Hey guys:

I recently got back in a slant, a '68 Valiant . It's been off the road for several years, and when I got it, it ran rather poorly. The tank and carb had water and rust in them, so I replaced the tank and rebuilt the carb, along with installing a new fuel pump since the old one quit.

Here's the head scratcher....it still runs pretty rough. At idle, it runs unevenly and the exhaust smells rich. The mixture screw has no effect turned all the way in even. It does not have a dead miss and compression sounds good just listening to the starter.

So, I started diagnosing. I put the timing light on it and at about 800 rpm with the vacuum advance blocked, it was about 13 degrees ATDC....AFTER top dead center. I loosened up the bolt on the distributor, got it to move finally, and inadvertently turned the distributor counter-clockwise. I fired it up..and it ran BETTER, with the timing even more retarded. The idle smoothed out and the mixture cleaned up. That was about 16 degrees ATDC, as far as the distributor would turn. I realized my mistake and advanced the distributor back past where it was, and it ran worse again. With the distributor at full advanced it's not even coming back up to TDC where it should be timed at. It starts easily. Even with the timing retarded as far as possible, the engine doesn't run perfectly..it still has a periodic surge after you bring it up off idle.

I learned long ago to not blame the carb for what seems to be a carb problem, so right now I'm ruling out the carb. The only other thing going on is the shim gasket between the intake and exhaust is blown out, and with the timing in it's original position(halfway through the adjustment slot) you can hear a random backfire in the manifold...just like the timing is late.

I've had several slants and other mopars and know my way around them pretty well, but all of them had electronic ignition. The last slant I had with points was 22 years ago. So, I am weak on the entire points, dwell angle, timing relationship if that's even a factor here. I have not adjusted the valves yet.

I'd welcome any tips and advice before I end up going down a rabbit hole on this. Thanks again.

_________________
1966 Chrysler 300 coupe
1968 Plymouth Valiant 100
1969 Dart Custom 273 V8

Adjust the valves.

While you are at it make sure your timing mark on the damper is where its supposed to be.

Check for timing chain stretch.

_________________
Yeah....Im the one who destroyed this rare, vintage automobile.....

The rotor in the distributor rotates clockwise...rotating the distributor body itself counter clockwise advances the timing ... if you turn the body clockwise and it retards the timing....

On the timing tab on the late spotwelded tabs BTDC is to the passenger side of the tab from 0.. and the drivers side is of course After TDC...

Depending on the timing curve of the distributor about 13-18 deg. advance at 900 rpm idle is about right...

There can be some other factors here as well... you will have to run the #1 piston up to TDC on compression stroke and check your damper to see if the TDC mark is still accurate... typically the damper rubber lets the outer ring slip and your timing mark will be off... making it hard to accurately set the timing and see where it lands....

If it's reasonably accurate for TDC, roll the crank back to 8BTDC and set the distributor there, then run it and see if that better (that being said the points and condensor may need to be replaced (about $12 +/-) and you'll have to remove the dizzy...

You should also get the valves adjusted and see if it runs better...you might also see if any of them are sticking...

Another worry is the timing chain... if you are advanced a lot and still ATDC and you know the damper is good... then the timing chain could have been loose and skipped a tooth... points are a bit more tolerant to a loose chain than EI set ups are.... the best way is to pull the plugs and pull the dizzy cap... and roll the crank back and forth and see if the rotor sticks/doesn't move after a change in direction...

Hope that helps. Keep after it, you'll get it licked!