Piston slap

[Airgne]

ok so i got pistin slap(had it since i bought the car, only when cold), but i noticed the gold flake in the oil the other day. was lloking around and i read something roger put up. just want to make sure about this. Phase I ej25 block + Pase II ej25 heads = no slap? if so why is this? been looking at this site http://www.importperformanceparts.net/i ... ubaru.html (http://www.importperformanceparts.net/imports/pek-subaru.html) dont knwo much about them, but they sound like they know what they are doing. im thinking i need around 3k to rebuild the the motor. i want a motor that will last and have a little more out of it. thinking TWE cams and spring kit. if i do this i need to know what bore and ratio i should look at. any help would be good. oh yeah i have read perdue and rogers sticky.

[Huffer]

Piston slap is typically attributed on the DOHC engine to the fact that the pistons do not expand enough to fill the cylinder cavity.

On your SOHC it is more of an issue - I think it has more to do with the actual rotating assembly rather than the actual piston itself. I never experienced the issue on my SOHC EJ20 in NZ, but that's obviously a different kettle when you have a SOHC EJ25.

[decke48]

like roger said DOHC piston dont expand. and to prevent piston slap the have long skirts on them but when the rings wear enough they allow a little compression excape enought to put the piston agains the wall causing the slap. if you getting piston slap in a SOHC you usally have a problem with out of round cylinder walls or pistons..

[Airgne]

i really not sure if it is piston slap. the heads were off at the dealership in dec08 so i hope they would have seen if there was a problem. as for the other things, what do you guys think?

[Airgne]

what could i do with a ej22t block? i dont want to turbo the car(might supercharge in futre).

[Huffer]

i really not sure if it is piston slap. the heads were off at the dealership in dec08 so i hope they would have seen if there was a problem. as for the other things, what do you guys think?

The dealer isn't going to measure the cylinders and the pistons - unless there's some very obvious movement going on (like major scratching of the cylinder wall) then they're going to assume everything is ok.

You could Frankenbuild the EJ22"T" by adding the SOHC heads with some nice cams - a few of the RS25 guys have done this with success. You could get away with a simple EM solution with the PP6 too.

[Airgne]

if i dont want it turbod what piston bore and ratio would you reccommend?

[Huffer]

No idea on the the bore, but for a fun NA machine I'd be aiming at an 11:1 comp ratio to run it on 89 gas safely.
That's about what I was going to see if I did the "SOHC" block + DOHC heads hybrid on my old GT. I had the block, and the heads, but never got around to buying the gaskets and installing it.

From what I understand from the RS guys, that combo can be run safely on the stock ECU.

[decke48]

stock bore is 99.5mm,

[Airgne]

anyone play with a cal like this? http://rds.yahoo.com/_ylt=A0geuratcyVK7 ... ulator.xls (http://rds.yahoo.com/_ylt=A0geuratcyVK7E8BXUlXNyoA;_ylu=X3oDMTEzMHBubnVoBHNlYwNzcgRwb3MDMgRjb2xvA2FjMgR2dGlkA0RGRDVfMTE2/SIG=12t5hqff1/EXP=1244054829/**http%3a//www.submariner.org/thepno95/TWE%2520compression%2520calculator.xls)

[Airgne]

if i did the phase I block and phase II heads what headgasket thickness should i get? i know the rod length changed in 99 with the phase II. do the pistons prtrude out like the ej22t does? if so anyone know how much?

[decke48]

phase I pistion putrude about .002 inch over the deck.. phase I block with Phase II heads and gaskets will have a Compression ratio of 10.13

[Airgne]

phase I pistion putrude about .002 inch over the deck.. phase I block with Phase II heads and gaskets will have a Compression ratio of 10.13

so a .24 headgas would be to small you think?

[decke48]

the only thing you have to be worried about is valve clearance. no real gains raise the compression to 10.22, you have to remember phase II heads have bigger CC combustion chamber, so not so ideal for high compression

[Airgne]

did a calculator last night and it came out to 10.3:1

101mm bore
79mm stroke
50cc camber
-.18 dome
.24 headgasket

[decke48]

my calc with phase I block and pistons and phase II heads
https://sl-i.net/FORUM/images/imported/2009/06/untitled8-1.jpg

[Airgne]

wish i could see it at work.