M20J Replacing Engine Mounts

[Flymac]

We have a 78 J we are planning to replace the 4 engine mounts during annual right now, with engine staying in.  Searched several threads discussing on the sag, deciding to change out or not, etc but not about getting the mounts in/our themselves.  The lower mounts a bit unsure how we would possibly get out-especially the lower right which is right up against the sheet metal-see picture.  It actually looks like someone in the past cut that entire corner out to get to it!  Is this what you have to do?  Or do the bolts not need to back-out as you loosen them, where you can pull the mount forward instead? Appreciate any input, Thanks

[KSMooniac]

You have to remove the engine mount from the firewall. Not that hard. Disconnect the hoses, p leads, etc first do you can pull the engine forward.

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[Guest]

22 hours ago, Flymac said:

We have a 78 J we are planning to replace the 4 engine mounts during annual right now, with engine staying in.  Searched several threads discussing on the sag, deciding to change out or not, etc but not about getting the mounts in/our themselves.  The lower mounts a bit unsure how we would possibly get out-especially the lower right which is right up against the sheet metal-see picture.  It actually looks like someone in the past cut that entire corner out to get to it!  Is this what you have to do?  Or do the bolts not need to back-out as you loosen them, where you can pull the mount forward instead? Appreciate any input, Thanks

What a shame. Obviously done by someone who didn't have a clue or a manual.

Clarence

[spaz]

We just did that last week and when the lower bolts are loose there was enough play in there to clear the structure. After moving the shims around to align with the cowl getting the shim holes engine mount holes and the bolt aligned was a bit 'fidgety'. The bolts would have been easier to land if they were tapered. We didn't pull the engine out but did loosen the top mount bolts and supported the engine with a hoist.

Mike

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[carusoam]

Mike, that's a post we should save in an important place...

Engine mounts are similar to landing gear biscuits.  Rubber gets old, it flows slowly and compresses.

If it were easy and low cost, change early and often!

Having somebody carve up your footwells isn't going to make anybody happy.

Best regards,

-a-

[Flymac]

Mike, great input, thanks...so in total you were just able to loosen the 4 firewall bolts(without fully removing them) and this was enough to slide in/out the new lower mounts and bolts?  Regarding the shims, we'll probably need to play with those as well, I have the Don Maxwell article saved somewhere, did you end up ordering the mooney spacers online somewhere to use? Thanks so much!

600364-001 is one-sixteenth of an inch thick and part number 600364-003 is one-eighth of an inch thick

Edited March 10, 2016 by Flymac

[spaz]

I was able to remove the lower bolts completely.  There was enough side play when the nut removed that the bolt head cleared the footwells.  The shock absorber on the firewall side slid free enabling the bolt to slant out and clear.  I ended up referencing the DMax article, but didn't order any shims.

I was 1/2 inch low at the cowl so I estimated I needed a 1/8 shim on the engine side, IAW with the DMax article. I had a shim like you do in your photo, (1/8 inch) on the bolt head side of the mount, which wasn't doing me any good, as well as on on the engine side.  So, long story longer, there was a concern about the stackup by adding another shim, so we removed the firewall side shim and relocated it to the engine side, in the spirit of the "As Required" note on the shims in the IPC.  That made the engine rise right at 1/2 an inch at the spinner. 

Side note, DMax was the shop that hung my motor initially in 2012 so I cant account for the shim shenanigans.  I'd have brought it to him if it wasn't halfway across the country.
 

I have a before and after of the spinner but none of the in process.  I will admit once you remove the lower bolts, you are all in on this one.

Mike

[carusoam]

Nice documented explanation with photos, Mike.  The MT spinner really fits well with the cowling too.

Best regards,

-a-

 

[Guest]

1 hour ago, spaz said:

I was able to remove the lower bolts completely.  There was enough side play when the nut removed that the bolt head cleared the footwells.  The shock absorber on the firewall side slid free enabling the bolt to slant out and clear.  I ended up referencing the DMax article, but didn't order any shims.

I was 1/2 inch low at the cowl so I estimated I needed a 1/8 shim on the engine side, IAW with the DMax article. I had a shim like you do in your photo, (1/8 inch) on the bolt head side of the mount, which wasn't doing me any good, as well as on on the engine side.  So, long story longer, there was a concern about the stackup by adding another shim, so we removed the firewall side shim and relocated it to the engine side, in the spirit of the "As Required" note on the shims in the IPC.  That made the engine rise right at 1/2 an inch at the spinner. 

Side note, DMax was the shop that hung my motor initially in 2012 so I cant account for the shim shenanigans.  I'd have brought it to him if it wasn't halfway across the country.
 

I have a before and after of the spinner but none of the in process.  I will admit once you remove the lower bolts, you are all in on this one.

Mike

In all of the installations I've ever seen, there is always a 1/8" thick washer user the bolt head and against the mount.  I think you'll have to reverse the one you moved.

Clarence

[spaz]

Clarence

We actually talked about that. It was clear that 600364-003 was an optional part without a quantity specified. There are no shims on the inside top mounts. In my case, if we added another shim to the lower mounts then the bolt would be too short for the minimum thread to extend past the locking bolt. The other option as was to go to a longer mount bolt but the manual didn't allow for a longer bolt which makes sense to me with the amount of room in there.

Perhaps mine is an outlier of worst case alignment and fastener stackup. It quite obviously needed a quarter inch of lift to align. I don't even think we could fit even another washer in there though. The top has plenty of room to add additional spacers so we didn't remove any and even need them to take up thread length on the fastener. Have you run across that before, and how have you solved that issue in the past?

Mike

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[Guest]

1 hour ago, spaz said:

Clarence

We actually talked about that. It was clear that 600364-003 was an optional part without a quantity specified. There are no shims on the inside top mounts. In my case, if we added another shim to the lower mounts then the bolt would be too short for the minimum thread to extend past the locking bolt. The other option as was to go to a longer mount bolt but the manual didn't allow for a longer bolt which makes sense to me with the amount of room in there.

Perhaps mine is an outlier of worst case alignment and fastener stackup. It quite obviously needed a quarter inch of lift to align. I don't even think we could fit even another washer in there though. The top has plenty of room to add additional spacers so we didn't remove any and even need them to take up thread length on the fastener. Have you run across that before, and how have you solved that issue in the past?

Mike

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Mike,

Installing a longer bolt would a normal and accepted method when having to add shims for proper engine alignment. 

Clarence

[Flymac]

I have seen this worded several different ways now, and before we're in the middle of it and have everything loose, just wanted to be crystal clear on the shim placement, now that Ive posted a picture that we can reference: Shims are items 9 below, Engine side(left most shim), firewall side(right most shim)

-Adding a shim under the bolt head, right side shim, should have 0 impact on engine angle, purely adds to stackup of how much thread you would have showing and also how much you have to compress the mounts to aid in getting proper torque.  For both the top and lower engine mounts, the right/firewall shim has no impact on engine angle.

-Top mounts: adding the left shim is going to angle the spinner/engine down only, there is no way to utilize the top mounts to raise the spinner unless you have an existing left shim in place that you can actually remove.

-Bottom mounts: Adding the left/engine side shim is your main method to raise the spinner.  Again, no impact by adding a right side/firewall shim.

Is this all correct?

As to the discussion on needing the right side shim in place at all, as Mike points out they are AR on the manual, but yes they seem to always be installed, feels like they also give some comfort to spreading out the load of the bolt head vs being directly on the top of the mount...

 

 

[Bob_Belville]

I have considerable engine sag with 2 year old Lord Mounts. I wonder if re-tightening bolts is ever the answer. I'm speculating that due to mount compression that the torque value of the nuts might be lower than when installed.  

[kevinw]

10 hours ago, spaz said:

I was able to remove the lower bolts completely.  There was enough side play when the nut removed that the bolt head cleared the footwells.  The shock absorber on the firewall side slid free enabling the bolt to slant out and clear.  I ended up referencing the DMax article, but didn't order any shims.

I was 1/2 inch low at the cowl so I estimated I needed a 1/8 shim on the engine side, IAW with the DMax article. I had a shim like you do in your photo, (1/8 inch) on the bolt head side of the mount, which wasn't doing me any good, as well as on on the engine side.  So, long story longer, there was a concern about the stackup by adding another shim, so we removed the firewall side shim and relocated it to the engine side, in the spirit of the "As Required" note on the shims in the IPC.  That made the engine rise right at 1/2 an inch at the spinner. 

Side note, DMax was the shop that hung my motor initially in 2012 so I cant account for the shim shenanigans.  I'd have brought it to him if it wasn't halfway across the country.
 

I have a before and after of the spinner but none of the in process.  I will admit once you remove the lower bolts, you are all in on this one.

Mike

That looks 100% better. My J had an engine hung in early 2013 and it's now sagging; looks about like your "before" pic. I wonder of the new rubber in the lower mounts just settle a bit. In any case, it goes into the shop for it's annual next month and I plan to have it shimmed. Hopefully mine looks as good as yours when it's done.

[OR75]

Very interesting thread on shims install

Just one thing to consider:

when installing and reinstalling the lower and upper cowls, the spinner is often well aligned with cowling

After a flight, the cowling (floating nuts mounted) seems to rise a bit making it look like the engine is sagging. Some have replaced the floating nuts with solid mount nuts.

 

[jetdriven]

That doesn't really fix it either, but riveting a smal piece of angle aluminum to the upper boot cowl flange and glassing in a fiberglass block inside the upper cowl will fix that problem forever.  And its cheap. 

Edited March 12, 2016 by jetdriven

[Flymac]

And does anyone know the proper torque values for the mounts and firewall bolts when reinstalling? Most importantly, how/where you determined them so I can learn to lookup, didnt see in the service manual called out, unless it generally follows a standard torque value  based on bolt/thread size?

[Guest]

Torques as listed in chapter 71, bolts through Lord mounts 450-500 inch pounds. Upper 1/4" mount bolt through the firewall 50-70 inch pounds, lower 1/4" bolts are not listed, so I use the shear value of 30-40 inch pounds.

Clarence 

[PTK]

On March 11, 2016 at 10:20 PM, jetdriven said:

That doesn't really fix it either, but riveting a smal piece of angle aluminum to the upper boot cowl flange and glassing in a fiberglass block inside the upper cowl will fix that problem forever.  And its cheap. 

Do you have pics of this Byron?

[NotarPilot]

Two questions on this old thread.  How often should the engine mounts be replaced? Every TBO?

Does replacing the engine help dampen some of the engine vibration?

[1964-M20E]

My opinion if the engine is off for any reason change the mounts unless they are less than a few years old.  I'm speculating 5 years or older change them.

If you are experiencing vibrations look into having your prop dynamically balanced.  Several hundred $ and it will make a world of difference.

 

 

[NotarPilot]

9 minutes ago, 1964-M20E said:

My opinion if the engine is off for any reason change the mounts unless they are less than a few years old.  I'm speculating 5 years or older change them.

If you are experiencing vibrations look into having your prop dynamically balanced.  Several hundred $ and it will make a world of difference.

 

 

I had it dynamically balanced last year. I’m wondering if replacing the mounts might further eliminate some engine vibration.  But I do have some sag too so I might look into replacing them.

[1964-M20E]

1 minute ago, NotarPilot said:

I had it dynamically balanced last year. I’m wondering if replacing the mounts might further eliminate some engine vibration.  But I do have some sag too so I might look into replacing them.

OK

 

don't forget a mud dauber nest in the spinner will mess with your prop balance.

[Piloto]

When replaced the mounts I added an extra washer on the bottom mounts to raise the engine pitch so it will not sag down after ten years. So far no prop sagging.

José 

[Rookie]

In the New Ovations and Acclaims there are advertising a new style engine mount. Has anyone out there tried to retro fit the older engine tree to accept these?  If they work so much better why not install them on the older planes?