Mark Maras

Well, it would appear we're back to the rear carb. How many turns down are the mixture screws on both carbs?

I agree with Cliff. It seems to be a rear carb mixture problem of some sort. How many turns down are the nozzle screws? However, that doesn't explain #5 and #6 looking like #4. As I recall, #4 alone was the problem child. @jalexquijano What was the outcome of changing the valve seals? Was one of the seals on #4 damaged and did you change them all or just #4?

The problem I've experienced with flux core and repeated small welds is the flux left on the finished weld. When it cools it prevents instant conductivity to start the arc when doing small welds. If it doesn't arc instantly you're left with a longer wire which will act like you've turned down your welder. You'll have success if you clean each weld before attaching another weld to it. I usually try for very small gaps and I run it a bit hotter (instant arc) than I would for a continuous weld. I would also suggest the smallest wire you can find and an auto darkening hood (for precision).

I prefer flux-core for welding rusty, crusty or plated thicker steel. This paper thin sheet metal, if properly cleaned and has minimal gaps is best welded with a MIG using Argon or a Argon-CO2 mix if TIG is not an option.

.035 is the measurement that I always used. Good luck on the floats. Just for clarification, the float level doesn't have to be exact, just close. If you want it exact, the fuel level should be 3/8" below the carb bridge. That's 9 5/8 nozzle screw turns down from the top.

It may be time for a new set of BP6ESs too. I've experienced a high RPM stumble that was cured by new plugs.

Check the float levels. you may find that elusive 5%.

I don't recall any talk of adjusting the float levels (the primary mixture adjustment). The easy way to check them is remove the domes and pistons, raise the mixture screws to the top, then lower them 9 1/2 - 10 turns down from the uppermost position. The fuel level should be close to the jet height at 9 1/2 - 10 turns down. Then raise the jets back up to 2 1/2 - 3 turns down from the top. How many turns down are your mixture screws now?

I've set them cold and hot. Both methods worked for me.

That brings back the memories of my first car, a 64 Catalina land yacht.

Fun to look at but I don't care for her tunes.

I don't remember hovering on or watching anything that would explain why I'm getting Donny and Marie videos. The closest I've been is watching delta blues videos.

Early to bed and early to rise, your girl goes out with other guys.

#4 looks to be a radio bracket.

Sputtering at 3500 rpms while climbing a hill sounds like fuel starvation to me. Especially if it will rev to high rpms in neutral (no load). Fuel filters, float levels, carb balance, fuel pressure, and fuel volume, are where I'd start looking.