Grounding to the engine - what is this threaded location on the engine?

[Saville]

So yesterday I had the cowling off and was studying how the Reiff Pre-heater installation might be done on the O-360.

I noticed in the instructions that they grounded the wiring harness to the crankcase bolt that also has the engine lift ring.

I really would rather not screw around with crankcase bolts if I didn't have to.

But I noticed a threaded location just below that lift ring, in between the two cylinders.:



The Reiff harness is laying on the top of the crankcase and is threaded through the lift ring.

What is that threaded location for? There's one on both sides of the engine.

Also, at the right of the photo is a support for the forward part of the baffling. Looks like aluminium. The Reiff harness connectors are in front of it. Is that conductive enough to serve as an engine ground?


Thanks!

[BillL]

Originally Posted by Saville

So yesterday I had the cowling off and was studying how the Reiff Pre-heater installation might be done on the O-360.

I noticed in the instructions that they grounded the wiring harness to the crankcase bolt that also has the engine lift ring.

I really would rather not screw around with crankcase bolts if I didn't have to.

But I noticed a threaded location just below that lift ring, in between the two cylinders.:

The Reiff harness is laying on the top of the crankcase and is threaded through the lift ring.

What is that threaded location for? There's one on both sides of the engine.

Also, at the right of the photo is a support for the forward part of the baffling. Looks like aluminium. The Reiff harness connectors are in front of it. Is that conductive enough to serve as an engine ground?


Thanks!

That boss is used to mount the bottom leg of a injected spider bracket. It seems to that it can be n mounted on either side.

IMO - that boss would be just fine for the Reiff ground. If you have a GFIC receptacle for the heater, it will ground the airframe and protect you from shock hazard.

I just installed that system my IO360 M1B.

Bob won't accept/approve a harness modification, but I cut a wire shorter and reinstalled the connector pins. It uses mate-n-lock pins.

[Ironflight]

I agree that it is no problem to use those bosses for grounding, but I'll also say that removing spine bolts (one at a time) is a piece of cake - no problem at all. I asked at Lycoming engine school how many you could have out at one time, and the instructor sort of shrugged and said "a couple can't hurt". Just re-torque when you're done. We pull them all the time (one at a time) during construction of baffles.