Leak around stud

[baileyem]

While running my engine at the dock, yesterday, I spotted a problem that only occurs when I run the rpm to 1500 and above with the forward gear engaged. The problem does not occur at lower engine speeds.

There is a leak around a head stud between #2 and #3 cylinders. Water will begin emerging and run into #3 sparkplug well and procede to boil. As soon as I lower the throttle setting, the leak stops and the residual water yurns to steam and disappears.
I checked the compression. The results were, 1-4: 86; 87; 100; 104.
The engine runs well, idles well, and will push the boat at 7 mph at 1750 rpm.
The engine is an early model A-4 (1966).
My questions are: do I have to replace the head gasket or can I simply reseal the stud somehow?
Do I have to do it now, or can I wait 'til the end of the season?
Any other options?

Mike

[Don Moyer]

Mike,

If you can remove the stud, you can reinstall it using a good tenacious sealer like Permatex Aviation Brand sealer or JB Weld on the lower. If you can't get the stud out, you could put Permatex Aviation Brand sealer between the stud and the head, allow the sealer to set up overnight, and then add a little fresh sealer under the nut and on the upper threads. I'd limit the torque on the nut to 30 or 32 foot-pounds on this stud.

Don

[baileyem]

Thanks Don. I'll try that and hope that I don't break the stud while I'm at it.

Mike

[baileyem]

OK, I worked for a day and a half trying to remove the stud, but it wouldn't budge. I used PB Blaster, the double-nut method , wrenching, tapping, heating, and threatening. Nothing worked. I applied sealer between the stud and the head , let it set, and torqued it down.
It still leaks. Not as much, but it does.
Should I now remove the head to remove the stud, or simply break it off and drill it out with one of MM's stud replacement kits?

Mike

[Don Moyer]

Mike,

Did you fill the annular space between the stud and the head using Permatex Aviation brand sealer? If not, I would still try that as a quick fix instead of the sealer you were using. If you did use Permatex Aviation Brand sealer, I'd top the annular space off one more time and give it another try. As long as you're able to torque the nut to at least 30 foot-pounds, you don't have a structural problem, only a water leak (like under your kitchen sink).

I can't imagine your being able to break the stud using the two-nut approach, so if all attempts to seal fail, you may opt to spring for one of our stud removing tools to apply a bit more muscle in removing the stud so you can seal the lower threads more directly. This approach could easily save you a day or two of labor and the cost of the repair stud kit.

Don

[baileyem]

Thanks for the reply, Don. I will give it another try. I haven't been able to find any Aviation Brand Permatex. That is why I used something else.