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30% Nitro- Do I Need A Head Shim?

Old 10-27-2006, 03:14 PM
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swerv512
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Default 30% Nitro- Do I Need A Head Shim?

just like the question says....
last weekend i ran out of 20% nitro in my OS12tz 3 port so i decided to run the 30% nitro that was available. i ran about 10 or so tanks in my touring car and i can say that i did notice an increase in engine power and response. however i didnt add a head shim (as i've been told to do). will this damage my engine? can i continue to run 30% in my 12tz without adding a head shim? if a head shim is required, what thickness do i need to use? are there any obvious signs that a head shim should be used? thanks.
Old 10-30-2006, 10:56 AM
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Bax
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Default RE: 30% Nitro- Do I Need A Head Shim?

If you're getting detonation, then you need to add a head gasket to reduce the compression. You can tell if the engine's detonating because you'll get a "frying egg" sound in the exhaust note at full throttle. This can sometimes be masked by the type of exhaust system.

Another way to check for detonation is to examine the top of the piston. If you're getting an eroded ring in the center of the piston, you're getting detonation. You can start out by just adding another cylinder head gasket. If you get too much power loss after lowering the compression, then use a second gasket 1/2 the thickness of the original. You may have to rub a gasket on a stone to thin it down if you need an "in-between" size.

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