Engine Mount Clearance Mod

Updated 10/30/05
Here is the IO-540 Engine Mount Clearance Modification photo set sent to me by Scott Risan at Van's.
They have been very very good at dealing with this issue for me.  I think that hearing it from a few people now, they determined that there may be a potential issue for some customers and they wanted to figure it out a.s.a.p. and come up with a correction or a plan.  I sent them my engine mount via FedEx and they got it the same week.  They actually analyzed it right away the first day they got it in, and dropped me a note.  Then, on Friday (the next day), they actually had someone come in to perform the welding so they could ship it out that same day.  (This is extra special, since the guys who do this work 4 tens, and don't usually work Friday).  They also offered to powder coat the weld if I wanted to wait a week or so for powder coating, but I opted to get the mount back a.s.a.p. so they were going to try to ship it back Friday.  Great service....turn around in one day.

Here are some facts:
When they placed the engine mount in their test case, they had 3/16" to almost 1/4" clearance.  That's still not 1/2", but it's about double what I had (.063 to .125")   They feel there must be a difference in the sumps.   I gave them my sump numbers because they want to investigate what the difference is.  My numbers were:
and a number that looks like Z1902

They say they aren't seeing any problem with the brand new Lycoming engines they're selling. Their first-glance look seems to indicate that my sump may be an off number from what they are used to seeing. Remember that any engine you buy, Aerosport, or any other non-factory-new, will be a rebuild that will potentially be built out of cases and sumps from any model year or number. This could cause some of these small variations. There is no such thing as an "Aerosport IO-540" as one list member wrote. They are all just rebuilds of other IO-540's that aren't factory new....and can be of various previous lineages.

It is also interesting to note that according to Van's, the cross bar in question was determined unnecessary by engineering, but someone working with the engine mounts decided to add it anyway to add more structure and support. Given the solid design, I'd believe this, but when you see the mount, I think it's still best to have the bar there. That said, I can't picture there being hardly any stress on this particular joint. I could picture the "fix" being done without welding....cutting the tube, and bolting in a curved piece. Of course, a bolted joint would give more opportunity for corrosion where the tubes meet, so I'm happy with the welding option.

So my modded engine mount is now enroute back to me, and I should be able to hang the engine for next weekend. It was a bit of a pain, but at least it didn't cause a major slowdown. My advice? Get your engine and mount hung while you're working on the canopy and fuselage. Then you can tell if you have any issues, and can pull it immediately and send it out for rework without slowing anything down. I am under the impression that Van's might be willing to work with future builders on this problem. I am not sure if they plan to make this mod part of their general contstruction in the future. If anyone gets that answer, let me know. They have been very good dealing with this for me though. Thanks Scott! (and Bruce)


Update after Engine Mount Returned

As you can see by the photos below, the engine mount came back sucessfully, and it now has more clearance than it used to.  I don't think I have anywhere near 1/2" on the outside edges, but probably at least 1/4" everwhere, and more in the center.  I would sure think this is enough, except I recently heard that the throttle/mixture cables were actually supposed to go between the engine sump and that bar....that I just don't think would be a good idea, given the current state of that gap.  One other thing I'd do slightly different....The new bar curve is about 6" in length.  The sump is also about 6" wide.  If they would have made that curved piece about 7" wide instead, there would be more clearance on the outer corners of the sump.

For those who might be interested in this tidbit:  I repainted that bar of the mount, because I didn't want to wait for Van's to send it out for powdercoating.  I mixed up a batch of K36 Primer/Sealer, which uses 4 parts K36, to 2 parts Concept Paint, plus DCX61 Hardner and reducer.  This stuff almost perfectly matches the powdercoat color, so it's amost unnoticeable and you'd never know it was different unless you were looking really closely...in person.  I don't think you'll see any difference in the photos.

All in all, I think Van's did a good job on taking care of this for me.  Thanks to Scott Risan, and Bruce Reynolds, who were great to deal with on this issue.   I suggest to other builders that if you have a problem with a part, definitely send them a photo, and call them by phone to follow up.  I think you'll get a better response if you take the time to illustrate your issue for better understanding.  Same goes when posting to the RV-10 List....a picture is worth, well, you know... :)


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