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Old 07-01-2008, 03:53 PM   #1
lemon19mmm
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Default My Hybrid Questions.. Thanks

EJ257 shortblock
100 mm JE Pistons/8.5:1 CR
Cosworth bearings
WRX HEAD/ STI CAMS

My goal is a fun and reliable auto-x,HPDE car.

1.Should I run thicker HG to keep CR low? If so, what's your suggestion?

2.Do I need to do some mods to make the combustion chambers match the 100mm bore on STI block?

3.How hard is it to swap the sti cams? I alreay block the holes on the sti intake cams. I did cams swap in sr20det and evo before.

I was running a normal fmic 18G setup and ra gears before I spun a bearing in my EJ205.

Thanks in advance..
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Old 07-01-2008, 06:11 PM   #2
UP2MTNS
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have you built it yet? you can custom order your pistons to give you the CR you want with the stock HG thickness (most recommended).

lower CR is safer, especially if you're going to track it.
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Old 07-01-2008, 06:37 PM   #3
lemon19mmm
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The shorblock is done. Therefore, if I wanna make the CR lower, I think playing with HG would be my only option.


Thanks..
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Old 07-02-2008, 01:40 PM   #4
lemon19mmm
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bump for more replies...
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Old 07-02-2008, 02:34 PM   #5
kellygnsd
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You could massage the CC on the heads and use very dished valves to lower compression a bit. Have you heads c.c'd and calculate it out.
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Old 07-02-2008, 02:55 PM   #6
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Quote:
Originally Posted by UP2MTNS View Post
lower CR is safer, especially if you're going to track it.
Why is that?
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Old 07-02-2008, 03:47 PM   #7
rainwrx
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Lemon, I too have a higher compression hybrid. I've been advised by several engine builders and tuners to avoid using a HG to deal with compression. The correct way to do that is with pistons. I've also been advised that the higher compression is not really an issue -- just tune properly for it.

At the end of the day, what matters most are your goals for that engine and car. In my case, I wanted a strong daily driver that I could enjoy at several HPDE's a year. Not a dedicated track car or all-out HP monster by any means.

What are your goals?
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Old 07-02-2008, 07:10 PM   #8
lemon19mmm
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kellygnsd-- sounds like a good idea...Thanks

rainwrx-- it's not my daily driver and it's not a crazy race car either. Like I said, my goal is a fun and reliable HPDE, auto-x car.

Thanks guys..
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Old 07-03-2008, 09:01 PM   #9
lemon19mmm
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Any more suggestions?
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Old 07-07-2008, 04:03 PM   #10
lemon19mmm
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bump.....
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Old 07-07-2008, 04:36 PM   #11
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These are your options. If you want to change you CR you can do it with pistons, a HG, or changing the volume of the heads. The head gasket is the least desirable method to do so.
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Old 07-10-2008, 12:07 PM   #12
bluescoobywagon
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I'm opening the chambers in my 2.0L heads to the 2.5L bore. This will have several benefits. It lowers the compression. It unshrouds the valves. It removes the sharp edge from the bore.
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Old 08-28-2008, 03:24 PM   #13
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Quote:
Originally Posted by bluescoobywagon View Post
I'm opening the chambers in my 2.0L heads to the 2.5L bore. This will have several benefits. It lowers the compression. It unshrouds the valves. It removes the sharp edge from the bore.
Any drawbacks to this approach? I've had this recommended to me, though the machine shop costs were going to be close to the price of aftermarket pistons.
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Old 08-28-2008, 03:27 PM   #14
kellygnsd
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Quote:
Originally Posted by Snowphun View Post
Any drawbacks to this approach? I've had this recommended to me, though the machine shop costs were going to be close to the price of aftermarket pistons.
Price
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