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Old 08-10-2008, 06:48 PM   #1
mrtrex
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Default 100% new 07 STI short block and I want to toss in some forged pistons. (questions)

1. Can these be just pressed in without going to a machine shop? I will be using standared bore cosworth pistons.

2. Will I need a retune? I dont plan on changing my set up right away from what it is now. I would go with the oem compression ratio.

3. Do I need to change anything else while Im in there. The car will never see more than 400 whp at the most and 380tq on a dynopack.

The car is a 2007 sti running stage 2.
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Old 08-11-2008, 02:34 PM   #2
jaxscuby
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standard bore drop in pistons should still be mic'd to
fit properly into cylinder bores.

the fact that you said "pressed" indicated that you
have not spent much time researching piston swaps.

but trying to obtain 400 whp with your wrx drivetrain
will shorten the lifespan of the drivetrain.

you might need a larger tmic or fmic to get to your 400 whp.

water / meth will help.

850cc injectors at least...and usual supporting mods.

be prepared to spend some cash..
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Old 08-12-2008, 12:09 PM   #3
Element Tuning
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1) The piston to cylinder wall clearance always needs to be measured and adjusted as needed. The same applies to the ring-end gaps. Sometimes these measurements are way off and sometimes they are fine. Never assume it's correct.

2) If your previous engine or pistons were damaged then yes you need to be retuned as it's likely your first tune caused the engine failure. If you feel your motor was damaged from something other than tuning then make sure you find the cause before building a new motor.

3) You just need to make sure you have found the cause of the failure, you have replaced the failed part(s), and you have thoroughly cleaned all the oil passages, lines, and fittings.

When in doubt leave it to the pros.

Thanks,
Phil
www.elementtuning.com
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Old 08-13-2008, 08:45 PM   #4
mrtrex
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Thanks for the info. My car is fine I am just building a short block for down the road. I think im going to just get the Raw Performance/Axis stage 1 block.
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Old 08-20-2008, 11:10 PM   #5
Mechie3
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How do you adjust the piston to cylinder wall gap? I know how to grind down rings, but not sure on the other.
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Old 08-21-2008, 12:03 AM   #6
norexyet
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Quote:
Originally Posted by Mechie3 View Post
How do you adjust the piston to cylinder wall gap? I know how to grind down rings, but not sure on the other.
That has to be done by a machine shop.
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Old 08-21-2008, 12:33 AM   #7
eastcoastbumps
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Quote:
Originally Posted by Mechie3 View Post
How do you adjust the piston to cylinder wall gap? I know how to grind down rings, but not sure on the other.
A machine shop has to bore with a machine that is similar to a giant drill bit, or hone with a set of filing stones.

http://www.youtube.com/watch?v=MAfdq217CJI&NR=1
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Old 08-21-2008, 09:14 AM   #8
Mechie3
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So if the gap is already too big you need to buy new pistons?
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Old 08-21-2008, 12:00 PM   #9
eastcoastbumps
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Quote:
Originally Posted by Mechie3 View Post
So if the gap is already too big you need to buy new pistons?
joke
Snap-on makes a piston expander. Its very expensive though, so you're just better off buying new pistons.
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Old 08-21-2008, 12:12 PM   #10
novacivic
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Quote:
Originally Posted by eastcoastbumps View Post
joke
Snap-on makes a piston expander. Its very expensive though, so you're just better off buying new pistons.
they also sell a board stretcher too for when you cut a piece of wood a little too short.
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Old 08-21-2008, 06:13 PM   #11
Robzilla
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All your questions can be answered with a little more research, try it.
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