I have installed the pistons from my "broken crankshaft" 4A-GE into a 7A-FE that I am reconditioning. The intent of this mod was to increase the compression, to see if this might be an easy way to increase the power output of the 7A-FE.
The result is an inteference engine.
The 4A-GE pistons and pins fit quite nicely on the 7A-FE rods.
With the timing belt installed (and timed) everything clears. I did not have putty to measure how close the pistons and valves come to each other, but with the timing belt off, there is contact.
Both piston crowns come up to about the same level in the cylinder. The 7A piston has a recess in the top, whereas the 4A-GE piston has a slight dome with valve reliefs cut in it.
The difference in the angle at which the valves are set in the heads means that the narrower included angle of the 7A valves cause them to contact a part of the 4A-GE piston dome where there is no relief cut into it.
This installation was with the 7A head gasket. Maybe with the 4A head gasket it might clear, since that is a thicker gasket.
Unfortunately, that will bring the compression back down a bit, making this a questionable exercise, since I have no idea how much the increase might be to begin with.
The result is an inteference engine.
The 4A-GE pistons and pins fit quite nicely on the 7A-FE rods.
With the timing belt installed (and timed) everything clears. I did not have putty to measure how close the pistons and valves come to each other, but with the timing belt off, there is contact.
Both piston crowns come up to about the same level in the cylinder. The 7A piston has a recess in the top, whereas the 4A-GE piston has a slight dome with valve reliefs cut in it.
The difference in the angle at which the valves are set in the heads means that the narrower included angle of the 7A valves cause them to contact a part of the 4A-GE piston dome where there is no relief cut into it.
This installation was with the 7A head gasket. Maybe with the 4A head gasket it might clear, since that is a thicker gasket.
Unfortunately, that will bring the compression back down a bit, making this a questionable exercise, since I have no idea how much the increase might be to begin with.