Rb25Det Neo With Rb30 Block Build..need Info Please

[R32Abuser]

Hi guys I'm new to this forum,

Ok iv purchased an rb30 block, it's been deck,honed, blue printed, balanced ,

New stock rb30 rods, race bearings, acl dura light pistons ra9301y 1.00 rib 0.025

Iv got a rb25det neo head that I plan on using for the build, I'm wondering what head gasket

I should use? Any info would be great please.

I've looked (for the past 10 minutes lol) for the pistons you state above. I cannot find them.

http://www.acl.com.a...80?OpenDocument

Apparently, duralite are only for 202 motors. Sure you dont mean another style of piston from ACL?

The only information (cc details etc.) I can find on ACL pistons is their Race series available in 2 styles for the RB30ET:

One with a 4.5cc dish (http://www.aclperfor...rgedPistons.htm)

and the other with a 10cc dish (http://www.aclperfor...orgedPiston.htm)

Key this into my static comp spread sheet above and you get:

4.5cc dish pistons with a Neo head = 9.06 static CR

10cc dish pistons with a Neo head = 8.42 static CR

Of course, this is ASSUMING you have a ZERO DECK HEIGHT on your block and the head is standard item and has a 51cc combustion chamber.

Edited June 8, 2012 by R32Abuser

[R32Abuser]

Also I have found some conflicting details regarding piston compression heights for some RB30 pistons. Obviously this will affect how the piston sits in the bore and therefore the static CR. So depending on these values the above static CR estimates may or may not be accurate.

This drives home the point to measure everything up before/during the build.

[Nuttyguy300]

Thanks for that r32 abuser, Them numbers are what's on top of the piston, i typed that number in google and it came up with some one quoting these pistons as acl duralight, I do know that they are acl pistons tho, And that they Are for a rb30et , ok so the head is standard, will just be taking it to head works to get it checked and stuff like that befor I put it on,

And by zero deck hight do you mean the piston being

Flush with the top of the block, ? Because yep that's all been done, and I'm thinking my piston is the 4.5cc dish, now for what head gasket to be used? I'm looking at a steel head gasket but not sure of what thickness

[wolverine]

Why don't you get your head prepped and cc'ed and double check the deck height and piston dish and tell us what compression ratio you want.

Hopefully can get an answer that won't be a guess.

[R32Abuser]

Ok so your deck height is the distance between the top of the piston at TDC and the top of the cylinder as per "deck clearance" below:

Obviously if the piston sits above the cylinder, this will increase the static CR (all things being equal). Similarly, if the piston sits below the cylinder, this will decrease the static CR.

I used a cometic 1.28mm head gasket as recommended in the RB30 DOHC guide. You can also use a standard RBXX head gasket IIRC. Once again, the thickness of your head gasket is going to influence your final static CR so first measure up what your motor has been built to and try a few different thickness head gaskets in a static compression ratio calculator. See what value you get and go from there.

Edited June 8, 2012 by R32Abuser

[R32Abuser]

Why don't you get your head prepped and cc'ed and double check the deck height and piston dish and tell us what compression ratio you want.

Hopefully can get an answer that won't be a guess.

Agreed.

[Nuttyguy300]

ok cool, yep ill get the head in this week to be preped etc, heres some photos of my piston and piston at the top of block,

[wolverine]

Ultimately I reckon a stock head gasket will be fine but it is such a pain in the arse if you have assumed incorrectly.

I have a neo head sitting in the garage and I was considering getting a basic RIPS bottom end sent over (which will probably be very similar to your setup) which would comp up nicely with a neo head but I will still double check everything before closing it up.

[R32Abuser]

Bare in mind, 0.020" (aka 20 thousandth of an inch) is only 0.5mm. If those pistons are sitting 20 thou below deck height its enough to shift the static CR quite a bit. In my build its enough to shift the static CR from 9:1 down to 8.64:1.

Food for thought.

[urtwhistle]

This is what I used on my first Rb30 6MKRY9608 http://www.aclperformance.com.au/NissanRB30ETForgedPistons.htm

and these on the 2nd build. that and there like $800.00 from the US or like 1200 if you buy them in Aus. NIS264405i05 http://www.us.mahle.com/C1256F7900537A47/vwContentByKey/W26HSFB8505STULEN/$FILE/2010%20AP%20complete.pdf

[t_revz]

Is it just me or do they look like more than 4cc dish. Prob 10

[urtwhistle]

they probly use the same pic for the 7.8 as the 8.5's

[t_revz]

I meant pics the OP posted

[Nuttyguy300]

Ok I'm going to get the head cc'd this week. Once done I'll repost my results with cc result and deck height

[Nuttyguy300]

Hey guys. I found a part number for my pistons.

Acl rb30 pistons

6mkry9301-1.00

Can anyone help me figure out what cc the dish is. It's got me f*kd.

[GTSBoy]

Why don't you titrate it?

[Nuttyguy300]

Titrate?

[Nuttyguy300]

I email acl and they for all the info I need in this piston

Bowl volume 12.0cc

 

Comp Ht 31.10mm

 

Clearance & Position .025mm At 45.3mm from bottom of skirt

 

So now saying that my head has about 51cc chambers and block deck hight being 0.5mm what size head gasket will I need to get my compression good

[Jayden.K]

Can someone post a link to that PDF file. Also looking for information on changing to a neo head

[Ben C34]

serious? The is an rb30 section it is in there.