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Replacing conical engine mounts in-situ

Mark Albery

Mark Albery

Well Known Member
I've decided to 'bite the bullet' and replace the old hardened engine mount bushes in my RV-4 with a set of J-1552 Lord mounts in place of the old 71032 Lycoming ones.

I'm told that they are dimensionally equivalent, so no bolt length etc changes.

My plan is to support the engine, loosen all the mount bolts and then replace the bushes one at a time without removing the engine.
Has anyone tried doing it this way or anticipates any problems with my plan?
 
Mark, aren't the 71032 and equivalent for conical and the J-1552 for dynafocal mounts?

I have a conical mount O-320 and I'm planning to buy a new set of Lycoming bushings, Spruce PN 05-08074, or the "HOMEBUILDERS CONICAL LYCOMING ENGINE MOUNT BUSHINGS" Spruce PN 08-00662. Both of those are 71032 equivalent.

I will utilize an engine hoise and try to replace them with as little additional teardown as possible.
 
Doug,

AIUI the J-1552 is a higher performance, and more expensive, direct replacement for the conical rubber bushings for conical mount engines.
My engine was originally from a Tri-Pacer.
I think that the mounts should be a lot easier to replace than on a Dynafocal mount as the bolts are all parllel.
 
I just replaced these on an RV-6 and used the J-6230-1 Lord Mounts. It does require a little bit of work, but it is easier than the Dynafocal mounts.

Vic
 
Vic,

I think that those mounts are the eccentric ones that need an indexing pin to be added on to the mounting pads of the engine frame.

My understanding is that the J-1552 is very similar but concentric, so doesn't need indexing and is a drop-in replacement for the 71032.

I think Van's sell the J-6230-1 as "EA CON VIBRATION ISO".
 
I've done several sets of both conical and dynafocal mounts "in situ". Do two at a time (top or bottom) with the engine supported by a hoist at the prop. Raising or lowering will open plenty of gap to slip the mounts in and out. Just watch for control cables or hard interference against the engine mount, exhaust, etc. usually, there is enough flex/clearance to open quite a gap.

The hardest part, really, is getting the cotter pin installed in the upper left side without screwing up the pushrod tube.
 
pushrod tube

Yes, it is very easy to damage that pushrod tube if one is not careful. Turning the bolt around seems to provide a lot more clearance.

Vic
 
I've just received the j-1552 Lord mounts.

They seem to differ from the Lycoming 71032 bushes in that there is a 3/4" counterbore around the 1/2" bolt hole.

I presume that is for an internal spacer that I don't have with the Lycoming bushes.

Does anyone know if that is correct or have a source and part number for the spacer?

Also, if there is a metal spacer then I presume the torque requirement would be more than the 40-60 in-lb that the Lycoming bush uses.

Any pointers would be appreciated.
 
I've just had my questions answered by Lord's tech support.
For reference, here's what they said:

No spacer. With the engine weight supported, tighten the bolts until the rubber just starts to bulge. Fly for 20 hours and re-check.
 
bushings

Mark Albery said:
I've just had my questions answered by Lord's tech support.
For reference, here's what they said:

No spacer. With the engine weight supported, tighten the bolts until the rubber just starts to bulge. Fly for 20 hours and re-check.
Click to expand...

The date reads that you accomplished this in March 2014. I am facing this same issue with my -4 and wondered what your results were and if you would recommend me to do the same. am particularly interested in the vibration and if it has sagged in the 2 + years since you changed them out.
My engine mount is built so that the top left mount carries almost no engine weight. its purpose appears to be to prevent horizontal movement fore and aft, while the other 3 corners bear the engine weight . would it be just as good to put a new Lycoming conical mount in that corner and Lords in the other 3 ?... Thanks,.... George
 
They're holding up fine, with no noticeable deterioration. The Lord mounts did improve the vibration; not dramatically but noticeable.

They are a lot more expensive than the black rubbers, so you'll need to make your own value judgement
 
Mark is correct

The 1552 goes in easily and is concentric with no steel tube insert. It is thinner than the 6113 rubber, so be prepared for washers if you have a spinner clearance issue.
 
Thanks Larry and Mark. I have a spinner clearance issue now with the old ones so I kind of anticipated the additional washers. My bottom left cones were worn right down to bare metal so its good I caught it when I did.
Going to go with the J1552s ... The engine had sagged probably a half inch and put #1 exhaust pipe close to the cowling . Hoping these new mounts clear that issue up too..
Thank you both for your inputs... George
 
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