SonexBuilders.net

Could the problem be carb ice? Those carbs originally had carb heat available.

I don't think so. It happened at a high cruise power setting, without any reduction in throttle. Also, I don't think carb ice would cause the increase in fuel flow above max engine consumption. This pretty well points to refilling the float bowl and/or fuel lines.

I had the same thing happen with the same carb in my Pietnpol. It ended up being a partial restriction in the carb. A piece of something made it into the bowl and partially blocked the pickup in the bowl. It happened first on my dowwind leg at Brodhead, then again on base - then nosed over during taxi after landing. I goosed the throttle, no help, punched the choke - and it backfired and blew my exhaust seat loose in the A75.
Lorin
N81YX - 250+ hrs and having fun!

hi all,
One more item to consider, after re-reading all the posts in this thread, is what type of fuel are you using? Auto? , 100LL?, or a combo of those two? If its just auto fuel, id go back to the vapor lock scenario.

WaiexN143NM
Michael

any update?

I've only flown it on two quick flights since my first post. I've been rather busy with work. I didn't like how my fuel vent seemed to be disrupted by the cowl exit. I thought maybe under the right conditions, a low pressure area was developing. I have moved the fuel vent away from the cowl exit and now face it directly in to the wind. Like I said, no issues thus far, but I should be able to fly it a lot in the coming week. I am using 100LL for whoever had asked.

Did this issue get resolved? Or still too early to know...

Eagerly awaiting your findings...

Gordon

Hi Gordon, I've put another 1.5 hours since moving the fuel vent. Still no sign of any issues. I'm hoping it was just the fuel vent in disrupted air from the cowl exit. I'm using a MA3-SPA and I don't think we get the recommended head pressure with our Sonex tanks and the short downhill run. Any disruption to the marginal head pressure we get might be enough to cause the problem I was seeing.

I am going with the same set up, 3.0 corvair and ma3 carb. Would you mind describing your Fuel Flow installation?

I'll see if I can find some pictures when I get a chance. My fuel system is as follows;

Finger Strainer
Fuel Valve
6AN braided line to firewall passthrough
Summit Fuel Filter
6AN braided to Red Cube
6AN braided to carb