I believe i am having fule draw issues but need some advice.
Set up: LA 46 stock with kustom kraft needle (.156) and 285 venturi, metal backplate, thunderbolt RC long plug, 2 exra head shims, powermaster 5/22, metal 4.5 oz uniflow with pressure, tongue muffler (don't know from whence it came other than out of my bag from the 90s...suspect i bought it for an FP40 back then) prop right now is power point 11-4. tried APCs and Xoars but the motor seemed to get bogged down and use lots of fuel.
So here is the issue...it burps or dies in the overheads or clover and still has plenty of fuel. If it makes it out of the clover it goes 10 more laps or so. Launching at 11,400 and it will go into a wet 2 strong 4 but if I get it just the slightest lean it goes screaming and detonating...I can hear it but also feel it in the lines!!! Cooks oil all over the head and stuff.
 So my question is do I have the head decompressed too much...too big venturi? Does it sound like fuel draw is the culprit? I have a 260 venturi or whatever the small one was with FP40s...a 17/64 drill bit goes through with very slight resistance. Would that increase fuel draw and stop the burp?

   This is almost certainly a function of the tank, not the engine. Tilt the tank in plan view so that the rear of the tank is kicked out maybe 1/8-1/4", and see if that fixes it. You might have to increase the wedge angle of the tank to get this right.

    Any question about the engine setup can probably be answered by putting it back to the original stock parts, then diagnosing any issues from there. An 11-4 APC *should not* bog down a 46LA -if it does, my first suspicion is that you should take out the head shims and put it to the stock configuration.

     But, the problem with the cutoffs is a tank issue.

  Brett

Chris complains about engine cut-out in overheads.  This is near the end of the pattern, but still more to go.  Therefore, he is not out of fuel.  I almost always use rectangular tanks, and not necessarily "canted" outward.  It seems that with some fuel remaining, centrifugal force would keep fuel at the pickup tube, unless lap times are so slow that fuel is "falling"?

   The maneuvering is driving the fuel towards the "bottom" of the tank. Directly overhead, you only have about 1.5gs pushing the fuel up against the wedge, and maybe 3-4G's worth of maneuvering load, so the steady-state fuel surface is close to parallel to the bottom, pulling it away from the pickup. Changing the wedge angle helps by slowing down the rate at which the fuel moves away, and canting the tank makes the depth greater near the pickup.

    The Veco T21 style wedge is very near the critical wedge angle. It was probably mostly OK back in the day with relatively gentle maneuvering, but it's not quite steep enough for the much more crisp transitions from straight to curved that are necessary to compete today. For me, it needs to be just a bit more acute than the Veco, and there aren't a lot of people flying their 4-leaf tighter than I am.

    Once the maneuvering stops, the fuel goes mostly back to the outside, and the fuel surface angle goes back to the usual ~70 degrees (nearly perpendicular to the bottom of the tank).

   This is an extremely common issue. What is needed is a tank that will run as close as possible to exactly the same even through the 4-leaf, with almost no fuel remaining. Then cut off immediately without surging back and forth (due to fore-aft fuel slosh). Of course this is necessary to run the fuel as close as possible to give you more margin between completing the maneuvers

      Brett

Chris,
I agree with Brett,, however one other thing I experienced with the LA having exactly the same symptoms on my profile Gee bee... I found that I was flying with the airframe yawed out ,, moved the leadouts forward ( which is where they should have been any way,, I was a trimming rookie,, what can I say) this put the airframe closer to tangent and my problem went away,,
I did have my tank canted out on the aft end prior to, and after this,,

so its another thing to look at,, but ultimatly what fixed it was getting the tank to feed properly when overhead,,,which is what Brett said,,

that said,, I have a LOT of flights on the LA 46,, I was using a .275 venturi ST needle, 10 22 fuel,, and an APC 12.25 x 3.74 prop in almost every case,, no extra shims,,

I used to run the APC 12.25 x 3.75 and 11 x 4 and had similar launch revs to yours but it kept doing the cut out thing and i thought it was having fuel draw probs so i tried a lighter smaller prop to get more RPMs. i was suprised at the 11,400 launch too but it actually ran really well and pulled really hard...right up to the cut out at the clover! I think I will hit the reset button like mentioned above and go back to square 1...take out the shims and go back to a more 'known good" prop and try kicking out the tank back a little more. I use that rubber tool bed liner that looks like big sport shirt mesh to kick out the back of the tank, it makes good vibration damping and i just 'roll' up the back to make a bump out and it may have "flattened" out or squished...matter of fact I just looked and it has...gone flat as a pancake. Need to re-think that stuff. looks like the fuel attacked it and it is getting very soft...

I agree with Brett,, however one other thing I experienced with the LA having exactly the same symptoms on my profile Gee bee... I found that I was flying with the airframe yawed out ,,

   That certainly makes it worse. It yaws nose-in (or less nose-out) as the fuel runs out, of course, which helps.

     Brett