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Old 09-14-2006, 01:40 PM   #1
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Raising the compression ratio.......?

I am going to be removing my head soon to install my cams and I was wondering if I put a thinner head gasket would that raise the compression ratio enough to gain some power?
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Old 09-14-2006, 01:55 PM   #2
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More importantly... would you run into interference issues?
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Old 09-14-2006, 02:39 PM   #3
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You don't need to remove the head to install cams
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Old 09-14-2006, 03:16 PM   #4
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Old 09-14-2006, 03:35 PM   #5
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I think you should let a tech do that for you.
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Old 09-14-2006, 03:54 PM   #6
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Alright, so will installing a thinner head gasket raise compression enough to where it would be worth it? Noticeable gain...
Also removing the head makes the install easier, http://www.pelicanparts.com/bmw/tech...ft-removal.htm
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Old 09-14-2006, 04:26 PM   #7
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And the relevant portion from the post:

Quote:
Originally Posted by Samir View Post
Why did you replace the head gasket? Did you install a thinner one? For higher compression ratio... once you do that, you're retarding your cam timing, which (in a Honda at least) you woudl tune w/ the adj. timing gears.

Not sure what you mean by "why", but anytime you remove a head you cannot reuse the stock gasket. On Nick's car, we installed a new BMW gasket designed for a resurfaced head. No intentional raising of compression was done...there is only one way to properly alter compression and this is through piston modification. Monkeying with compression ratios through other means (milling, head gaskets, etc.) will only upset the squish volume, which is absolutely sacred...people who choose to upset this squish volume usually have a nice "pinging" sound coming from their engine . It is the strongest deterrent to detonation by pushing the intake charge towards the center of the chamber as the piston makes it's upswing towards TDC (keeps charge turbulence high and helps eliminate end gas as well).
In addition, once you start overmilling heads to bump up compression you risk running into all sorts of other problems such as increased combustion temperatures and valve clearance iussues.
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Old 09-14-2006, 05:04 PM   #8
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Quote:
Originally Posted by AS007 View Post
I am going to be removing my head soon to install my cams and I was wondering if I put a thinner head gasket would that raise the compression ratio enough to gain some power?
Any time compression is increased power is always increased, but on varying levels, I mean adding .3 to your compression ratios isnt going to be an extremely large difference, a noticable difference, but not huge. Also with a thinner headgasket compression is raised on varying levels once again(depend on the thickness of the headgasket), however then things that were mentioned further down this thread come into account. The best way of increasing compression is by changing the pistions out. If you're changing pistons then you'll most likely have to change the rods too, as I'm not sure of how many companies make high comp pistons that fit onto the stock rod. It's always better to do both, strengthening the bottom end always helps out!
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Old 09-14-2006, 05:11 PM   #9
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Ok, so it's not a good idea then. Thanks for the info!
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Old 09-14-2006, 05:23 PM   #10
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You can do it if you like, however if you read the post where txzhp04 is quoting samir, he clearly points out why it's better to add compression via pistions as opposed to using a headgasket.
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Old 09-15-2006, 01:59 AM   #11
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Pistons are a better choice for lowering compression but a well designed multi-facet gasket can acheive results if you are looking for just small drop in compression. Check out the many successful E36 turbo kits on aftermarket gaskets, studs, and stock pistons. All this while maintaining squish control.
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Old 09-15-2006, 06:46 AM   #12
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Pistons are a better choice for lowering compression but a well designed multi-facet gasket can acheive results if you are looking for just small drop in compression. Check out the many successful E36 turbo kits on aftermarket gaskets, studs, and stock pistons. All this while maintaining squish control.
Yes, but he's looking to increase hp by raising compression....
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Old 09-15-2006, 12:22 PM   #13
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I understand that. What I am saying is that small *lower* compression changes can be accomplished with a well-made gasket, studs, etc. The head gasket is pretty thin in stock form and I would think it is nearly impossible to get a strong enough format to make a *thinner* version to raise compression. The same goes for milling the heads.

You are then looking at pistons and with the valve clearance in our interference engines, I think that is out as well. The best you could probably aim for is to match the mid 11s of the S54 and still not have the displacement or redline.

A lot of money, time, work, and reliability goes right down the drain if you do this wrong. You likely have other, better options to reach your goals.
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Old 09-15-2006, 12:30 PM   #14
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I understand that. What I am saying is that small *lower* compression changes can be accomplished with a well-made gasket, studs, etc. The head gasket is pretty thin in stock form and I would think it is nearly impossible to get a strong enough format to make a *thinner* version to raise compression. The same goes for milling the heads.

You are then looking at pistons and with the valve clearance in our interference engines, I think that is out as well. The best you could probably aim for is to match the mid 11s of the S54 and still not have the displacement or redline.

A lot of money, time, work, and reliability goes right down the drain if you do this wrong. You likely have other, better options to reach your goals.

Ah, I see what you're saying now... didn't quite get all that from your previous post.
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Old 09-15-2006, 06:50 PM   #15
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VAC sells 11:1 piston packages for $1000
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Old 09-18-2006, 05:45 PM   #16
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not worth it, I would prob lower compression, and do fi cams and then blower (turbo or sc)
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