O-320 Crankshaft Front Plug

dclay · #1 04-29-2007, 07:17 PM

Guys,

I need some help. I?m complying with the AD for inspecting the I.D. of the crankshaft for corrosion on my O-320 and have found that the front plug I removed from the crankshaft doesn?t look the same as the new plug (lycoming p/n STD 1211) that I purchased from A/C Spruce. The plug I removed, which is probably the original that the factory installed, has about a ?? flange around the outer diameter. However, the new plug doesn?t have the flange on it. It just looks like a slightly convexed disc. The part number matches what the Lycoming Parts Manual says is supposed to be installed but I?m concerned about the new plug not looking the same as the one that was removed. Has anyone else experienced this?

Thanks,
Dave

joeboisselle · #2 04-29-2007, 08:38 PM

yeah, mines the convexed disk you have. I was going to silicone it in place unless somebody has a better idea.

az_gila · #3 04-29-2007, 10:11 PM

Quote:

Originally Posted by joeboisselle

yeah, mines the convexed disk you have. I was going to silicone it in place unless somebody has a better idea.

Maybe silicone, but Lycoming recommends a special drift tool to insert it. I believe you put it in place convex side out, and gently "whack it" with the drift to reduce the curvature and make it stay in place...

gil in Tucson

Mark Burns · #4 04-29-2007, 11:42 PM

Yep, it looks strange for where it goes.

The lycoming drift is VERY expensive.
I researched this awhile back, and just installed mine today!

Put #2 permatex around it and install it convex out (toward prop).
I used a brass bar about 1" in diameter for a drift, and smacked it with a big hammer about ten times. They say you want it sorta flat but not all the way flat. It's only got to hold crankcase pressure.

Mark

Rivethead · #5 04-29-2007, 11:51 PM

I just installed a plug in my crank. Don't silicon it. Place the plug in position take a large size ball peen hammer and place it against it. Strike the ball peen hammer with another ball peen hammer until it sets the plug in place. I finished with a piece of wood slightly smaller than the inside diameter of the crank and hit that until the plug when tapped with the hammer made a nice solid sound. If the dome of the plug presses in, as in, becomes concave the plug is ruined and should just be removed and a new one inserted.

dclay · #6 04-30-2007, 10:39 AM

I?m not sure what everyone is using for a driver on the plug, but I?ve been told that a 1-1/4? PVC coupling (schedule 80) will slip in the crankshaft I.D. and can be used to drive the plug into it?s seat. This focuses the hammering energy around the edge of the plug and prevents distorting the surface in the center of the plug.

Has anyone used this method before?

Thanks,
Dave

airguy · #7 04-30-2007, 04:55 PM

The whole point IS to distort the center of the plug. By flattening the convex bulge in the center, you are distorting the outside diameter of the plug, trying to force it ever so slightly larger, resulting in a tight bind (seal) between the outside diameter of the plug and the inside diameter of the crank. You want to distort the convex face of the plug towards FLAT, but not so much that it becomes CONCAVE - this will remove the pressure from the outside diameter of the plug and it becomes scrap.

dclay · #8 04-30-2007, 06:49 PM

Ok, the light just came on and I understand now. I was under the impression the plug was interference fit and had to be driven or pressed into its seated position. However, I must admit I?m a little apprehensive about hammering on the crankshaft and the load it imposes on the thrust ring. I know it?s supported by the bearing but it?s still an expensive part to be pounding on with a hammer.

Thanks for the info. This forum is great!!
Dave

airguy · #9 04-30-2007, 09:32 PM

Using a hammer against the plug is not actually going to put that much stress on the bearings, unless you're swinging an 8-lb sledge. Use a ball-peen hammer, and physics will be on your side. The inertia of the crankshaft will work against the inertia of the hammer, and the metal between the two (shaft plug) will be doing the deforming. The mass of the crankshaft is large enough to absorb a great deal of energy from the hammer without transferring it to the thrust bearings.

N941WR · #10 05-01-2007, 07:48 PM

I just used a chunk of oak I had laying around that fit down the shaft then wacked it with a hammer.

HOWEVER...

Before putting the plug in I punched a hole in the aft plug to let oil back into the engine. If you don't do this, oil pressure can build up and push the front plug out.