> Terbo Speghetti wrote:
> -------------------------------------------------------
> > James P wrote:
>
> > -------------------------------------------------------
>
> >
>
> > Deleting a head gasket does lower compression when you more than make
> up
>
> > for it with a thicker base shim.
>
> It lowers compression in the bottom end, yes. But raises it in the top
> end.
No it does not.
When you shim the base 1mm you lift both the cylinder and head attached to it 1mm.
That increases the combustion chamber volume by 1 mm. Lowering compression.
If you delete the < 0.5 mm head gasket, you gain back some of what was lost (compression) by decreasing combustion chamber volume, but you are still net lower compression than what you started.
The only way to raise compression in this scenario would be to shave the head by more distance than the spacer width. Like: adding a 1 mm base shim and shaving 1.25 mm from the head.
Then you have decreased the volume of the combustion chamber.
People do that, but I prefer to raise port timing and LOWER compression by shimming the base and deleting the head gasket without shaving the head the same amount as the shim width.
Also, no head gasket = no blown head gasket. Which I find to be a good upgrade for reliability.
Does that make my point clearer? Sometimes I assume what I’m typing will be read a certain way and then get sucker punched by a weird take.