View Single Post
Old 08-07-2018, 04:33 PM   #1
Ol' Ron
Senior Member
 
Ol' Ron's Avatar
 
Join Date: May 2010
Location: Chester Vt
Posts: 8,842
Default Piston to head clearancing

I get this question allot, thought I just post this information for those that might not understand why this is a good practice.

Understanding why this is important will give you the reason to do it. Modern engines have a very hi compression ratio, and still run on regular gas. This is due to the very hi turbulence in the chamber just prior to ignition. This is done by an area called the Quench area. The Flathead doesn't have such an area, so we have to make one. Thus the .045/.050" piston to head clearance. I measure this with little alum balls I make from aluminum foil. A bout 1/2 3/8 in in diameter. I stick them in the area to be measured. Now if your not sure about this, have someone else help you. You must mill the head to get this number, which is usually just an area around the perimeter of the piston. I relieve the valve clearance at to top of the cylinder head with a small die grinder, so as not to remove to much material which would lower the CR. Doing this will not raise the CR very much, but cause a hi degree of turbulence in the chamber condensing the AF for better and complete combustion. Moer power, economy and better throttle responses. And for very little cost.
Ol' Ron is offline   Reply With Quote