Motor choice, compression #s

[klh6686]

Hey guys, i know a little about compression checks, but im far from an expert and was wondering which one you would choose and why.

1- 170-170-170-170-170-170 S1 engine2- 160-162-155-160-160-160 S2 engine3- 161-155-155-170-160-160 S1 engine

These are RB25's

I like 1 because it is dead even, but i don't know if that is a little high and what would make it a little high, other than that i had intentions on purchasing the s2 motor (#2), but im a l ittle scared by #2 and #3 cylinder. what is your educated opinions?

I'm going tomr to pick it up tomr, i will let you guys know how everything went with this engine importer as i couldn't find any info regarding them on here. Thanks
Modified by klh6686 at 2:00 PM 5/22/2006

[bmadd2402]

It really depends. a compression test is not the most accurate means of testing the health of an engine. the two with the lower compression could just have carbon buildup in the head, or maybe a gasket problem, but you never know till you further investigate. my suggestion is get them leak-down tested, and open up the valve cover and oil pan if you can and visually examine the internal components. the standard compression for the rb25det is 173.5, max limit is 130.8, with no more than 14.2 pressure variant bewtween cylynders. Good luck!!!

[Darius]

All of the motors are within compression specs according to the FSM. The standard compression (for an RB25DET) is ~176 psi with the low limit pressure of 133 psi. The max variance between cylinders is ~15 psi. Personally I would take either of the first two with the first being the best, obviously.

When I compression tested mine after I replaced the head gasket, my pressures were around 157-162 psi.

[Darius]

DAMN! You barely beat me to it!

[bmadd2402]

score one for me.

[klh6686]

Well, we decided to go ahead and pick up motor #1 because of the compression and are pretty happy with our choice so far, we got it home and began tearing it down for new goodies (waterpump, oil pump, etc. nothing crazy yet) and to our suprise we found a upgraded nismo clutch and flywheel. The only problem is its pretty much gone and we need to source a new disk as i'd hate to not be able to use this beefy pressure plate. anyways here are some pics of the clutch i speak of. i am not sure if any rb25 clutch disk will do as this one has a grooved extension on the back of the disk that matches with a grooved portion on the pressure plate. i have it marked in red on the last two pictures. if anyone can help me w/ this disk or if anyone knows if a normal disk is ok, let me know. thanks



This is what im talking about the grooved section, its marked in red.



Do you think a standard rb25 clutch disk can be used? that would be GREAT. Unfortunately, i don't know too much about clutches.