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!

Views: 589


Reply to This

Replies to This Discussion

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.

Hi Mark,

What torque value are you using for the heads?


30 with the old Craftsman TR


New from Zenith:

Zenith Planes For Sale 

Classified listing for buying or selling your Zenith building or flying related stuff...


Weather Maps

Custom Instrument Panels
for your Zenith

Custom instrument panels are now available directly from Zenith Aircraft Company exclusively for Zenith builders and owners. Pre-cut panel, power distribution panel, Approach Fast Stack harnesses, Dynon and Garmin avionics, and more.

Custom Upholstery Kits for your Zenith Aircraft:

Zenith Vinyl Upholstery Kits

Zenith Apparel from EAA:

Zenair Floats

Flying On Your Own Wings:
A Complete Guide to Understanding Light Airplane Design, by Chris Heintz

Builder & Pilot Supplies:

How to videos from HomebuiltHELP.com

Developed specifically for Zenith builders (by a builder) these videos on DVD are a great help in building your own kit plane by providing practical hands-on construction information. Visit HomebuiltHelp.com for the latest DVD titles.

Aircraft Insurance:


West Coast USA:

Pro Builder Assistance:


Transition training:

Golden Eagle Aviation

Pianosa Flying Farm

Aircraft Spruce & Specialty for all your building and pilot supplies!

© 2020   Created by Zenith.Aero.   Powered by

Badges  |  Report an Issue  |  Terms of Service