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Old 10-21-2010, 10:26 AM   #1
EmaciatedCow
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Default why are my head gaskets blowing?

little background on the motor: pte 6265, darton sleeved, weisco 100, manley i-beams, new black crank, 255 heads (ported) with bc280 non avcs cams, and p&l 13mm head studs

the block has been decked twice at 2 thou (so 4 thou off, the heads have also been decked the same amount)

from what the machine shop said, my pistons are 4 thou above deck and my compression ratio is through the roof. and thats why its blowing them out after only 15 minutes.

to remedy this, i got so retarded thick head gaskets ( like .14" or something crazy) and the motor didnt have the correct quench. but when i took the motor apart again, the head gasket was blown in the same spot. BUTTT 2 of my head studs pulled through on the piston too. so i dont know if we can count that one.

is this really what could be wrong? or is there something else i'm/their missing here?

im a little frustrated because of how long its been since the build started and all of these head gasket problems. any help is much appreciated

*** they all blow on the same piston too
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Last edited by EmaciatedCow; 10-21-2010 at 10:47 AM.
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Old 10-21-2010, 10:31 AM   #2
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either warped head or not a true flat mating surface BUT it Sounds like you need to go back to the drawing board and see exactly what compression you had as you answered your own question kind of as to why it's not going to be able to be tuned with some retarded high compression(which not as many tuners are use to on subaru apps)
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Old 10-21-2010, 10:37 AM   #3
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Stupid high CR wont blow a head gasket after just 15min. Many NA cars run well into 15:1, along with diesels and dont just blow head gaskets for no reasons.

As stated above: Warped Head, Not a true Surface, or your sleeve dropped.
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Old 10-21-2010, 10:39 AM   #4
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it was decked the second time to make sure everything was straight again. i just ant to make sure that if i do get the right head gaskets to try and remedy this, is that actually going to be okay?
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Old 10-21-2010, 10:42 AM   #5
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Is it 15min after initial start up or 15 of beating the motor?

Thicker head gasket will not solve the problem of blowing the gasket out. Might not be a bad idea to have another machine shop take a look. As this way you can have another professional analyze the work of the other shop to confirm that everything was done right, and if not they can give you a idea of what is going on.
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Old 10-21-2010, 10:44 AM   #6
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sorry if i didnt mention, but this is a turbo motor.. so under boost it blows them out
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Old 10-21-2010, 10:46 AM   #7
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If everything is perfect on the machining end of things, and the install is correctm maybe the gasket manufacture uses a poor material, bad batch, or just a poor design.

A head gasket is just a seal between 2 mating surfaces.
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Old 10-21-2010, 10:49 AM   #8
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i have used cometic every time. maybe i should try a different company, but im just not ready for disappointment from a maybe.
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Old 10-21-2010, 11:13 AM   #9
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Quote:
Originally Posted by EmaciatedCow View Post
i have used cometic every time. maybe i should try a different company, but im just not ready for disappointment from a maybe.
OEM gasket best gasket outer
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Old 10-21-2010, 11:20 AM   #10
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Cometic FTL.... OEM it up. But it probably doesn't help that you have Wiseco's (8.9:1 I imagine) and you had the block/heads decked. Your CR is probably quite high.
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Old 10-21-2010, 11:36 AM   #11
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O ring the block and be done with it. You're this far into it already, it's not much more money.
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Old 10-21-2010, 01:15 PM   #12
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Cometics like a VERY fine RA for the finish. Then they'll hold just fine. Can't use a crappy to deck on a subie running Cometics.

Try their fuzions (phusions, whatever) or get another gasket company or just o-ring...as mentioned above.
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Old 10-21-2010, 02:38 PM   #13
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advance the timing more.
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Old 10-21-2010, 03:06 PM   #14
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didn't you mention above something about the studs pulling out or something?you were not very clear about that and if the studs were starting to pull out of the block they definitely would not have the proper clamp force on the gskt.Who did the larger stud install?did they do it right?I would say it is not the gskt thats causing the issue and I have built a sleeved block where the pistons were about .005 above deck and just ran a .051 cometic and did not have a problem.Also is the tune in line for the motor having more compression?There are so many variables that could be causing this problem it is going to be really hard to diagnose without seeing the motor,the tune,anything involved.I hope this gives you some ideas on what to check--good luck.
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Old 10-21-2010, 03:37 PM   #15
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The cometic head gaskets suck. I went through three sets of them on my old turbo build until I learned my lesson and went OEM. The cometics only seal if the surfaces are basically brand new. So if you are trying to use 255 heads they have to have a very very fine surface if not new.

On my new build, I have the block O-ringed and will be trying some Cosworth HGs. See if they hold. If not, then back to oem.
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Old 10-21-2010, 04:16 PM   #16
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it was just the last set of gaskets that had the issue with the studs on so i dont think we can count the last super thick set of gaskets in all of this.

ive pretty much decided to start over with a new (to me) and get some cosworth head studs and just bore the block to 100mm. i just want to be done with all of this. its been too long
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Old 10-21-2010, 06:00 PM   #17
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why bore the block when you have a gasket problem?
were the head studs fully tightened into the block before the heads were bolted on?
you keep saying the block has been machined flat. what about the heads?

edited: i use the cosworth hg and have had no issues
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Old 10-21-2010, 06:03 PM   #18
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no i mean bore a new block
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Old 10-21-2010, 06:22 PM   #19
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bore a new block, whats the point. when you bore it you will be more likely to crack a cylinder wall.

do new OEM size pistons and have an extra thick coating put on the skirts. that way the machine shop can hone each hole for a specific piston.

and the heads? have they been checked or not?

edited: sorry just reread the OP about the heads being done too

Last edited by nhsilversti; 10-21-2010 at 06:31 PM.
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Old 10-21-2010, 06:25 PM   #20
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100mm is fine for alot of hp. yes the heads and block were both decked last round of gaskets
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Old 10-21-2010, 06:34 PM   #21
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Quote:
Originally Posted by nhsilversti View Post
bore a new block, whats the point. when you bore it you will be more likely to crack a cylinder wall.

do new OEM size pistons and have an extra thick coating put on the skirts. that way the machine shop can hone each hole for a specific piston.

and the heads? have they been checked or not?

edited: sorry just reread the OP about the heads being done too
he has iron sleeves
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Old 10-21-2010, 06:41 PM   #22
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Quote:
Originally Posted by EmaciatedCow View Post
it was just the last set of gaskets that had the issue with the studs on so i dont think we can count the last super thick set of gaskets in all of this.

ive pretty much decided to start over with a new (to me) and get some cosworth head studs and just bore the block to 100mm. i just want to be done with all of this. its been too long
Quote:
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he has iron sleeves
maybe i misunderstood his comment about getting a new block
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Old 10-22-2010, 11:37 AM   #23
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i was just told i was not allowed to put a stock block back in by a friend.. more news after the weekend


see everyone at the shootout!
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Old 10-25-2010, 05:22 PM   #24
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okay, so talked to jr this weekend. my motor is getting o-ringed this week.

**fingers crossed**
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Old 10-25-2010, 05:27 PM   #25
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Quote:
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okay, so talked to jr this weekend. my motor is getting o-ringed this week.

**fingers crossed**
Smart decision.
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