Forged Pistons?

[al_r33]

Hey people,

Got my motor rebuilt about 9months and the Piston that were meant to be put in were Arias Forged Pistons 20tho! I have had problems with compression ratio's so the head has been pulled off and on top of the pistons there is this information

RA9603X 0.50

RIB 0.10R1

Can anyone shed any light on these as to what specs these pistons are? As we are trying to work out the Current compression ratio of the motor!

Any help would be appreciated!

Cheers

Alan

[r33_racer]

Well they are 20 thou over....the 0.50 is the oversize measurement. Havent you got a spec sheet with the pistons when you bought them? Or cant you get them from the suppliers website? That will have all the info you need about the piston inorder to work out your CR, more importantly you need your head cc and headgasket thickness. Head cc should be about 64cc i think.

[legend01]

Hi al_r33

I have 3 sets of arias forged pistons on the desk with me they are rb20det 78.5 rb20det 79mm and a set of rb25det 87mm pistons,none of them have any information on the top's of them they are all marked with a job no on the bottom of the piston and thats it no other marking's .I had to go to the aria's web site to find out what they were just had to search the job no in, so I'd be a bit dubious they were aria's unless someone else has a bit more info than I do

Cheers Peter

[al_r33]

Well does anyone know what brand they could be! & know i was not given a specs sheet when it was rebuilt!.

Edited September 15, 2006 by al_r33

[al_r33]

anyone?

[grandmasterb]

I would be asking where you bought the pistons from cobber for info as a starting point!!!

[R31Nismoid]

I would be asking where you bought the pistons from cobber for info as a starting point!!!

Agreed... thats where it begins and ends, regardless of whether you were given a spec sheet or not

[al_r33]

Yer but the guy that rebuilt the motor moved to qld & we cant track him down & the bought the pistons.

[T04GTR]

should be maby .1 higher

[al_r33]

What should be 0.1 higher?

[Cubes]

I've just had a look through the pics of forged pistons I have.

Arias, CP don't appear to have stampings on top, all on the bottom.

Wiseco have stampings on the top BUT are nothing like what you list.

[al_r33]

cheers!

[blind_elk]

Well does anyone know what brand they could be! & know i was not given a specs sheet when it was rebuilt!.

Looks like the same markings on a set of ACLs I have.

[al_r33]

can you be sure or just from what you remeber? Do you have the spec sheet for them if you have rb25 20tho ones?

Cheers

[blind_elk]

Mine are 40 thou, but were never installed. . No actual spec sheet. This is the meaning of the markings, as explained on the box:

RA9603X = Part Number

0.50 = Oversize (0.5 mm / 20 thou)

RIB = measure bore clearance at RIB (= Bottom / skirt) of piston

0.10 = Piston to bore clearance (mm)

R1 (RI ?) = Batch number

Contact ACL, and ask them the cc of the dome for your C/R calculation.

[al_r33]

Thanks mate! That has just made it easyer!

[blind_elk]

Specs at:

http://www.aclperformance.com.au

According to the specs, these pistons are a 8.5 C/R

[al_r33]

ACL told me that they are Ross Forged Pistons which he said should be 8.5 to 1. Does anyone know what the std Headgasket size is on a r33 gtst? 1mm or 1.2mm