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Old 08-07-2002, 12:08 AM   #1 (permalink)
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How To raise compression ratio, w/o piston

How To raise compression ratio, w/o piston. I'm talking about gasket like the spoon one. Can i use like 3 OEM head gasket to accomplish this.
How would i raise or lower compression w/o piston?
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Old 08-07-2002, 12:21 AM   #2 (permalink)
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3 oem gaskets would lower compression, if that is even possible. either use a thinner gasket, which i wouldn't recommend, or mill your head.
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Old 08-07-2002, 12:22 AM   #3 (permalink)
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Well, the best way is going to be getting new pistons. Basically, adding more headgaskets will lower your compression, and your odds of getting blowby w/ more than one gasket greatly increases. Do it right and get different pistons. I don't know if you can do this with a 4 stroke motor, but on our race sleds we cut the heads. Basically we mill some of the bottom of the head off bringing the piston closer to the top of the combustion chamber. But for the money I would get pistons, that way your motor is fresh.
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Old 08-07-2002, 07:27 AM   #4 (permalink)
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I'd want to know why you want to raise compression. The Type S or similar pistons wont' change it much (from a standpoint of power), and to change it to where you would notice a difference, you would probably end up detonating and limiting yourself w/o cams and other mods.

You can mill the head or the deck but that will dick up the cam timing... you would need gears to get that right.
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Old 08-07-2002, 07:40 AM   #5 (permalink)
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Using a thinner head gasket will also retard the cam timing.

The only options to raising the CR without pistons would be to deck the block, mill the head, use a thinner head gasket, or weld up the combustion chambers.

If you're going to do it, do it right, as the higher you raise your static CR, the narrower the tuning window is avoid detonation (everything else being equal).
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Old 08-07-2002, 08:16 AM   #6 (permalink)
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echo...
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Old 08-07-2002, 09:43 AM   #7 (permalink)
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well i was just wondering and not sure if adding more then a layers of gasket would lower or raise ompression. The reason why i ask is b/c my friend ususe a b20/vtec setup and he is using 3 layer of OEM gasket. i remember asking him what is his compression he told me 12:7 and he runs on 93 octane so i wonder how that is possible and he told me tunning makes it possible, even so i dont think tunning can makes 12:7 running on 93 octane work

Maybe 93 and octane booster, right?
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Old 08-07-2002, 10:02 AM   #8 (permalink)
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Well, detonation and pre-ignition resistance depends on many things other than CR; cylinder temps, piston design, combustion chamber shape, fuel temp, air temp, etc. etc. It could be possible to get an engine to run 12:1 CR on pump gas without too much trouble, given the right tools to do the job.
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Old 08-07-2002, 10:28 AM   #9 (permalink)
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Along the same lines, w/o someone like Endyn doing a complete engine build, it will be something of a crapshoot to end up with a motor that won't detonate.

Also keep in mind that if you plan to run anything higher than 93 octane (via booster, race gas, whatever) that you will need to budget for O2 sensors and plugs as you will need to replace them regularly. Also plan on a workaround to run w/o a cat unless you budget for those as well.

Also, for compression like that, I would plan on a standalone ECU if you want to be reliable.
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Old 08-07-2002, 04:07 PM   #10 (permalink)
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I don't really like the idea of milling the head, if something goes wrong on down the line it gives you less to work with. For a slight (like .2-.3) you can get some high compression valves like what Skunk2 has. I wouldn't reccomend going over 11:1 on a street car (on pump octane), the timing would have to be retarded so far to avoid detonation that your fuel milage and power will suffer.
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Old 08-07-2002, 05:46 PM   #11 (permalink)
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the spoon head gasket
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