Just trying to learn here so please dont kill me. So how do you get higher compression. Is it in the pistons you buy or the head work or both. Just looking for some more info so I can understand how the motor works. Read post about flat top and dome top.
Thanks

 

Both can raise compression. Milling heads and making combustion chamber smaller can really raise it quickly, but so can domed pistons.

 

Anything that makes the area in the combustion chamber smaller add to compression. You can mill the heads to bump, use a thinner head gasket, use a domed piston etc.....Than you factor in the cam you using and there is another can or worms....lol

 

Also the milling the cylinders to 0 out the deck height , if the pistons are down in the hole. Thinner head gasket. Also a big bore will raise compression as you are now moving bigger pistons in relationship to the chambers...more compression. Also cam closing events will alter cranking pressure which is what the compression your motor sees while running, later cam closing bleeds off cranking pressure. Go to Big Boyz web site ,the calculators he has on there will show this in #'s. Kinda cool.

 

All of the above is correct. If you are planning a build you need to figure out where you want the power, i.e., the rpm range where you spend most of your time on the bike. Then select a cam with a profile to deliver the power in the desired rpm range. Most head porters can tell you what compression will produce the "sweet spot" for a particular cam and that's your target.

It is usually more desireable and less complicated to achieve the desired compression with flat top pistons because of the TC bathtub head design with two quench/squish areas. Once you start to introduce a domed piston into the combustion chamber, the quench/squish areas become more difficult to define.

You have probably heard all this before, so apologies if I have posted facts that you are already aware of.