25GTV Posted January 20, 2009 Share Posted January 20, 2009 As topic suggests also can i use my 25 pistons for increased compression... Just need some info cheers guys Link to comment https://www.sau.com.au/forums/topic/253436-rb30-bottom-end-with-neo-rb25de-head/ Share on other sites More sharing options...
gabzr34 Posted January 20, 2009 Share Posted January 20, 2009 I am pretty sure nothing needs to be changed, you may need lower mounts as the rb30 bottom i think is 38mm bigger. I am also sure rb25 pistons will fit but may not be the best option you should go with, forged pistons will definently be the best option. Aftermarket ECU is a must have and with a dyno tune you should be set mate. Link to comment https://www.sau.com.au/forums/topic/253436-rb30-bottom-end-with-neo-rb25de-head/#findComment-4380258 Share on other sites More sharing options...
R34GTFOUR Posted January 20, 2009 Share Posted January 20, 2009 this is exactly what im going to be doing, but i will be smacking GT35R on the side of mine The neo head has slightly smaller combustion chambers than the normal rb25/26 head, its somewhere around the 60cc per pot compared to 64ish cc in the normal head. This makes quite a bit of difference to the CR. With the na rb30 pistons, a deck block, thin hg and the neo head, that would have to net around the 10:1 if not higher. I think the na rb25 pistons might be a tad too much but just grab one of the online CR calculators and start plugging in numbers and you'll see what you'll need. I havent really looked that much into the na side of things since will be going the turbo route, but with mine acl rb30et pistons, neo head, decked block and a 1mm hg will get around the 8.5-9.0 CR mark. Obviously with the na route you would want much more than that Link to comment https://www.sau.com.au/forums/topic/253436-rb30-bottom-end-with-neo-rb25de-head/#findComment-4380463 Share on other sites More sharing options...
dori34 Posted January 21, 2009 Share Posted January 21, 2009 ^ R34GTFOUR, im thinking of doing the exact same thing. i want to build a high compression turbo motor but if i cant get forged high compression rb25de pistons, im going to be doing 25/30 conversion instead. Link to comment https://www.sau.com.au/forums/topic/253436-rb30-bottom-end-with-neo-rb25de-head/#findComment-4382110 Share on other sites More sharing options...
R34GTFOUR Posted January 22, 2009 Share Posted January 22, 2009 if you are using the neo head and want a high compression turbo motor (RB30DET), grab the flat top CP pistons that spool sell in his kit for the normal rb25/30. Depending how you set up the motor, you'll get anywhere from 9.0 to 10:1 CR, i doubt you'll want more than that I want mine around the 8.8 mark, still responsive but will still like some boost Link to comment https://www.sau.com.au/forums/topic/253436-rb30-bottom-end-with-neo-rb25de-head/#findComment-4383852 Share on other sites More sharing options...
25GTV Posted January 22, 2009 Author Share Posted January 22, 2009 Im aiming to run everything as standard just with the 30 bottom end and 25 pistons switched. Then a safc will prob do for the extra fuel. Wat machining is required? and do i need a better oil pump than the vL one? Link to comment https://www.sau.com.au/forums/topic/253436-rb30-bottom-end-with-neo-rb25de-head/#findComment-4383891 Share on other sites More sharing options...
GTS4WD Posted January 22, 2009 Share Posted January 22, 2009 You will need water pump collar and to relocate a pulley. Google "RB30DET" and .pdf. there is an awsome file out there. Link to comment https://www.sau.com.au/forums/topic/253436-rb30-bottom-end-with-neo-rb25de-head/#findComment-4383935 Share on other sites More sharing options...
R34GTFOUR Posted January 22, 2009 Share Posted January 22, 2009 (edited) You will need water pump collar and to relocate a pulley.Google "RB30DET" and .pdf. there is an awsome file out there. i'm going to take a stab in the dark and assume you meant oil pump collar instead, but thats only if he uses a widenose gtr pump Edited January 22, 2009 by R34GTFOUR Link to comment https://www.sau.com.au/forums/topic/253436-rb30-bottom-end-with-neo-rb25de-head/#findComment-4384741 Share on other sites More sharing options...
GTS4WD Posted January 22, 2009 Share Posted January 22, 2009 Lol.. thats the one.. I cam back after work drinks yestureday and I just begin to type.. Link to comment https://www.sau.com.au/forums/topic/253436-rb30-bottom-end-with-neo-rb25de-head/#findComment-4384970 Share on other sites More sharing options...
25GTV Posted January 24, 2009 Author Share Posted January 24, 2009 wat if i just use the rb25 one? Link to comment https://www.sau.com.au/forums/topic/253436-rb30-bottom-end-with-neo-rb25de-head/#findComment-4387073 Share on other sites More sharing options...
R34GTFOUR Posted January 24, 2009 Share Posted January 24, 2009 if its going to be a daily the rb25 pump will do the trick, you wont need the crank collar sine the rb25 runs a narrow nose crank like the rb30 If you are going to spend abit of $$ on the conversion and track it abit, an upgraded oil pump is good insurance Link to comment https://www.sau.com.au/forums/topic/253436-rb30-bottom-end-with-neo-rb25de-head/#findComment-4387836 Share on other sites More sharing options...
25GTV Posted January 27, 2009 Author Share Posted January 27, 2009 In terms of keeping the vvt wat must be done? Link to comment https://www.sau.com.au/forums/topic/253436-rb30-bottom-end-with-neo-rb25de-head/#findComment-4391536 Share on other sites More sharing options...
GTS4WD Posted January 27, 2009 Share Posted January 27, 2009 You will have to tap in to the oil galley and run an oil feed to it. The most common used feed is T’ing into the oil pressure sender feed. Link to comment https://www.sau.com.au/forums/topic/253436-rb30-bottom-end-with-neo-rb25de-head/#findComment-4392738 Share on other sites More sharing options...
25GTV Posted January 28, 2009 Author Share Posted January 28, 2009 Oh ok so its that simple. I thought i needed to have oil passages welded up in the head... Will the head bolt on with welding mods if i decide to ditch the vvt? Link to comment https://www.sau.com.au/forums/topic/253436-rb30-bottom-end-with-neo-rb25de-head/#findComment-4393667 Share on other sites More sharing options...
A31Shon Posted January 15, 2013 Share Posted January 15, 2013 iv got a neo 25de head and im building a 30det and just woundering if i should use the neo 25det oil pump instead of the standard one? or if a 25det non neo oil pump would be fine? Link to comment https://www.sau.com.au/forums/topic/253436-rb30-bottom-end-with-neo-rb25de-head/#findComment-6708029 Share on other sites More sharing options...
Gerg_R31 Posted January 22, 2013 Share Posted January 22, 2013 before this goes any further, and before a motor blows up a neo head has a smaller chamber, ive measured them between 52 & 55ccs in the tech section there is a simple maths formular i wrote up to work out your actual compression ratio, guessing = problem waiting to happen flat tops with neo head estimated around 9:1 static Link to comment https://www.sau.com.au/forums/topic/253436-rb30-bottom-end-with-neo-rb25de-head/#findComment-6718062 Share on other sites More sharing options...
luke gtr Posted February 4, 2013 Share Posted February 4, 2013 now youve all read that, blow up some motors and film results. Link to comment https://www.sau.com.au/forums/topic/253436-rb30-bottom-end-with-neo-rb25de-head/#findComment-6736080 Share on other sites More sharing options...
docaam Posted March 24, 2013 Share Posted March 24, 2013 before this goes any further, and before a motor blows up a neo head has a smaller chamber, ive measured them between 52 & 55ccs in the tech section there is a simple maths formular i wrote up to work out your actual compression ratio, guessing = problem waiting to happen flat tops with neo head estimated around 9:1 static So as OP posted what kind of compression it will reach Neo head and 30 block, couldn't find the answer and really bad in calculating compression I am looking around 11 for my NA setup Link to comment https://www.sau.com.au/forums/topic/253436-rb30-bottom-end-with-neo-rb25de-head/#findComment-6793489 Share on other sites More sharing options...
Recommended Posts
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 accountSign in
Already have an account? Sign in here.
Sign In Now