Tuning Help Needed

[colnago]

Okay, I'm trying to dial in the old girl. I'm really close, but I still have some questions. First, this is what I have:

- 352FE, rebuilt ~2,000 miles ago
- Engine Pro RV cam
- Edelbrock 1405 4BBL carb, with adapters to size the primary side to 500CFM (so I'm using the 1404 charts)
- 16Hg vacuum at 2,200-ish altitude
- Recurved Duraspark distributor with 20 degrees (crankshaft) mechanical advance, in by 3,500RPM
- 24 degrees initial advance (which sounds insane, but that's her "happy zone"), no pinging
- Idle screws out 1-1/8 turn
- Idle RPM in Park at 600.
- Distributor hooked up to ported vacuum

Okay, I've read that if the screws are out less than 1-1/ turns, then try a smaller jet. However, the plugs are grey, with maybe a touch of tan. So, too rich, or too lean? Do I believe the idle screws, or do I believe the plugs? I tried smaller needles, and it ran like crap. Should I try smaller jets, and bring the idle screws out?

Obviously, the total advance is 44 degrees. Again, no pigging, but this could be due to the low compression ratio. If I retarded the distributor, the vacuum went down and the needle started jumping. Bring it down, but hook the distributor to manifold vacuum?

Suggestions?

Joseph

[Ranchero50]

Pick up a decent o2 sensor and gauge, then you'll have some idea how the engine is processing the air / fuel during different conditions. There's what, nine different conditions the carb needs to provide for.

Cold start, warm up idle, warm start, hot idle, part throttle acceleration under light and heavy load, WOT under both, coast and over temp too. The fuel circuits all overlap so you need to know what does what when and it's easy to get sideways. You're close, don't nuke it.

Plug reading might tell you what was happening ten seconds before you shut the engine off. I had a crappy Autometer gauge and old Bosch o2 sensor setup on my blown through 600 DP Holley twin turbo'd 351w Capri and it worked well enough to know what was going on. Excellent learning experience too.

[colnago]

Does the sensor "port" just get welded into the exhaust? I assume the closer to the exhaust manifold, the better. Does it matter which side? Any brand recommendations for the sensor?

I've been told that you should shut off the engine, coast to a stop, then pull the plug. I've also been told that with today's gas, reading plugs is somewhat unreliable. Maybe an O2 sensor is the way to go.

Joseph

[Ranchero50]

Yes to all of it. You can buy the bung, drill a hole in the pipe and weld the bung in place. For brand, Bosch spec'd for a fox mustang always worked well, Ford P/N ones out of 2.3l stangs and Rangers responded faster than the aftermarket stuff. You really don't need a wide band, the narrow will tell you what's going on enough to tune it and costs a fraction of the cost.