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Avcon/ Williams STC motor mount isolator alternatives.
Posted: Fri May 02, 2025 8:41 pm
by abushey123
Hello every one. For those looking for a less expensive alternative to the J-3804-28 mount, the following part numbers can be used. All Lord mounts use a jelly spacer with the squish tube which helps with dampening on startup. This is not necessary if using a carbon propeller. aka Newton’s third law makes the prop spin faster rather than the plane feeling the torque of engine start.
J-3804-28 1200 lb/in shear springrate ——- stock option.
J-3804-31 1400 lb/in
J-3804-37 1650 lb/in
J-3804-39 1750 lb/in
J-6545-1 1200lb/in This using a different type of isolator.
Barry mount options:
94110-40. Same as J-6545-1
94110-02 same as J-3804-28 minus the jelly spacer.
Cheers and happy shopping!!
Re: Avcon/ Williams STC motor mount isolator alternatives.
Posted: Sat May 03, 2025 9:18 pm
by DaveF
Good info.
More here:
viewtopic.php?p=139316
Re: Avcon/ Williams STC motor mount isolator alternatives.
Posted: Wed May 07, 2025 4:01 am
by EMB505
I wish I had this info a couple of months ago. Those Lord mounts are now $500 a piece! I just installed them today.
Re: Avcon/ Williams STC motor mount isolator alternatives.
Posted: Tue Jun 03, 2025 4:23 pm
by redacted
typo fixed
My contents list for my Avcon conversion shows the mounts as J7402-5
Anyone shed any light on this? Thanks
Re: Avcon/ Williams STC motor mount isolator alternatives.
Posted: Tue Jun 03, 2025 8:03 pm
by DaveF
You mean J7402-5?
It would be nice to know the differences between these!
Re: Avcon/ Williams STC motor mount isolator alternatives.
Posted: Tue Jun 03, 2025 9:02 pm
by redacted
Yes, sorry for the typo. 7402-5 Bill of materials dated 1977
Re: Avcon/ Williams STC motor mount isolator alternatives.
Posted: Wed Jun 04, 2025 11:37 pm
by DaveF
Can you post a picture of that page? My 1973 Avcon paperwork shows the J-3804-28. It would be nice to have another option.
Re: Avcon/ Williams STC motor mount isolator alternatives.
Posted: Thu Jun 05, 2025 12:00 am
by redacted
PDF attached. Bottom of page 2.
Re: Avcon/ Williams STC motor mount isolator alternatives.
Posted: Thu Jun 05, 2025 1:30 am
by DaveF
Thanks. You must have Bush conversion STC SA421CE. It's basically the same as Avcon SA806CE, but is not identical. Engine mounts are different.
Re: Avcon/ Williams STC motor mount isolator alternatives.
Posted: Thu Jun 05, 2025 5:11 pm
by redacted
Actually I do have the Avcon STC and not the Bush. This PDF....not sure if I found it on here or online somewhere or in a thumb drive for the plane. But hey, it's another engine mount option as you head down the rabbit hole.