ok here is the run down i have an 04 wrx with an ej25 with cp pistons. it is also a hybrid motor with wrx heads, turbo, and fuel system. now my problem is now i have about 300 miles on the set up. it has not been above 3500 rpm and not given more than half throttle cause i heard i need some timeing taken out.

ok so below 1100 rpm it sounds like a knock in the block some where. i am well aware of normal valve sounds but it is louder than that. i have also talked to some of my domestic friends and they are talking about piston slap because of haveing the forged pistons.

so is this normal and nothing to worry about?


Let me know
Gil

 

running a 2.5L block on stock 2.0L ECU, you sir, are playing w/ fire.....I'm assuming you destroyed your stock block?

you need proper EM & a custom tune to run you're setup.

Jeremy

 

it did it when i first put the motor together. as for the ecu stuff i know and i am saving for an access port so i can change some timing.


Gil

 

Fixed thread title to something more descriptive.

I'd really avoid driving a 2.5 swap using WRX externals without tuning.

Did you buy the short block ready to install, or did you assemble the piston/rod assemblies into the block before you installed it?

Forged pistons can run a little noisier than cast or hyperuetectic pistons because they are typically installed with more piston-to-cylinder wall clearance to allow for expansion as they heat up. I've used forged pistons in non-Subaru engines before and didn't notice the difference in noise when cold or hot, but these engines were professionally assembled with proper clearances by honing the cylinder bores on a Sunnen CK-10.

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0==WW==0
"…axles of evil…" - george w. bush

 

what CP pistons are you using too? if your running of the shelf ratio for a 2.5 with WRX heads that you are definitly running WAY too high a CR unless you are running thicker head gaskets

 

ok the engine was assembled by world one performance. i then attached all parts and installed the motor into the car. the knocking will only be under 1100 rpm the motor sounds great other than that rpm range. even after warmed up.

also i would like to say i might be hyping this up too much but the knock is really loud. it is just "noticable" so i don't want people to think it sounds like a monkey with a wrench in my motor. (that is my tranny right now)

as for the cp pistons i am unsure, but i am useing a cometic head gasket with arp head studs.


Gil