I bought a 77 280 from a guy that had not touched the car in several years. At some point, someone did a carb conversion to dual SU's (looks like they came from a 72 240.

I did the usual stuff to a car that hadn't been started in 4+ years. Drained the gas, replaced the fuel filter, cleaned the plugs, replaced the starter and cleaned the carbs and changed the oil & filter. Also replaced most of the fuel lines and had to rewire the fuel pump.

After all that, the car actually would start and run decently (backfires inconsistently), but as soon as the engine is under any kind of load - it hesitates severely and had very little power.

The distributor is advanced as far as it will go (retarding it makes it run worse at idle). I also noticed today that the vacuum line to the vacuum advance on the distributor is not connected.

Any advice on what I need to check next? I think the carbs are getting enough fuel (revving at idle seems OK). I am a little concerned that the distributor is fully advanced (maybe the dizzy is off a tooth?). I haven't bought a timing light (in the past, I just power timed my cars), but it looks like I may need to in order to verify the timing if indeed still way off.

I took some pics of the dizzy area and also am attaching a pic of the intake and carbs to see if someone can spot something off.

This is my first carb'd Z (all the others were 75-78's with FI), any advice or help is greatly appreciated.

LJ Wilson

 

Welcome to Zdriver man.

As for the dizzy, on my 280zx. There is an adjusting plate underneath it. You may need to move it. On mine it is a 10mm I think. I discovered this, when I was screwing with my timing a short while back. Anyway, if you move it, you may be able to advance it more. But yes, I would invest in a timing light. I got mine on ebay a few years ago, for pretty cheap. And it is a Craftsmen one. Good luck.

 

It sure sounds like two plug wires are crossed. The #1 wire should be at the 9 oclock position on the dizzy. Without vacuum you have no advance.