Online Community of Zenith Builders and Flyers
Ever have that horrible sinking feeling in your stomach when you keep torquing a head stud and the torque never goes up? I have! I did a test run last month after I got my engine installed in the fusilage. Then I adjusted my carb, retorqued all the head studs, set the lifters with the engine running, reset the timing and changed the break-in oil / filter. On retorquing the head, the upper left stud on the number one cylinder pulled out - OH CRAP.
I looked at an extra case that I have and found that this stud does NOT communicate into the crankcase. My first bit of luck! I ordered a Time-Sert kit and with a bit of modification was able to replace the stud without hardly any disassembly. The only thing I had to remove was the baffle between the first cylinder and the distributor - two bolts.
Important points that I learned-
Grind down the ends of the Time-Sert tools - drill / reamer / tap / setter to fit in a 1/4" drive extension. I used a 3" and 6" extension.
Drill out the head stud hole in the head to let the extensions pass thru - 31/64ths. If I ground down the socket end of the extensions it could of been less, just hate ruining tools.
Grind down the reamer (significantly) to clear the cylinder. It only cuts the recess for the head of the time-sert. There's enough room with the cylinder in place, but barely.
Just use a good tap t-wretch on the extension, aluminum is soft and very easy to cut with these tools.
Chase the threads on the stud with a good 3/8 - 16 die opened up as much as possible for a good tight fit.
If I had to do it again (without modifying the tools) it would take less than a half hour to replace a pulled stud. I'm so glad I did not have to spend days disassembling everything!
Couple other install pics.
Thanks for the explanation and photos. I'm still building but this could be great to know, when or if the time comes.
What torque value are you using for the heads?
30 with the old Craftsman TR