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01-03-2011, 05:55 PM | #1 |
Scooby Newbie
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what is a good head gasket
i want to get a pair of some cosworth head gaskets and i just called to Subaru dealership and the don't even know the millimeter size or bore of any of the head gaskets they carry, and so my question is what millimeter and bore size head gaskets should i get that dose not change the compression ratio
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01-03-2011, 11:58 PM | #2 |
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What motor you running?
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01-04-2011, 01:23 AM | #3 |
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Realistically, the stock head gaskets are quite good if you properly prepare the block and heads. You need to be doing something crazy before alternative gaskets pay off. If you're doing it on a basically stock motor "just to be safe", you're barking up the wrong tree.
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01-04-2011, 11:18 AM | #4 | |
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01-06-2011, 12:11 AM | #5 |
Scooby Newbie
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im trying to get the HG for the 1998 dohc 2.5L that is still all stock the reason because i know these motors have HG problems so i thought of upgrading it and i would never have to worry about them again
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01-06-2011, 12:14 AM | #6 |
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The problem really isn't the HG itself, it's the design of the entire system.
The best you can do is to make sure the block and heads are flat to within a few tenths and obsessively clean all of the sealing surface. Then follow the factory torquing procedure properly. You'll have to have the engine out to do all of that. That's the best bet you have of putting off the problems as far into the future as possible. |
01-06-2011, 02:44 AM | #7 |
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so i should just get the factory HG even though those are the ones that fail more often i was thinking cosworth because they make those HG to handle alot more pressure
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01-06-2011, 02:58 AM | #8 | |
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For the NAs, I'll bet you dollars to donuts that the reason there's slightly less failures with Cometic gaskets isn't the gaskets. It's because they're getting used by guys who are being a hell of a lot more careful with their prep work. Look, if you take your heads off, peel off the old HG, slap the Cometic on there, and bolt the heads back on, the Cometic IS going to fail. But the guys who are trying to make big power, trying to do it right, and just happen to also be using Cometic gaskets don't just slap things together. They verify the heads and the block are flat to within a couple of ten thousandths of an inch. If it's not, they have a machine shop correct anything that's wrong. They verify that the surface finish (for the Cometics) is between 4 and 40 Ra on all the sealing surfaces. If not, they have a machine shop correct it. The obsessively clean the hell out of everything. They follow the recommended install procedure to the letter using torque wrenches that have been recently calibrated and angle gauges for the yield portion. If you do just the basics of that: Get a professional to check them for flat (and correct if needed), clean obsessively, and follow the factory procedure to the letter using the correct tools, the factory HG will seal reliably for long periods of time. |
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01-06-2011, 03:28 AM | #9 |
Former Vendor
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You're fine with using the stock one from the dealership. It is now a MLS gasket like what comes in the wrx/sti and not the crappy one that originally came in the car. 11044AA610 I believe.
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01-06-2011, 04:01 AM | #10 |
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thanks
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01-06-2011, 07:59 PM | #11 |
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What's the price one can expect to pay for the pair of headgaskets? Should the valve cover gaskets be changed out at the same time?
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01-06-2011, 08:06 PM | #12 |
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Cometic head gaskets are garbage.
if you're gonna go for a MLS gasket, get a Cosworth one. |
01-09-2011, 01:31 AM | #13 |
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Im doing my engine rebuild soon and have included cosworth sti 2.5l head gaskets with a 1.5mm thickness.
The OEM Subaru factory head gaskets should do you just fine because Subaru has updated the parts to a thicker design. But I decided to go baller with the cosworth head gaskets anyways. If you do decide to get them, make sure you go for the 1.5mm thickness. Stock subaru head gaskets are .054" thickness so the 1.5mm head gaskets are .059" thickness, that should help compensate for the loss of metal that has been shaved off by a machine shop. Going any thinner than that will increase your compression rate because the thickness is meant for turbo'd engines. Also the myth about cometic gaskets being ****, well......... everything is **** if you use them incorrectly. As previously stated above, do it right, have your heads measured and shaved for proper and maximum head gasket seal effectiveness. Best of luck =) |
01-09-2011, 03:02 AM | #14 |
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used both cosworth and cometic and havent had an issue with either, if your changing head gaskets it has nothing to do with valve cover gaskets unless you take the valve cover off, if thats the case it goes for any gasket if you seperate the parts, change the gaskets why not stick with oem?
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01-09-2011, 03:03 AM | #15 |
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Most of the EJ engines require the valve covers to be removed to access the head bolts. Just a few of the very older engines had the head bolts outside the valve cover.
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01-09-2011, 07:42 PM | #16 |
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the only reason want after market HG is because i dont really like how subaru changed the coolant flow on the multilayer HG AND I KNOW cosworth is the s***
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01-09-2011, 08:27 PM | #17 | |
Former Vendor
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Quote:
I'm not saying there's anything wrong with the cosworth gaskets, but we've never had a problem just using stock ones, even on our time attack car. |
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01-09-2011, 08:38 PM | #18 |
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maby i could be wrong but check out this like he shows you the two different HG
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01-09-2011, 09:39 PM | #19 |
Former Vendor
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Vehicle:2006 Mod Class STI TIMEATTACK!! |
What he's not showing you is how they line up with the passages in the head. That little tiny section of block that's showing with the "older" gasket is not the important part. That gasket is only meant for the 08+ sti which has different coolant passages in the head, so if you use it on something else you'll actually be blocking off more of the coolant passages. I do agree that for a phase 2 motor you should not use the stock gasket.
So, to summarize for a phase 1 n/a 2.5, use 11044AA610 for a phase 2 n/a 2.5, use 11044AA642 which is the 04-06 sti EJ255 gasket Additionally, you can't use 11044AA642 or 11044AA770 (the one in the video) on a phase 1 2.5 because they are thinner and will cause your pistons to contact the head. Last edited by AQ Motorsports; 01-09-2011 at 09:49 PM. |
01-09-2011, 10:28 PM | #20 |
Scooby Newbie
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but if i were to get cosworth i should get 1.5mm with a 101 bore
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01-10-2011, 12:25 AM | #21 | |
Scooby Guru
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01-10-2011, 12:26 AM | #22 | |
Scooby Guru
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Quote:
Stop obsessing about the gasket and just do the work correctly. |
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01-10-2011, 02:38 AM | #23 |
Scooby Newbie
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i will get the factory gaskets thanks for putting it so clearly i am little slow at times
Last edited by ditto151; 01-10-2011 at 07:38 AM. |
01-13-2011, 11:01 AM | #24 |
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does anyone know the thickness of the oem head gaskets?
for 2005 NA, I'm guessing part number 11044AA633? I'm trying to calculate compression ration change for my engine build.. cheers, M |
01-13-2011, 02:54 PM | #25 |
Former Vendor
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Join Date: Apr 2004
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Vehicle:2006 Mod Class STI TIMEATTACK!! |
do not get that part number. It is a single layer coated gasket which will leak again. Use the STi gasket ending in 642 I mentioned above. They are the same thickness (I don't know the exact measurement off the top of my head).
Also here is an 08+ sti head: you can see why the new -770 gasket is needed. |
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