The Ford Barn

38 coupe · 04-09-2023, 12:05 PM

Does anyone have experience on how thick factory head castings are above the piston?

Background:
Terry (caddilac512) recently made a tool to re-cut the dome in factory heads and showed his work in this thread. That got me to thinking, which can be dangerous. I have a Mercury crankshaft that has been offset ground to 4 1/8 stroke. The only pistons commonly available for that stroke are forged construction and for a large overbore. Cast pistons in a moderate overbore would require ordering custom pistons. I’m not excited about the idea of custom ordering pistons (I’m cheap). I don’t have a car that needs an engine at the moment, so I have time to plan. I also have a set of NOS +.030 Mercury pistons, a good set of 21A rods, and a worn standard bore 3 3/16" block that with luck will have no fatal cracks.

Pondering:
The re-doming thread got me pondering on the possibility of running 4” stroke pistons in a 4 1/8 stroke motor for 1/16 pop up (.0625”), and cutting the dome in a factory set of heads for .040 piston to head clearance. Does anyone know if there is enough material in a factory set of heads to pull this off?

04-09-2023, 12:05 PM	#1
38 coupe Senior Member Join Date: May 2010 Location: South Texas Posts: 2,135	Factory head casting thickness Does anyone have experience on how thick factory head castings are above the piston? Background: Terry (caddilac512) recently made a tool to re-cut the dome in factory heads and showed his work in this thread. That got me to thinking, which can be dangerous. I have a Mercury crankshaft that has been offset ground to 4 1/8 stroke. The only pistons commonly available for that stroke are forged construction and for a large overbore. Cast pistons in a moderate overbore would require ordering custom pistons. I’m not excited about the idea of custom ordering pistons (I’m cheap). I don’t have a car that needs an engine at the moment, so I have time to plan. I also have a set of NOS +.030 Mercury pistons, a good set of 21A rods, and a worn standard bore 3 3/16" block that with luck will have no fatal cracks. Pondering: The re-doming thread got me pondering on the possibility of running 4” stroke pistons in a 4 1/8 stroke motor for 1/16 pop up (.0625”), and cutting the dome in a factory set of heads for .040 piston to head clearance. Does anyone know if there is enough material in a factory set of heads to pull this off?