4MV Power Piston Pin Repair
Posted: Sun Apr 11, 2021 4:32 pm
Decided to resurrect my first Qjet, a 7042210 Holley Reman. Yeah, I didn't know better 25 years ago. Of course, they cut the power piston pin. So I wanted to see if I could fix the pin issue.
After trying to pull it out, I came up with the following way to fix it. Sorry, didn't think to take pictures, but its fairly straightforward:
Pull off the metering rod holder with a pair of needle nose pliers. It pulls right off.
Remove the power piston retaining ring.
Using a 5/64" drill bit, drill down till you hit the steel pin or the cavity it sits in.
Using a 4 penny finish nail drive the old pin out.
The pin is 0.090" diameter, same size as a 6 penny finish nail.
Cut off the pointed end of the nail and file it flat a put a little chamfer on it.
Insert the nail with new end into the hole on the bottom of the power piston where the old pin stuck out.
Drive the nail in about 3/16". It should be plenty tight.
Now measure 0.300" from the bottom of the power piston and make a mark on the nail sticking out.
Cut on the mark, file flat and put a slight chamfer.
Put a new retainer on the power piston, insert the hanger arm assembly back on.
Done. Takes about 20-30 min. Good rainy day project.
After trying to pull it out, I came up with the following way to fix it. Sorry, didn't think to take pictures, but its fairly straightforward:
Pull off the metering rod holder with a pair of needle nose pliers. It pulls right off.
Remove the power piston retaining ring.
Using a 5/64" drill bit, drill down till you hit the steel pin or the cavity it sits in.
Using a 4 penny finish nail drive the old pin out.
The pin is 0.090" diameter, same size as a 6 penny finish nail.
Cut off the pointed end of the nail and file it flat a put a little chamfer on it.
Insert the nail with new end into the hole on the bottom of the power piston where the old pin stuck out.
Drive the nail in about 3/16". It should be plenty tight.
Now measure 0.300" from the bottom of the power piston and make a mark on the nail sticking out.
Cut on the mark, file flat and put a slight chamfer.
Put a new retainer on the power piston, insert the hanger arm assembly back on.
Done. Takes about 20-30 min. Good rainy day project.