 3, 2010 ok, does anyone do a rb30 piston, 32mm comp height, with a 10cc~ dome? without huge valve reliefs cut into them? I have seen them in 32.5mm comp height (normal for RB30) with a 1mm dome and no valve releifs, pretty sure I can arrange a set. Any partiular reason for wanting only 32mm comp height? E-mail me if you want any more info. Rob Quote Link to comment Share on other sites More sharing options...
Z-Monster Posted March 9, 2010 Share Posted March 9, 2010 Guys, I have had to resort to using VG30DETT pistons as my RB30 block came from aust. with a big bad scratch on the piston sleave. I do have 9.1 compression ration hence i cannot boost high... I am curretnly running a max of 1.4 bar boost and the turbo spools fairly quickly. The engine is very responsive and can rev to 8500rm without problems. I would'nt know how a lower compression rb30 would feel but i have been driving my stock pistoned rb25det for 4 years before building a rb30 and the difference is huge. engine revs better on my rb30!!! guys do it cheap and good.. bore the block and stuff vg30dett pistons in your rb30 and you will have no problems if you are not chasing alot of boost. during tuning i boosted a max of 1.6bar and i was getting 600whp on a dynojet dyno... that on pump gar 97ron and a to4s turbo. z-monster out!!!!!! Quote Link to comment Share on other sites More sharing options...
wax Posted April 16, 2010 Share Posted April 16, 2010 Guys, I have had to resort to using VG30DETT pistons as my RB30 block came from aust. with a big bad scratch on the piston sleave. I do have 9.1 compression ration hence i cannot boost high... I am curretnly running a max of 1.4 bar boost and the turbo spools fairly quickly. The engine is very responsive and can rev to 8500rm without problems. I would'nt know how a lower compression rb30 would feel but i have been driving my stock pistoned rb25det for 4 years before building a rb30 and the difference is huge. engine revs better on my rb30!!! guys do it cheap and good.. bore the block and stuff vg30dett pistons in your rb30 and you will have no problems if you are not chasing alot of boost. during tuning i boosted a max of 1.6bar and i was getting 600whp on a dynojet dyno... that on pump gar 97ron and a to4s turbo. z-monster out!!!!!! So you don not have to skim the block bore and put them in ?? Ok sounds like a plan i am building an rb30dett and really only looking to run 15psi boost So slightly higher compression is what i am after for off boost driving Quote Link to comment Share on other sites More sharing options...
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