I just picked up the car tonight and drove it 50 miles home. The guy had the motor swapped in, put about 2K miles on it, then it's been sitting for over a year. He said it never really was tuned properly. I know the timing is advanced too far because it diesels when you turn it off. Things I noticed on the way home:
-Bucks at really low rpm when slowing for a stop.
-Kinda erratically misses when above 4000 rpm when accelerating hard.
-Takes off really strong, then it seems not to rev very fast to the upper rpms.
-Temp stayed about 170 cruising most of the way home, then a few blocks from the house had climbed to ~215. Shut it off, with just key on, only the driver side fan was running.
-SES light stays on.

The timing marks on the balancer are painted green marks. If your facing the engine there is a groove across the balancer, then clockwise, 4 green marks, large green mark, then 3 green marks. Which of these marks should I line up in the v groove attached to the motor? Is this normal?

What is the brass like ~3/4" nut with a wire connected, positioned midway on the block, pass side below headers? This wire was loose, and came disconnected with me just touching it.

What plugs should be installed?

I want to check the IAC and TPS, but I thought I would set the timing first. The car runs smooth as silk on the highway with AC and cuise control on.

The details:
ZZ4 w/TPI, LT4 hot cam, ported heads, roller rockers, Edelbrock TB, larger runners, ported plenum, headers, full exhaust, aftermarket chip(brand???).

Sorry so long, but this is going to take me awhile to come up to speed and get this thing tuned out. I've got alot of experience with mustangs and I've been reading this site for a week now trying to learn. Thanks for any help you give me!

Steve

 

lot of questions
i'd look at another SBC to get an idea of how and where the timing marks are and relate them to your engine. set the timing with a light with the ESt unplugged. the nut with the wire is the knock senser, very important part. the ses light will stay on with KOEO and one fan should run with KOEO.

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ICON Motorsports

1st & 3rd
MM Black Diamond 538 F&AM

 

running rich can cause many of your symptoms...

 

Running rich makes sense and there is dark brown smoke at WOT. Now if I can figure why it's running rich.

 

The knock sensor being disconnected will cause a constant check engine light. If the plug on the end of the wire is mashed up and won't stay on you can buy a new plug at a good auto parts store that has an automototive specialty electrical connector section. I found all kinds of hard-to-find connectors like this at one of my local stores. If you don't see it on the shelf, ask to see the catalog and you'll be able to order it.

As for the top-end miss and other drivability problems I would recommend begging/borrowing/stealing a diagnostic tool like a Diacom setup or other similar. You can't tell jack squat on a modified engine until you see what the computer is seeing. That's probably one of the reasons the guy you bought the car from only put 2K on it- he couldn't figure out all the little gremlins himself and got frustrated.

Make sure there are no exhaust leaks anyhere near the headers before you start trying to diagnose anything. Exhaust leaks play havoc with the O2 sensor (reads too lean so the ECM fattens up the mix) and that's a critical sensor on an EFI motor.