Leaking Stud/Noise-Accessory Drive

[Simon]

Don,
Now that the engine has a few hours dockside after the rebuild, a couple of issues have developed. The first is a leaking stud. It's a centre stud immediately aft and slightly to the left of the #1 spark plug. When the engine is running, I can see a small amount of water(I presume) percolating up from the threads on top of the nut. The amount is not much but I believe is cause for concern. I seem to recall in a previous post or guess log that the stud will have to be removed and resealed. My question is: should I attempt this fix first to see if it will do the trick or do I contemplate a repair stud now? The second issue is a tapping like sound which I believe emitts from the accessory drive. The sound is apparant at different RPM ranges, comes and goes, and sounds the same regardless the RPM. Gear alignment at distributor shaft or idler gear bushing? Bushing was replaced at rebuild. The alternator belt maybe a little loose which maybe a contributing factor. The alternator is at it's max adjustment as it is. Will look for a slightly smaller belt to tighten things up which may help or make things worse. Other than getting a different alternator bracket, I will also try to drill out the slot to give me another 1/2 inch adjustment. I will monitor the noise for a few runs, and if it doesn't go away or if it gets worse I'll remove the accessory drive and investigate idler gear. It maybe time for a rebuilt accessory drive. An off topic point: I am preparing to install your oil/temp alarm system. Can I not connect the leads to the present oil/temp sending units or are they manufactured in such a way that this simply won't work? Thanks Simon

[Don Moyer]

Simon,

Starting with the most conservative fix for the stud, we have sealed several studs by removing the nut and pouring Permatex Aviation Brand sealer between the stud and the head, allowing it to set up for a couple hours (or overnight), and then re-torquing the nut. In other words, there's no need to assume just yet that the threads have failed. All you really have to do at this point is to keep the stud from leaking. You could also use JB Weld instead of the Permatex.

If the stud should pull out on re-torquing, you can use a 7/16" repair stud.

The tapping noise is probably caused by the big idler gear slapping back and forth against its friction washer, but an accessory drive bearing can contribute to that process. We have solved several disconcerting tapping episodes by simply switching accessory drives.

You cannot use the temp/oil pressure alarm system with your current sending units. The units that come with the alarm system are switching devices while the sending units used with your gauges are attenuating devices, meaning that they vary the resistance in the gauge circuit to give the appropriate reading on the gauge.

Regards,

[Don Moyer]

Greetings,

I had an interesting note from our ever vigilant Webmaster (Bill) the other day which caused me to slow down and reflect on one of the more important developments of the twentieth century - Permatex Aviation Brand gasket sealer. Bill's note was in reference to my answer to Simon's question regarding a leaky head stud. First Bill's note:

"The info on the Permatex product in your note below (the one to Simon) apparently does not match the image. Is it the wrong image, or are you referring to this product by the wrong name, and it is mis-named in the online catalog?"

It's the correct image and the correct product, Bill. This wonderful Permatex product is so old that it has had several names coined around it. When I was 12 years old (circa 1947) and starting to work in a local garage, the old-timers who would yell at me to fetch this and that, called it simply "Permatex", probably because it was about the only product that Permatex made at that time.

Some years later, Permatex began marketing a few other products so I was at risk of bringing the wrong thing when the old-timers yelled, or worse, applying the wrong product to gaskets, so they/we began calling the stuff in the can "aviation brand", which I never did quite understand because I don't know that it was ever used much on airplanes.

If you look closely at the photo in our catalog (product number: OHSP_04_80) you can see (though barely) the words "AVIATION BRAND" just above the words "FORM-A-GASKET". Thankfully, only a few old-timers ever yelled "Bring me the FORM-A-GASKET", or we'd have to contend with yet another name.

Whatever we end up calling it, "Permatex FORM-A-GASKET Aviation Brand Sealant Liquid" has a quality about it that no other sealer seems to have ever duplicated, which is all the more amazing because it preceded the formation of NASA which spawned many good products later in the same century. It is extremely tenacious (meaning that you don't want to have it fall on any surface unintentionally), and it's impervious to almost any cleaning agent that I've ever discovered once it has set up.

If you don't already have a container of MMI product number OHSP_04_80 in your tool box, I recommend that you include it in your next order. You never know when it will be just the right and perfect sealer for some tough job (like a leaky head stud).

Here (finally) is one more tip from my mentors of the 1940's. When your Permatex Aviation Brand arrives (if that's what you end up calling it), remove the top and allow the contents to "season" for at least half a day. When new, it tends to be a bit too thin to suit most old professional motor-heads.

Don

[Simon]

Leaking Stud/Noisy Accessory Drive

Don,
I went ahead with the conservative fix and will report back later this weekend on the results. Although, I don't think this will "fix" the problem but will merely contain the leak to between the block and the top of the head which I suppose will be visually satisfying. I was very tempted to remove the stud and use a thread sealer to stop the leak at the source. What I can assume with the conservative fix, is that, water between the block and stud nut is not an issue to worry about. Moving on to the problem with the accessory drive, is it possible that the drive is not getting enough oil where it is needed? I don't know the angle but the engine has quite a steep angle of attack. The reason I ask is that I installed the Extension Dip Stick Kit and as a result there may not be enough oil in the engine. The old dip stick was the rod type which was very difficult to read at the best of times especially if the oil was fresh. Therefore the "full" marks may not match from one stick to the other. I will have to experiment. In your experience, will my oil pressure reading vary significantly if the engine had too much oil or not enough? My "S.W.A.G"(scientific wild ass guess) tells me no.
Anxious to hank on the sails! Your advice is truly appreciated. Tks

[Don Moyer]

Simon,

It's true that sealing a leaky stud just above the lower threads is second best to sealing the threads themselves, but not by very much. I would estimate that 60% of the studs we observe during our rebuilding operation have evidence of water collecting above the lower threads, and there were no serious consequences. If you installed fresh water cooling on your engine, stopping the leak is more than visually satisfying; it will also prevent the loss of antifreeze and permit you to motor around the world should you desire to do so.

The best way to positively determine if your accessory drive is making a noise is to wedge a short piece of 1 by 4 wood against the pulley and apply a moderate pressure. If the accessory drive bearing is making the noise, the noise should change very noticeably as you apply a side load to the pulley.

You're correct regarding the oil level having no effect on oil pressure, unless of course it drops to below a quart and a half or so, in which case the oil pump will cavitate.

Best regards,

Don