Dave’s RV-7A Building Log

Firewall forward advice

In response to a question about firewall holes for an IO-360-M1B in an RV-7/7A with Precision Airmotive fuel injection, Pete James sent me an email with some great information and pictures. I’m copying it here (with his permission) so that others can benefit…

Dave,
I too have fitted an IO-360 M1B with Forward facing Fuel Injection, albeit from Aero Sport Power. I followed Vans FWF plans and the holes in the Fire Wall all worked, though I had my doubts at times. But there are a few things NOT mentioned in the plans!

You don’t need the Fuel Doubler for Fuel Injection. It is for the Carby Gascolator. Vans doesn’t recommend a gascolator for the Fuel Injection. (DP - This is the Facet fuel pump doubler called out on the firewall plans. It’s not needed for fuel injected engines.)

The only major problem I had was that when I had finished the baffles the Snorkel Air box did NOT fit, as it is designed for the Angle valve engine which is an inch or so wider at the rocker covers (where the side baffles attach) and so the Airbox protruded beyond the side baffle.

I had to un-rivet the baffles and move them out board. There is no warning of this, so when it comes to the LEFT HAND FRONT BAFFLES make them to fit the AIRBOX, NOT the Intake cowl lip as described in the Baffle Kit.

Throttle, Mixture and Prop cables went well; with slight mods. There are no drawings for these, only B & W pics so I have attached some decent pics of mine.

1. I made a new bracket (from two pieces) for the throttle cable where it attaches to the bottom of the sump to lift it further from the exhaust.

2. Mixture went on as supplied. But it has a complicated bell crank.

3. Pitch cable went on as supplied, although the angle of exit at the front of the firewall looked excessive. But the pitch lever moves freely.

4. I initially used the Steel Eyeballs from Vans for the Fire wall penetration; because I thought they would be more fire resistant than the Aluminium ones. They are held with six tiny screws and cannot be drilled out to the Control Cable size with out destroying them. I then ordered the One Piece Aluminum (Blue) ones as shown in attached pics. They are excellent.

5. I fitted a Park Brake valve. I once parked my mates RV-8 on smooth tarmac in a 30KT wind and could not get out as it started blowing away when I released the toe brakes. I fitted the Park Brake Valve on the cockpit side of the firewall, where the lines penetrate the fire wall. The holes in the park brake block are different to those on the plans. If you plan to do this, let me know and I will send more details.

6. In case you don’t know, when drilling Stainless (Firewall) if the drill or hole saw stops cutting then the stainless will work harden VERY quickly and you will not be able to complete the hole. Keep pressure on the drill.

7. I had to drill holes after the engine went in for things like my Ground Power relay (for jump starts). It is very difficult to get a drill in behind the engine once it is in. If you look at the picture of the GND Power relay you will see that I had to position it where I could get the drill around the engine mount. VANS DOES NOT INCLUDE CONSIDERATION FOR WIRING HOLES. You need to plan for this. Accept for my Gnd Power wire, all my avionics penetrations are at the top of the firewall, where they are easy to drill.

8. I used Clocs on the Cowl to firewall, not Piano Hinge, so that I could quickly remove the cowls for daily inspections. By the time I finished the cowls and baffles they had paid for themselves, as I must have had the cowls on and off 50 times. Check http://www.skybolt.com/
WHETHER YOU PLAN TO USE CLOCS OR PIANO HINGES YOU SHOULD FIT THEM BEFORE YOU FIT THE ENGINE FRAME OR IT IS NEARLY IMPOSSIBLE TO COMPLETE THE FIREWALL RIVETING.

9. I used Carbinge Carbon Piano hinges on the cowl to cowl joins as they come with a superb keeper with an Allen screw that screws in flush and retains the hinge pin. Check http://www.carbinge.com/