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'00 RS w/ 05 STi swap
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Discussion Starter · #1 ·
round 2 of comparison - what are the pros and cons of each head gasket, what one do you feel is better, and what would you recommend for an ej251/ej257 build
 

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2002 2.5 RS-T
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2,960 Posts
round 2 of comparison - what are the pros and cons of each head gasket, what one do you feel is better, and what would you recommend for an ej251/ej257 build
the cometic is a bit thicker....so it will lower your compression slightly....

as for which on is better.....they both do their job well :)
 

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1998 Subaru Impreza RS - RBP
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1,605 Posts
As you know, I'm going with stock tri-layer STi gaskets and I trust them, especially since I have ARP headstuds now. :)
 

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'00 RS w/ 05 STi swap
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436 Posts
Discussion Starter · #4 ·
yes i will def be running arp head studs as well with this build - its the only way to do!! haha i had a feeling you would chime in nick!
 

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New to me 2006 Blue Impreza
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100 Posts
I read that the thicker head gaskets will change your cam timing 1 degree up on one side and 1 degre down on the other.
 

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overdeveloped beater
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8,335 Posts
I've used Cometic exclusively in the last 4 builds I've done. The only issue I encountered was using the OEM STi thickness gasket on a phase I bottom end. It was too thin and allowed the pistons to kiss the heads. They came out in exchange for proper thickness gaskets and all has been well.

The Cosworth gasket is virtually identical to the Cometic, so take that into consideration when choosing.
 

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2015 STI Crystal White Pearl
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1,861 Posts
The Cosworth gasket is virtually identical to the Cometic, so take that into consideration when choosing.
reeeeally, i WAS gonna get cosworth's but i figure my build wasn't as extensive so i went for the cometic's. thanks for making that clear.
 

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project blackbird.
'01 RS, '81 Fiat Spider
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Anything Cosworth is better than anything Cometic, as long as you're a brand whore like me.
 

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2001 RS Emerald Green Racekor
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Make sure you are installing and using the proper installation method for the arp's or they will fail.


"KIT # 260-4701 HAS 11MM STUDS IN IT. SO THE TORQUE WITH ARP MOLY LUBE
WILL BE 85 FT LBS. DO THIS IN 3 EQUAL STEPS, YOU WANT THE FINAL TO BE AT
LEAST 25 TO 30 FT LBS OF TORQUE. YOU DO NOT USE ANY TORQUE ANGLE WITH
OUR FASTENERS. IF YOU ADD AN EXTRA 90 DEG TORQUE TO THE STUD AFTER TORQUING IT TO 85 FT LBS YOU WILL MOST LIKELY FAIL THE FASTENER.

NOW THE STUDS WILL GO IN THE BLOCK HAND TIGHT ONLY NO MORE THAN 1 OR 2
FT LBS OF TORQUE. IF THEY GO INTO WATER YOU NEED TO USE A THREAD SEALER,
IF DRY HOLES THEN USE THE MOLY.
WITH A NEW STUD YOU NEED TO RUN IT THRU THE TORQUE CYCLE 3 TIMES TO
BREAK THE THREADS IN. WITH THE 4th TIME THE FINAL TORQUE.

THE KIT YOU HAVE IS A HIGHER GRADE MATERIAL THAN OUR REGULAR STUDS. REGULAR
STUD = 200,000 PSI KIT # 260-4701 = 220,000 PSI.
 

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MY99 GF4 EJ227 JDM 6spd
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5,273 Posts
round 2 of comparison - what are the pros and cons of each head gasket, what one do you feel is better, and what would you recommend for an ej251/ej257 build
For those engines, the STi HG works well no doubt. When you start pushing 500whp++ you begin to worry about the heads lifting. The STOCK HG seems to work very well. For my EJ22T build I use the '97-'98 EJ22E, which is a 3layer HG just like the STi HG. I have no problems with it, but I am only pushing about 300whp.
 

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2015 STI Crystal White Pearl
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1,861 Posts
I got a good question for you arp stud users: do you re-torque your studs every 1000 miles like some users do/claim?

I feel there's no need to, imo. I think by doing that, you're just weakening the head gasket. I mean c'mon, if arp studs are supposed to be 220,000psi strong, and proven to hold more pressure than oem, why would they need re-torquing after so many miles? we don't have to do it with oem bolts, yet with the arp's? I don't get it. thoughts?
 

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2001 RS Emerald Green Racekor
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1,454 Posts
As per ARP if you retorque after following the proper procedures you can cause the fastener to fail prematurely.
 
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