Chapter 23 – Engine & Cowling Plan

First off, I’ll let ya’ll know that I’ve had a cold for the last couple of days so I’ve been taking it easy as I assess my engine vs. cowling position issue.

Yes, over the last few days I’ve had a bit of an epiphany on my engine and I thought I would share it with you.

I have to face this issue down, and seriously determine and fix why I’m having any interference or just really tight clearances on my cold air induction pipe, my fuel injection servo, my exhaust pipes. my RAM air can, my mechanical fuel pump drain with my aileron control tubes, and now my prop spinner.

My initial assessment, again, is simple: something just ain’t right in Denmark…. the engine looks like it’s sitting in there fine, but all the indicators tell another story.

Ok, my troubleshooting skills may be slipping I guess.  But I think I’ve got at least two contributing factors.  My bad for not thinking this out better:

Here goes:  Mike Melvill had an O-235 and rigged his engine to be level at 2° nose high per plans… Or about 2° engine high at level longerons.

He then swapped his O-235 out O-360, same mounts pretty much.  Cowling goes on the new engine which is still set at 2° high.

With a planned more powerful motor, I went with 1.4°… but am measuring even less.than that.  Probably not surprising since it’s been on the engine mount for 4 years now.

Now, my bird isn’t on a level floor, nor did I level it, so probably some slight variance.  But I’m measuring 1° on left, 1.2° on right as far as prop up in the back.  That equates to 0.2″ low on left and 0.16″ long on right if I were to bring it back up to 2°.  Significant when you’ve got close to zero clearance on the left exhaust pipes, and a lot of tight clearance issues with a myriad of other stuff.

When I was talking with Marco I wasn’t sure what angle I had set my motor at, but on my blog I noted that I set mine for 1.4º.  I used a .224″ spacer to get to 0.0º on the engine mount, while plans requires a 0.25″ spacer to get to 0º.

Looking at my buddy Dave Berenholtz’s blog, I noted he had a seemingly much tougher time getting the bottom cowl on than I did.  The major difference in our installs is that Dave had an O-320 motor installed on the plane to confirm that the bottom cowl needed to be angled back, or down on the back end.

In addition, Dave’s front top corners are about where mine are, which means the bottom of his cowl where it meets the bottom of the fuselage/firewall is most likely trimmed a good bit more than mine, angling his bottom cowl down on the aft end.  I would think that mounting the bottom cowl as he did caused issues on getting the sides lined up because the back end was actually where it needed to be.

I didn’t have the issues along the sides because I didn’t have my motor installed (huge error) and all seemed peachy keen installing it upside down.  Since, as I pointed out in my video, I only trimmed a max of 3/16″ off each side, most of it way less than that since it was a slight angle, I grossly underestimated how jacked up the cowling was in its design as far as NOT being anywhere close to plug ‘n play.

1.  With my engine angled slightly down in the back more so than stock plans,
2.  Not confirming engine to bottom cowl fit with the engine in while installing lower cowling
3.  Resulting in engine sitting slightly low (some of that may be from 4 years on mounts) and cowling significantly higher compared to stock

I need to take some significant steps to mitigate my engine configuration issue.

#1 – I’ve been researching shims on engine mounts.  Apparently not that uncommon.  A number of reports of engines that start to sag or droop, and shims are used to get them back up to previous level.  I spoke with the Lord mounts folks and, with caveats and warnings to replace old mounts, I’m leaning seriously towards not replacing my mounts and shimming the bottom mounts to bring the engine back up to 2º.
#2 – After I shim the motor up, I’ll then assess its position.  I then need to be prepared for some possible major rework on the lower cowl to re-skin the aft area to open it up for exhaust pipes and spinner/flow guide.
#3 – I will work what I can on the exhaust pipes to possibly have them angled up just a scooch to add even more clearance.

I expect all this to add about a month to the build completion date.

Yep, mods can bite hard sometimes eh?

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