Replies to This Discussion

Permalink Reply by Dan Dempsey on April 23, 2015 at 7:01pm

Jon, Having made my own intake myself, I'm curious about your issue.. What was the problem?   Hope you get it fixed.  Can't you just make another one?

• ▶ Reply

Permalink Reply by Jon Reddick on April 23, 2015 at 8:18pm

It's a bit of an embarassment, but for the sake of someone else who might learn from it, I'll share.  I didn't make the intake, it was made by an acquaintance who flew this engine for about 150 hours with an ma3 (not SPA) before parting out his aircraft.  I completely rebuilt the engine but planned on using the intake that he used.  

Visually, the only major difference between this one and the one WW sells was that the carb flange was not vertical but instead was at an angle.  I never measured the angle, just assumed that since it worked for the previous owner, it shouldn't be a problem. He must have put it in to keep the carb away from the nose gear.  I rationalized that taildragger owners using the vertically mounted carb would find it tilted for all of their idling/ground running and if it didn't cause them a problem, then it should be fine.  I even called Russ at D & G to confirm this line of thinking and he didn't think it would be a problem either.  (then again, I didn't tell him at what angle the carb flange was welded, because I hadn't ever measured it.  I'm sure his advice would have been dramatically different when he realized that the flange was welded at 30 degrees off of vertical.)   

As to the problem this causes: it leaks like a sieve through the main jet.  I know it should have been obvious, but We hadn't noticed it before because the air filter box was catching most of the fuel that ran out during idle, and the prop blast was blowing it away while running.  At high RPMs, the excess fuel got sucked into the engine and it ran without any problems.  It wasn't until this week that a friend and I went to try to fine tune the idle and mixture adjustment that we really had the plane idling in one place for a significant amount of time to see what was happening.  

I'm sure the climb angle ground test we were about to do would have revealed some significant problems because the MA3 wasn't intended for extended 50 degree climbs which is what the carb would have been experiencing if the plane were climbing at 20 degrees.  

Like many problems, this one was caused by assuming, and we all know what happens when one ass-umes...

I'm not a skilled enough welder to make an intake, and have tried about fifty times over the course of the last few days to get through to someone at flycorvair.  Their message machine says that they were supposed to be back in the office yesterday so i'm not sure what's up.  Either way, i'm dead in the water until I can get an intake manifold made locally or purchase one.  

• ▶ Reply

Permalink Reply by Dan Dempsey on April 23, 2015 at 9:28pm

I think you've got some options.  You could wait until WW is answering his phone again (he might be at SunNFun).  Then you'd have to wait again for him to get something to you.  You could make the parts and take it a weld shop to weld for you.   You could draw up a little 30 degree to vertical adapter, trace the top of you carb for the flange, and it take it to a weld shop to make up for you.   Just be glad you caught it now.

Dan

• ▶ Reply

Permalink Reply by Timothy D. McCall on April 24, 2015 at 4:12pm

 

Can you cut the "Y" off on each side of the down tube where it is straight for a bit, rotate the down tube 30deg, and reconnect it with rubber hose (gas tank filler neck hose)?  This might get you through the inspection. 

Tim 

• ▶ Reply

Permalink Reply by Jon Reddick on April 25, 2015 at 7:50am

Mine didn't have a straight section. Pretty much came down in a V. I found some mandrel bends yesterday at a race shop an hour away, and basically started from scratch last night. I've got it all cut now and just need to find a skilled welder...

• ▶ Reply