Why are my Air Filter Bolts Drilled for Wiring?

[Michael Pawelek]

I cannot figure out why the heads on these bolts are drilled. Are they really supposed to be wired or did someone take them from another place on the 356?

[Adam Wright]

It's always an option. I was wiring this week, the bottom one came out ok. In my defense the last time I did safety wiring was 30 years ago on my dad's plane.

[Wes Bender]

I hate to tell you Adam, but you need to do it over. Remember which way the bolts tighten and have the wire pulling in that direction.

Unless there is a reason for one long stretch, I would wire the two on each end together (from right side of top bolt to left side of bottom) and forget the length from side to side. If you want to use one long twisted length for all four, run it in a box shape, not diagonally.

(Unless they are left hand thread.....and then I am hopelessly confused.)

[Mike Wilson]

Michael, I've seen those as well. Maybe for the Super 90 filters. Not the right length for Carrera filters, right?

Mike

[Michael Pawelek]

Michael, I've seen those as well. Maybe for the Super 90 filters. Not the right length for Carrera filters, right?

Mike

Mike, I have no idea what else they may fit.
I am brand new to the 356 and have never even seen another 356 in person. This is all new to me. I just thought it odd that a air filter needed to be wired. It’s not like they are flying off the carburetors constantly!

[Wes Bender]

I think the bolts would look cool safety-wired. A little more work when cleaning filters or balancing carbs, but I'd do it. If you decide to do it though, do them correctly.

[David Jones]

If you're going to do that then the first thing you need to buy after the locking wire is a pair of locking wire pliers. Using locking wire is a PITA without.

[Mike Wilson]

These make safety wiring MUCH easier. Available from many vendors,

Mike

[Jacques Lefriant]

Hi
Back in the day they did not do much twisting of the wire just the final twist.
j

[Wes Bender]

A single strand of wire is what is usually used on parts during storage, transport etc. Cars aren't as critical as aircraft so twisted wire would normally not be necessary, but it sure looks better.

[Don Gale]

Anything subject to vibration will be best served with safety wire. I have cross-drilled and sold countless 100's of BMW camshaft oil spraybar bolts. More often than not, when scavenging parts at U-Pull-it, I find banjo bolts completely backed out and laying in the oil return galleys. Anything that relies on bolting a soft or deformable part such as an oil tube or air cleaner that cannot be tightened without deforming the part, should be safety wired. Some things are more critical than others, for example, the front brake backing plates are safety wired from the factory and explicitly shown in the repair manual. I for one have suffered fuel leaks from the main/idle jet cover on Zenith carbs and from now on, will ALWAYS safety wire them.

[John Clarke]

Hi Wes
"Do It Over Adam"
I love It.
What do You Think Adam
Jay

[Wes Bender]

Hi Jay - Old aircraft mechanics cringe when they see incorrect safety wiring. In Adam's defense, I think he was just playing around with it. The finished product will probably be up to the same high standard as the rest of that fine machine.

[Adam Wright]

Hi Jay - Old aircraft mechanics cringe when they see incorrect safety wiring. In Adam's defense, I think he was just playing around with it. The finished product will probably be up to the same high standard as the rest of that fine machine.

Yes, 1st try in 30 years, it will take a few tries to get it where I want it.

[Wes Bender]

Hi Adam, the twists are in the correct direction, left over right. The number of turns should be 6 - 8 per inch. Pull it tight and, as previously mentioned, arranged so that pulling on it would try to tighten the bolts. (On the B-47, there were places where I could only see with an inspection mirror, but had to safety wire fasteners while reaching around from the back. And, they had to pass a quality control inspection too.)