I have my basic firewall penetrations sorted out, minus the routing for cables. I'm hesitant to blindly drill holes based on the plans, given I'm using a Titan IO-340 and don't know for sure that the standard locations will work (throttle, mixture, alternate air, oil cooler shutter). Would it be an awful chore to temporarily mount the engine so I can do some routing, then remove the mount with the engine still on to make it easier to finish up the firewall work? It doesn't seem like it would be all that hard to do, but I've been wrong about "easy" stuff like this before! Or am I worrying about nothing and the standard penetration locations will work fine for this engine?
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Removing Engine/Mount - 9A
- Thread starter skelrad
- Start date
It would certainly be worth checking the cable locations with the engine mounted, even if it was the standard engine, before drilling the holes in the firewall. I hung the Lycoming engine after installing the battery box, solenoids, gascolator and cabin heat box in the standard plan locations. I had marked the locations of the throttle and mixture and alternate air and needed to revise the location of the latter after the engine was hung. There was no need to remove the engine in order to drill the holes and fit the cable pass throughs, though access was a bit awkward and needed to use an angle drill.
AZSteve053
Well Known Member
You're thinking out-of-the-box in a very commendable way - on my 7 (tail dragger) build - I removed the engine & prop & mount w/ MLG legs as an assembly 4 or 5 times as I remember it - since you plan to do it... don't permanently connect wiring, fuel lines etc. from firewall & penetrations to engine. Excellent way to fit things, drill access & rivet on firewall having full access, work on back of engine when needed. Be sure to consider supporting the fuselage (and mind the balance of everything), wings if they are on are an additional challenge for supports but not insurmountable, use shot bags to balance the mount/engine/prop to keep a hands-off attitude so you can do SOLO. After 1st time - I think it took me 30 minutes to separate & another 30 to reattach. Also be sure your cherry picker does not bleed down, install a lock collar on ram of jack in case you get side tracked and have to leave it over night. Do not take firewall penetration locations off drawings without double checking both sides and all associated considerations... otherwise you'll end up with a rework or workaround situation which could have been avoided.
Attachments
It’s not hard to hang the motor on the hoist and push it in close to the firewall to plan penetrations, component locations, etc. - you don’t have to bolt it to the motor mount. It’s also only a half hour job for many to bolt it on - your choice. Like anything in airplane building, you must always assume that nothing you install is “final”…even after the airplane is flying! 
With less room to work with on my RV-3B, I made a dummy firewall from clear plastic (acrylic cracks easily, use polycarbonate or something) to determine where things should go.
Dave
Dave
Wow, the 3 has a short engine mount!
