1. ## How much fudging can be done with a head gasket

Is there a general rule of thumb for fudging with a head gasket to decrease compression?

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3. not really, just like having the piston down in the bore more. Of course by- by quench area, and thats not good for power or detonation.

But yeah if you slapped a .100 thick gasket in there it would drop it quite a bit.

4. Jsut do the math...

If you run .125 more in head gasket, the combustion chamber gets that much larger.

The combustion chamber quench area comes into play right away.

Have you considered palying with cam timing also?

How much C/R are we talking about reducing? I have done one point with gaskets, that is about all I felt comfortable with....(went from 11.5:1 to 10.5:1). I used copper gaskets to achieve it.

GT

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6. Originally Posted by probablecause
Is there a general rule of thumb for fudging with a head gasket to decrease compression?
There is a general rule of thumb.... ....but it's wrong!

The amount of static compression change will vary depending on what you're at right now (and the bore to stroke ratio).

For example if you're got a 7.5:1 engine, a few thousands here or there won't change hardly anything. If you're got a 14:1 engine a few thou can make or break you.

You have to know everything to be able to calculate ratios but here's a simple app that will show you what a gasket change will do.

http://users.erols.com/srweiss/calccr.htm

7. Originally Posted by probablecause
Is there a general rule of thumb for fudging with a head gasket to decrease compression?

If I recall with my engine with a 66cc chamber (4.6 x 4.25 )the difference from a .040 gasket vs a .050 gasket is .3 points from 12.3 down to 12.0 those are " ball-park" numbers.

Hope it helps you.

Sleeper CP

8. just go here http://www.kb-silvolite.com/calc.php?action=comp and keep changing the gasket thickness until you get where you what to be. Word of advice though, as you lower the compression this way, the detonation factor goes down due to lower compression, but goes up do to lack of quench. Its a two sided sword.

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9. Originally Posted by probablecause
Is there a general rule of thumb for fudging with a head gasket to decrease compression?
More info plz. Why do you want to lower compression? You can get away with much more in our world with an entire lake for a radiator.
But yes you can lower compression with thicker gaskets, not the correct way but it can be done. If you need to cut much you will have to use copper gaskets and you can get them THICK. With more info you will get more accurate and relevent answers.

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