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A good number of you have fitted metal head gaskets in varying thickness to your RB25DET engines, 1.2mm seems quite poular. I know this allows you to run higher boost pressure from the turbo. What does the head gasket take the compression ratio down to? Why not just fit lower compression pistons when rebuilding the engine? Or id this done as metal gasket give slightly better sealing characteristics?

Cheers
 

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"A Skyline with 4 doors?"
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The metal head gasket is not done for the compression difference it creates, which is tiny. The extra thickness it provides is just and added bonus. The reason is to strengthen your engines ability to run high boost. And to help prevent blowing a head gasket from the previous or a sudden pressure spike or detonation.

Hey, ignore the first couple of sentences, I was mistaken on that thought.
 
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GTES-t said:
The reason is to strengthen your engines ability to run high boost.
By lowering the compression ratio. If it didn`t make much difference to that as you say then surely pistons & crank bearings would be in trouble??

Theres loads on SDU about this. I suggest doing a search as i just did. Got 6 pages come up after typing in compression ratio to the search.
 

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M's Factory
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to a point it comes back to detonation level, but realistically the phrase its always safer than to be sorry.

Cost the Headgasket Vs cost of Buying potential, exhaust/inlet valvue and piston replacement should you get a bang ?????
 
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