Mark Whatley wrote this in 2006. Can anyone help me understand what Mark is saying about the trade off between using the ‘75 (“early”) head versus the “later” (years?) head to achieve higher compression?
I have a ‘75 2F I’m looking at rebuilding and I’m wondering if this comment from Mark suggests that I should consider replacing the domed pistons with flat head pistons and using a later model head “milled to achieve higher compression”? Is he suggesting using the domed pistons with the later model head and milling it so they don’t contact and to create a tight combustion chamber?
“Flat top pistons with closed (quench) chamber heads is a more effecient setup that domes and open chamber heads for the type of rpm and flow rates that you will see in a 2F. Any 2F.
If you run flat tops in the open chamber head, compression drops a lot. Bad thing. If you run domes in the closed chamber head, the piston and the head try to occupy the same space at TDC. Worse thing.
If you want to run the earlier head, mill it to reduce the volume of the chamber to bring compression back up some. In the real world (as opposed to the dyno) you will never notice an difference in power or economy over the later head with this approach. But if you start with the later head and mill it too, you can attain higher compression.
Mark...”
I have a ‘75 2F I’m looking at rebuilding and I’m wondering if this comment from Mark suggests that I should consider replacing the domed pistons with flat head pistons and using a later model head “milled to achieve higher compression”? Is he suggesting using the domed pistons with the later model head and milling it so they don’t contact and to create a tight combustion chamber?
“Flat top pistons with closed (quench) chamber heads is a more effecient setup that domes and open chamber heads for the type of rpm and flow rates that you will see in a 2F. Any 2F.
If you run flat tops in the open chamber head, compression drops a lot. Bad thing. If you run domes in the closed chamber head, the piston and the head try to occupy the same space at TDC. Worse thing.
If you want to run the earlier head, mill it to reduce the volume of the chamber to bring compression back up some. In the real world (as opposed to the dyno) you will never notice an difference in power or economy over the later head with this approach. But if you start with the later head and mill it too, you can attain higher compression.
Mark...”