This is getting frustrating...LA46 in ARC Cardinal. Uniflow clunk with uniflow terminated halfway down outboard wall. 2 head shims and small FP40 venturi, ST needle, power master10/22 fuel, XOAR 12-4 or APC 12.25 x 3.75.
Here's the issue...going rich inverted. I know to adjust the uniflow tube up or down but this one is acting very strangely. I keep adjusting it the correct way and it deos get better but the end of the tube is now WAY below the spraybar when inverted. I know I'm moving it the right way...i know how it works but I have never had to adjust one this far below and still can't get the lap tiems the same. What am I missing?

I have had the tank leak but it always caused it to jump lean at take off and stay there for a very fast pattern! It was the screw in fron t of the cap. I could tighten it and it would go back to normal. Now that i think aobut it this alll went awry when I went form 5 to 10 per cent nitro. I didn't change anything but the nitro amount. Maybe need more compression now? Like take out a head gasket? I actually took the plastic tank off yesterday and put a brodak 'all tubes forward' uniflow on there but have not had time to try ity yet. What's frustrating me is this engine ran perfectly for aobut 3 months of flying...just got to practice the pattern over and over and go through gallons of fuel. Now every time I go fly it's trying to get the motor run back...

Will do...it's always the simple stuff that gets us huh?

Will do...it's always the simple stuff that gets us huh?

At least we should always check the simple stuff first.  I often remember this rule after I'm up to my elbows in disassembled equipment and I find out that the power cord is unplugged, or the fuel tank is empty, or something like that.

Yeah...tightening that stopper screw is a regular maintenace I do but sooner or later you can hear it go "click" and you have to fish out the little curly q of plastic from the back washer stripping out. I'm trying a metal tank now. I know some have great luck with them but I have just had nothing but hassles with plastic tanks...and I have tried siamese,,,uniflow halfway...to the front...to the back... every which way there is I think. I put a uniflow metal on it and am waiting to go try. The ONLY reason i had a plastic tank on the plane was because I THOUGHT the LA 46 was using more than 5...close to 6 ounces but after cutting my after pattern laps to 3 or 4 and running it a little leaner I can do the pattern and 4 laps on exactly 4 ozs....so i put a Brodak 4 oz uni on it.

OK folks...I yanked the plastic clunk off and installed a Brodak 4.5 oz ATF wedge. So i start adjusting the tank to get upright and inv laps the same and I'm in the same ballpark as the clunk tnak. The uniflow is a good 1/2" below the needle inverted and still slower than upright. Is this normal?.....for the tank to be SO off center. I cant raise it much more...it will be off the damn fusealage. Never had this problem before. I mean I have had to raise or lower a little but this seems extreme to me.

What's frustrating me is this engine ran perfectly for aobut 3 months of flying...just got to practice the pattern over and over and go through gallons of fuel. Now every time I go fly it's trying to get the motor run back...

Just wondering was the temperature cooler 3 month ago where you are?   if so maybe put back 1 head shim (see below) might help.

* Correction: I meant remove 1, not put back.

If you have the tank 1/2" below engine centerline and it's going rich inverted, you need to raise the tank. When the plane is inverted, the tank is then above centerline, so naturally, it delivers more fuel.  Steve

The tank is 1/2" above centerline upright...so it is way below centerline inverted and still running rich inverted.