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Old 04-20-2012, 03:24 PM   #1
danger1138
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Default Cometic vs. stock sti gaskets

Just wanna chime in with you guys what gaskets i should be using. Im in middle of hybrid build using 04 wrx ej205 heads and 06 sti shortblock.. I will have the option of machining the combustion chambers on the heads to
51 cc which will still net me a higher than normal co
Pressio ratio or going 56cc in order to retain stock sti compression.i will be running stock internals as well. So i have a set of stock sti head gaskets & i also purchased a set of cometic .60/1.5 gaskets.. Which combo should i use..
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Old 04-20-2012, 04:12 PM   #2
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I would go with 56cc and run the OEM STI gaskets. You'll make less power with the higher CR, due to the limitations (knock, etc) of pump gas. However, if you plan on only running e85, then the higher CR would work in your favor.
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Old 04-20-2012, 04:16 PM   #3
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No not planning on going e85.. Only planning
On using vf39, bigger injectors and supporting mods.( pnp exhaust mani, tbe,)
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Old 04-21-2012, 11:39 AM   #4
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The machine shop is charging 250 to machine heads to 51cc & resurfacing for the set.. They charge 450 for the 56cc job & a resurface.. Would it be feasible, with my power goals, to just take the 51cc job, pair it with thicker cometic gaskets, then pro- tune.. Im on a budget thats why i ask.. Or like the old saying goes .." spend a little xtra $ and get her done right the first time"..
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Old 04-21-2012, 12:21 PM   #5
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Quote:
Originally Posted by danger1138 View Post
No not planning on going e85.. Only planning
On using vf39, bigger injectors and supporting mods.( pnp exhaust mani, tbe,)
Don't PnP the exhaust manifold. you'll kill the spool, run a El header.
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Old 04-21-2012, 12:37 PM   #6
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I wanna keep the sound though
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Old 04-21-2012, 12:43 PM   #7
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it's the sound of inefficiency



Run a un equal length header then, just don't port the OEM ex. mani. There are steps in the manifold for a reason.
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Old 04-21-2012, 01:07 PM   #8
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Well i didnt pot em myself, they are grimmspeed pnp also coated.
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Old 04-21-2012, 01:15 PM   #9
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I ran a 2.5 with 2.0 heads on pump gas on and off for years, you will not be limited. It is hardly higher compression. Stick with the stock sti gaskets. I speak from lots of experience, not just parroting what I have read.

DK
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Old 04-21-2012, 01:20 PM   #10
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Quote:
Originally Posted by ronzogonzo
it's the sound of inefficiency

Run a un equal length header then, just don't port the OEM ex. mani. There are steps in the manifold for a reason.
I wonder what the reason aftermarket headers don't have these steps if they are that important. I agree that having some of these steps are important but there is so much resistance inside oem manifolds and a GOOD pnp could take care of it.

Pnp headers are proven to work, cross pipes work and up pipes work... where did you come to the conclusion that it kills spool?
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Old 04-21-2012, 01:23 PM   #11
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Quote:
Originally Posted by danger1138
Well i didnt pot em myself, they are grimmspeed pnp also coated.
Here is my vf39 on 06 sti. Spike it to 25-26 psi around 3500-3600 rpm tapered it to 15-16 psi at redline. I have grimmspeed PnP headers, I recommend them if spool is what you are looking for as cast header will hold in more heat than tubular. If HP is what you seek them EL may be better option . My headers still have stock heatshields and them and uppipe are heat wrapped also.



If you can't see the pic since I'm on my phone here is link http://pbckt.com/pc.Ufhqeq
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Old 04-21-2012, 02:38 PM   #12
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Originally Posted by wrxsubiemod View Post
I wonder what the reason aftermarket headers don't have these steps if they are that important. I agree that having some of these steps are important but there is so much resistance inside oem manifolds and a GOOD pnp could take care of it.

Pnp headers are proven to work, cross pipes work and up pipes work... where did you come to the conclusion that it kills spool?
A GOOD quality/designed header will help aid with exhaust scavenging, and increase spool.

I thought before I read this it was a good idea too, but this makes sense.

From Dom @ MPS,

http://forums.nasioc.com/forums/show...2&postcount=15


-Phil
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Old 04-21-2012, 02:55 PM   #13
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Hey guys enough with the manifold comments some are pro pnp mani, and some are against it.. Blah,blah, blah. I wanna hear your opinions on what is a better combo, head work to gasket wise..?
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Old 04-21-2012, 03:20 PM   #14
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The best option is to have the combustion chambers worked over.. they don't necessarily have to be matched. Thicker head gasket is another option that works, but isn't ideal.
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Old 04-21-2012, 03:23 PM   #15
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you need to machine the heads for it to work correctly. OEM head gaskets are what I would use.


if you want to do it right.

http://forums.nasioc.com/forums/show....php?t=2343203
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Old 04-21-2012, 03:25 PM   #16
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Quote:
Originally Posted by ronzogonzo

A GOOD quality/designed header will help aid with exhaust scavenging, and increase spool.

I thought before I read this it was a good idea too, but this makes sense.

From Dom @ MPS,

http://forums.nasioc.com/forums/show...2&postcount=15

-Phil
Yup read that too and does make sense but basically just backed up everything I said lol.

As for head gasket I would run stock with some arp studs.

Have the heads opened up enough to get your compression ratio where you want it. A good port shop will cc the heads and take the gasket into account when working on the head

Last edited by wrxsubiemod; 04-21-2012 at 03:31 PM.
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Old 04-21-2012, 03:37 PM   #17
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Yea the shop gave me two options;
-51 cc which will net me a bit higher than normal cr using stock gaskets. $250
-56cc which will net stock sti Cr using stock gaskets. $450
But since i have two sets of gaskets, cometic being the thicker ones, was wondering if i could cut cost by going with the $250 head option in conjunction with the cometics. Your thoughts..
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Old 04-21-2012, 05:37 PM   #18
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Quote:
Originally Posted by ronzogonzo View Post
you need to machine the heads for it to work correctly. OEM head gaskets are what I would use.


if you want to do it right.

http://forums.nasioc.com/forums/show....php?t=2343203
This is FALSE. There is no need for it. 1000's of Hybrid setups WITHOUT matchined CC'd were built for 5+ years before this whole matching the CC's thing became popular. I've built many this way, no issues for pump gas tuning. My car made 430whp on pumpgas with a ~9.2:1 hybrid setup, and never had knock issues, and never blew up because of it. I'm getting tired of people saying it is required. It is not. Period. If it was, then we'd have experienced so many blown hybrids when they first started being built, that we would have looked for the solution. But that wasn't the case. I'm tired of people without experience without experience just spouting this information. Yes, theories are great and all (i am a physicist after all) but they do not matter when real world experience doesn't follow. There have just been WAAYYY to many hybrids built the original way, and are just fine, to claim this is a requirement and scare ppl into doing this. I had 29-30psi on my hybrid for about a year of pure asshattery and that motor is perfectly fine. Currently in my bros car running beautifully. Can people please just stop saying its required, when it definitely is not. There is absolutely NO DEFINITIVE PROOF that unmatched CC's cause mad detonation. There's only theories.

/end rant (this has been building in me for a while)

DK
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Old 04-21-2012, 05:38 PM   #19
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Oh and sti gaskets will be perfectly fine, thicker headgaskets is not the cure for "higher" compression.

GLWYB

DK
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Old 04-21-2012, 05:56 PM   #20
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Dam bro u almost blew a blood vessel.. Lol
Anyways i already shipped em out to the machine shop and will get em compression matched just to b on safe side.. I wanna reliable, cant emphasize this enough; RELIABLE BUILD. So off i go.. Thanks for sharing that though.
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Old 04-21-2012, 06:08 PM   #21
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Had to get my point across some how

DK
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Old 04-21-2012, 06:36 PM   #22
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I always thought it was funny that matching the chambers was suddenly "required" for a safe build, when people had been building reliable hybrids for years before that without problems.


I think it's a good thing to do and probably the best way to bring the compression down, but it certainly isn't required. It would be interesting to see some real comparisons of before and after.. I have a feeling the difference isn't as much as most people make it out to be.
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Old 04-21-2012, 06:45 PM   #23
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There was a comparison done.

The ported chamber made more safer power.
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Old 04-21-2012, 06:54 PM   #24
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Quote:
Originally Posted by wrxsubiemod View Post
There was a comparison done.

The ported chamber made more safer power.

link?



My heads are about to come off and I'm going to have them worked over a little.. I was thinking I could do a before and after, but I'd rather not have to pay for the extra tune.. especially if someone else has already done it.
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Old 04-21-2012, 07:50 PM   #25
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