First off I've built many 240sx's, rebuilt many motors, tuned many cars, used to work on racecars, etc. I would consider myself to be very knowledgeable in the mechanical department, but DAMN I'm stumped, and I have never dealt with these motors before, but it seems pretty straight forward.
L26, E88 head, Round top SU's, stock exhaust, etc.
Well when I first got the car, I retuned the carbs, and the car ran great for 200 miles, then the plugs fouled. They were black a sooty, a sign of running rich, so I retuned the carbs AGAIN, and they were pretty close to spot on, then took it to a local Datsun guy who used to race these cars who made sure that the Carbs were working top notch. He made a few adjustments, but they were pretty close.
200 miles later, fouled plugs again, same thing.
I had yet to check the timing, so I put a timing light on it and it was at perfect TDC on the timing marker. Which I believe is the 2nd notch from the top, so I advanced it.(I think, I can't find any information on advancing/retarding in reference to the timing marker thingy) to the 2nd mark from the bottom, so I'm guessing that's around 15* BTDC advanced.
I retuned the carbs immediately afterwards, and now it still feels slow, and sounds like it's missing a little under full throttle.
So I'm just asking for some feedback on what this could be, what I could be doing wrong? What I should be doing? Etc, Criticism is incouraged! Poke holes in my story, poke holes in my mechanics, I really don't care, I can handle it, I would just like some insight.