Light throttle ping from stoplight on hot days

[Voeltagear]

At this point I've replaced every piece of rubber fuel line, the sending unit, the fuel pump, fuel filter, re-routed the fuel line from the pump to the carb, repaired the steel vent line back to the tank, cleaned the idle/low speed jets, added a little extra shot to the accelerator pump, and double/triple checked the float level. I'm still having issues with the idle leaning out after a while and intermittent pinging in second gear. The A/F ratio when it pings is in the mid 12s:1. A couple of snaps of the throttle will correct the idle mixture sometimes but other times it will revert back to lean. I'm stumped at this point. I was hoping to have the issue diagnosed prior to putting the 4bbl on but at this point I think I need to replace the intake gasket just for piece of mind so I may as well do the swap. I've sprayed carb cleaner around everything on the outside with no vacuum leaks found.

 

[Voeltagear]

It's numbers matching carter bbd. I'll hook up a fuel pressure gauge this week.

It runs a pretty steady 3.5psi but I didn't take it out for a test drive to see if it changes while cruising.

 

[Voeltagear]

I got fed up last night a started to take the carburetor off to clean it again. Just out of curiosity I pulled one of the rubber vacuum caps and stuck it on my vacuum pump. The s.o.b. was cracked and leaking. It wasn't visible and never showed up when spraying it with carb cleaner. Well now the idle mixture stays steady.

 

[AMC Diplomat]

I got fed up last night a started to take the carburetor off to clean it again. Just out of curiosity I pulled one of the rubber vacuum caps and stuck it on my vacuum pump. The s.o.b. was cracked and leaking. It wasn't visible and never showed up when spraying it with carb cleaner. Well now the idle mixture stays steady.

Simple things sometimes

 

[Voeltagear]

Anyone have experience with tuning timing curves? I adjusted my heavy spring to slow the curve earlier and it helped a lot with the pinging but I'm not satisfied with the power curve. I'm currently running 8° initial plus 22° mechanical advance and 10° vacuum advance. It hits hard early but drops off sooner than I'd like. I'm hoping to get to 32-34° total mechanical advance. I'm planning to plot the advance curve next weekend and I need advice where it should be for a stock 318.

 

[Voeltagear]

After looking further into my distributor I believe it has 13° of distributor mechanical advance. So it should have 26° of mechanical advance. 26°+8°= 34°, right where I want to be. I may try an old Mallory unilite distributor I have. It has adjustment for the mechanical advance and springs are readily available.

 

[Voeltagear]

I'll give the mopar ignition module credit. I swapped in a gm hei module and the car died today after a good heat soak. It turned out to be a weak signal from the magnetic pickup in the distributor. A couple thousandths was the difference in a no spark, no start situation. The mopar module never gave me an issue.

 

[AMC Diplomat]

I'll give the mopar ignition module credit. The mopar module never gave me an issue.

 

[Remow2112]

Check out 4 seconds flat. They sell a plate that goes in stock mopar distributors that limits the mechanical advance.

How to limit mechanical advance in a mopar distributor, tuning for street, strip or all out racing, cure that rich stinky idle, win races

 

[Voeltagear]

I installed my backup distributor today and recorded some timing numbers with the vacuum can disconnected. Factory Green light spring and Brown heavy spring.

No mechanical advance to about 900 rpm.
4° at 1000 rpm.
11° at 1200 rpm
15° at 1400 rpm
Then it stalls until about 1900 rpm
17° at 2000 rpm
21° at 3000 rpm.

 

[Voeltagear]

Also, I ordered a limiter plate. Looks like my light spring is pretty fast and the heavy spring maybe too slow?

 

[Voeltagear]

Things are looking up. Fingers crossed I've resolved a couple of issues this past couple weeks. The vacuum cap that was leaking fixed the leaning out when hot issue. I also discovered the vacuum advance hose was delaminated and I think it was collapsing inside not allowing it to release the vacuum advance. I think it was staying advanced when I would release the throttle causing it to ping on tip in. The other thing I did was run a bottle of Chevron with Techron through a tank of gas. I have a feeling it freed up the rings. I have consistent compression on all 8 cylinders now where I had 3 that built compression slowly before. Currently the initial timing is set to 6° + 26° mechanical and I'm running 89 octane fuel with no pinging in 80°+ weather. It runs strong enough and I can merge into 70mph traffic with ease. (Which wasn't really ever a problem except the pinging which resolved by letting up a little) I'd like the heavy spring to be a little lighter so the timing was all in by 2200-2500 but it works for now.

 

[OLDIRON]

Congratulations on the tune. I know it's a rigmarole, but necessary.
I was able to tune my 75 Dart BBD catalytic 318 auto 2.73 rear to run well with ported or constant vacuum advance. Different tune for each.
Best all-around setup on this car is with "working egr" and ported advance. 3 mpg difference at 60/70mph. 14 to 22 mpg overall. Same acceleration and idle. Accelerates smartly at 50% throttle. 87 e10. Full throttle acceleration? Well, no cfm, no cam, no impressive acceleration. Stone cold dead at 4800 rpm.
Thinking about trying the bigger BBD for the 383.