Firewall penetrations for 7A with Lyc IO360 M1B

[david.perl]

Hi

Im about to drill the holes for the firewall penetrations for throttle, mixture and prop controls. Is the locations shown in the plans accurate as I don't yet have an engine to see if the positioning is correct? I ordered the standard cables in the Vans FF kit for the injected IO360 with CS prop.

Also where does the hole go for the cable for the alternate air supply?

thanks as ever in advance

David

[mburch]

Hi David,

If you search for "eyeball" on my website (link below) you can see where I put mine. I seem to recall that I used the factory specified locations for throttle and mixture, and moved the prop cable slightly. I will go out to the garage and measure for you as soon as it warms up a bit.

- Matt

[david.perl]

Matt - that's really appreciated - thanks David

[shuttle]

Hi David,

Mine is a 7, not a 7A, so I won't comment on throttle/mixture/prop save to say that the plans position worked just fine.

Re: Alternate Air Cable Passthru, mine is on a pretty much straight run from the cable control knob under the left air vent (bottom left of panel) to the snorkel Alt Air Door. The cable runs along the bottom of the cylinders. When I made the engine baffles I extended down a little the angle at the corner holding the oil cooler to provide support for the cable (an idea I copied from another VAF poster).

Have included a couple of photos below.

Note:
1) In the 2nd photo the cable is not going though the passthru, hence the upward path of the cable near the FW.
2) I have since swapped the passthrus for the steel riveted eyeball type.
3) I installed the Alt Air Door on a 1.5 inch cylindrical blister (not shown) on the side of the snorkel to keep the cable run straight.





Regards,
Steve

[mburch]

Okay, here are my FW eyeball positions, measured as best I'm able on a mostly-finished firewall (which is not terribly precise). Should hopefully be near enough to let you compare them to the plans positions. All locations refer to the center of the hole. Also note that my airplane is a taildragger so the geometry of our respective engine mounts will be different.

Throttle is about 5 1/4" up from the bottom skin, and about 3 1/4" inboard from the rivets that attach the F-601N-R vertical stiffener. My notes say I moved it 1/4" up and 1/4" inboard from the plans location in order to clear the existing doubler for the carbureted fuel pump.



Beware of conflicts with the fuel hose, and also note that the plans location for the fuel hose should really be another 1/4" inboard to give more clearance for the starter solenoid. Additionally, I later had a tricky situation with the throttle cable versus the exhaust pipe hangers where the available clearance would have been a little better if I had moved the throttle cable hole straight up instead of up-and-in:



I recall having issues with the throttle cable, in that it is tricky to get it all the way from the back of the engine to the front without touching the exhaust pipes or fouling on the corner of the oil sump, all while ensuring sufficient travel from stop to stop. Even when it's all correct the clearances are none too generous.



Mixture is about 4 1/2" down from the rivets that attach the F-601L angle that goes across the top of the firewall, and about 11 1/2" in from the fuselage side skin (port side). No real issues with the firewall location of the mixture cable (routing it around to the front of the engine is a different story).



Prop is at the same elevation as the mixture cable, and about 8 1/4" in from the fuselage side skin (port side). On this I would recommend choosing a lateral position that gets the prop cable as far outboard as possible while still remaining inboard of the diagonal fuselage stiffener (F-601D-L). Or to put it another way, tuck it right up against the inboard of the diagonal stiffener, remembering to provide clearance for the eyeball screws. I believe the "no!" hole location in the photo below is the plans position, which I think would be tricky to make work without hitting the left magneto.



Alternate Air cable is in pretty much the same location used by Steve in the post above. This ends up being pretty precisely located in order to clear the engine mount, so I would recommend waiting till the mount is fitted to drill this one. For reference, mine is about 2 1/4" in from the fuselage side skin, and 6 1/4" down from the upper-left engine mount bolt.



Hope that helps.

good luck,
- Matt

[david.perl]

Matt, once again thxs. Thats really helpful.

[Rupester]

For my 9A with IO-320 vertical induction, the throttle pass-thru location shown on the plans was fine. The mixture location wasn't even close - wouldn't work even with the longest mixture cable Vans offers. (I ended up using the Vans mixture opening in the F'wall for the alt air cable.) The final mixture pass-thru is on the slanted upper surface of the firewall indent.
I realize this is not as helpful as the photos in other posts, but I did a lot muttering and cussing trying to "figger out" the firewall penetration. Hopefully, you won't.