Stjohn's RV-7

4 hours.

I’m convinced an optimist is a pessimist who hasn’t done a firewall-forward installation yet. Let me amend that. With a plug-and-play setup, that optimism might keep going, but with a frankenmotor like mine, the odds are definitely stacked in a bad way. I decided to tackle one thing at a time. First thing is the throttle body arms. I rotated the throttle body so the diaphragm points to 3:00 again, if you’re looking over the nose. I came up with a scenario that should work, but it might require the use of heat shielding on the control cable end, not sure if that’s a no-no or if it’s OK. Take a gander:

Here, we’re looking up at the engine. First thing to check out is the throttle arm. I ground off the outermost hole so it can swing past the exhaust pipe with enough clearance to make me sleep well at night, but it’s still tight in there. The second thing is the mixture arm. If I’m reading it correctly, it’s in the full rich position right now. Push for rich, pull for lean. I have a call into AFP to see if this will work, but I suspect it will. The bracket bolted to the sump is one of the Van’s IO360 brackets. It’s almost perfect, except for the fact that the bolt holes don’t line up for the Superior sump. Another 1/8 of an inch apart from each other and they would.

Close up. Do you see how tight it is in there? This is like a game of Tetris, but none of the pieces are the same shape.

From the left side. If I rotate the TB so the diaphragm is at 12:00, it bangs into that black rod on the starter. No joy there. Plus, it would make cabling suck even worse, and there would be bellcranks and other fun stuff.

This shot shows the potential path for the mixture cable. A small spacer putting the rod end bearing slightly above the mixture arm should get it easily clear of the other arm and bearing.

This is the throttle cable lineup. Since I could clock the throttle arm in any direction I wanted, I got it so the arc is the best compromise for non-interference with the mixture arm, but also I need certainty that there won’t be an over-center condition on the arc swing. there’s still plenty of room to bend the bracket upward, which sends the cable out well clear of the exhaust pipe. I’m trying to keep the rod bearing on top of the arm rather than below it, because I want as little radiated heat as possible soaking the cable. I now need to mock up brackets to make this work.

Oh, and I discovered something disturbing today: a couple of rotation locks that I believe go inside the fuel tanks to stop the fuel pickup tube fittings from backing out. I’m pretty sure though, that those were the old kind, and the new kind are what’s installed in the tanks. I may have to run a scope in there and check it out, but if there’s no rotation lock on there at all, taking that apart to redo it is going to blow, long and hard.

I read all the warnings. “Use a Van’s-approved engine or you’ll have a ton of trouble making everything fit.” Or this one: “By the time you convert the engine to what you want, you’ll have spent just as much money as if you’d bought new.” Tinker or fly? So, I now have a laundry list of issues related to my particular setup that will now require no small amount of customization, some of it in steel, which I haven’t had much to do with since shoehorning large snowmobile engines onto the backs of go-karts back in the mid-80’s. Here’s the list of fun so far:

-Throttle body interferes with the starter. The Kelley Aerospace starter has a retaining bolt on it that prevents the TB from being mounted in the diaphragm-up position.
-Stock brackets won’t work. Either the mixture or the throttle arm goes the wrong way when pushed, so a bellcrank is probably going to be required.
-AFP throttle body won’t play nice with the airbox. More fun with fiberglass.
-Fuel hose from engine pump to TB inlet is too short in any position except the one that won’t work because of the starter.
-Custom-length quadrant cables will be required.
-Throttle and mixture arms interfere with factory-set linkages when oriented in directions that work for me. I’ll need a straight arm from Don at Airflow.
-Right magneto interferes with battery box. Will need to be re-indexed for harness to clear and be retimed.
-Left magneto had to be removed to adjust oil cooler fitting. Timing will need to be reset.
-Breather tube is a little close to the RDAC. Should be OK though.
-Alternator interference unknown at this time, since I haven’t purchased it yet.
-Oil cooler taken off the engine when I got it is cracked. Need a new one.
-Oil pressure fitting is AN3, not AN4, so the supplied hose won’t work. Earl’s doesn’t seem to have a steel expander either.

So should I have listened to the warnings? Waited for a a good deal on an engine with a standard Bendix fuel injection system that wouldnt’ have necessitated an aftermarket, oddball sump? Maybe. Am I kicking myself for not doing so? A little. Thanks to the teardown/rebuild, I’m pretty much out of money and it’s going to take some time to build up reserves. I could probably still fit the cowl, and I can definitely get the avionics and wiring done, but the firewall-forward engineering may be my greatest challenge yet. But I know a guy at Crashspace with a 6-axis mill and a lathe. Van’s Air Force is still my lifeline. And I’m in too deep to quit now.

As I write this, I’m on Alaska Airlines on initial descent into LAX, returning from Vancouver, BC. If human beings can figure out a way to get me online in a big spam can at FL30, I can find a solution to the nearly-overconstrained problem of the firewall forward situation.