Light throttle ping from stoplight on hot days

[Voeltagear]

I have a 1976 Dodge Aspen with a 318, 4spd. Since the weather warmed up this week into the upper 80's I've been experiencing a light throttle ping when leaving a stop light. It gets progressively worse as under hood temp rise.

The EGR was deleted by a previous owner. Short of replacing the EGR system what are some tips and tricks to lower the intake air charge and Cyl temperature? Coolder plugs? Snorkel? (My car doesn't have a provision for the paper tube). More fuel from the accelerator pump?

I've checked the temperature at the Thermostat outlet (194°), water pump inlet (147°), Snorkel (130°), and EGR block off (230°). I have an electric fan which is running at idle and the center of the radiator is 115°.

Any ideas are appreciated. Thank you.

 

[Mikes5thAve]

First thing to check is the timing. In addition to timing if it still has lean burn my 79 360 had a problem with the computer not working properly causing it to ping.

 

[Voeltagear]

The timing is 2 degrees ATDC at 650 RPM and vacuum disconnected. It runs terrific. I've tightened up the vacuum advance spring to bring it in slower but it still does it, even without vacuum advance hooked up. And it has a lot less power under light throttle. Boo. Under 80-85° ambient temperature it isn't a problem. I'm almost certain it is the air charge temperature that's the problem because it only does it after a complete stop, the longer the stop the more pronounced it becomes. It does not happen at roundabouts or very brief stops. With the EGR delete it almost always a problem on these low compression motors. I don't believe lean burn was around in 1976.

 

[Camtron]

What carb? Bigger jet, lighter springs, smaller needle…sounds like she’s not getting enough fuel from you’re posts above…edit: also the basics, clogs, collapsing fuel lines, dirty in-line filter if you got one. Maybe time to clean/rebuild the carb if it’s not been done in awhile.

My o2 sensor is currently burnt out but, it’s pretty easy to plumb an o2 sensor and air/fuel gauge and take all the guessing out. I just used a cheap Bosh kit from Amazon.

 

[Aspen500]

Keep in mind that gasoline is formulated for EFI and is more prone to pinging with a carb due to vapor pressure, volatility, bunch of scientific jargon, etc. It's made to work at 50 or 60 psi or more, not 6 psi.

Getting outside air to the carb would help. 85 degree air is much better than 150 degree underhood air to reduce pinging.

If all else fails, try using 89 octane instead of 87 and see if it helps or not.

 

[Mikes5thAve]

ATDC doesn't sound right. How does it run if you leave the distributor vacuum disconnected?
I've never found much difference with egr deleted. Usually on older engines it's blocked up with carbon anyway.
You could also try a different brand of gas. Sometimes that's enough to make a difference.

 

[Voeltagear]

The carburetor is a Carter BBD, all stock parts rebuild last summer. Fuel filter is new a couple weeks ago. The fuel formulation is a curious thought. I've been running 89 octane so I could try recreational fuel, 91 octane. Not a fan of the upcharge though.

I've gone through many tests with the timing. Anything 0° or BTDC causes pinging with or without vacuum advance. Especially in second gear. Different distributors with different total mechanical advance, different springs and with or without vacuum advance. I haven't put the piston stop in and checked the marks. It runs "OK" at 4° ATDC but it looses a step. I really don't care what the initial setting reads at this point. The car runs fantastic in all conditions except very hot days after sitting at a stop light.

 

[Voeltagear]

ATDC doesn't sound right. How does it run if you leave the distributor vacuum disconnected?
I've never found much difference with egr deleted. Usually on older engines it's blocked up with carbon anyway.
You could also try a different brand of gas. Sometimes that's enough to make a difference.

Runs the same under WOT. Less pep at part throttle.

 

[Voeltagear]

What carb? Bigger jet, lighter springs, smaller needle…sounds like she’s not getting enough fuel from you’re posts above…edit: also the basics, clogs, collapsing fuel lines, dirty in-line filter if you got one. Maybe time to clean/rebuild the carb if it’s not been done in awhile.

My o2 sensor is currently burnt out but, it’s pretty easy to plumb an o2 sensor and air/fuel gauge and take all the guessing out. I just used a cheap Bosh kit from Amazon.

If it were lean wouldn't it do it no matter the temperature? Especially a cold engine after the choke opened but it wasn't at operating temp? As it is it runs absolutely perfect in all other situations except hot days after a stop light it pings briefly.

 

[Camtron]

If it were lean wouldn't it do it no matter the temperature? Especially a cold engine after the choke opened but it wasn't at operating temp? As it is it runs absolutely perfect in all other situations except hot days after a stop light it pings briefly.

No, not particularly. If it’s lean because of the mechanical set up of your carb due to bad set up/tuning or because some tuned it for cold weather, you can have lean and rich spots in your circuit as you advance the throttle, vacuum, timing ect…again, I’d plum in a air/fuel gauge and take out the guess work of what’s happening when you hit the gas pedal off a stop.

 

[Voeltagear]

Keep in mind that gasoline is formulated for EFI and is more prone to pinging with a carb due to vapor pressure, volatility, bunch of scientific jargon, etc. It's made to work at 50 or 60 psi or more, not 6 psi.

Getting outside air to the carb would help. 85 degree air is much better than 150 degree underhood air to reduce pinging.

If all else fails, try using 89 octane instead of 87 and see if it helps or not.

Is there such a thing as a fuel line cooler? Right before the carb seems like a good spot.

 

[Aspen500]

Was going to mention checking the balancer but you beat me to it!

This is only a possibility. Does the engine burn excessive oil? Just going by the circumstances, if the valve guides and/or seals are bad, the high vacuum at idle can pull oil past the intake valve stems. Oil will burn hotter and than gas in the combustion chamber and ping when accelerating from a stop under high load. Ran into that at work a few times with vehicles that pinged, some bad enough it burned the exhaust valves they got si hot. As I said, just a possibility.

 

[Camtron]

I daily a 4barrel with no EGR all year long. 87, 89, 91; don’t matter. I don’t got any pinging.

 

[Voeltagear]

Was going to mention checking the balancer but you beat me to it!

This is only a possibility. Does the engine burn excessive oil? Just going by the circumstances, if the valve guides and/or seals are bad, the high vacuum at idle can pull oil past the intake valve stems. Oil will burn hotter and than gas in the combustion chamber and ping when accelerating from a stop under high load. Ran into that at work a few times with vehicles that pinged, some bad enough it burned the exhaust valves they got si hot. As I said, just a possibility.

It uses a half quart every 6-700 miles. Blue puff on hot start. I'm sure it's not helping.

 

[Voeltagear]

I daily a 4barrel with no EGR all year long. 87, 89, 91; don’t matter. I don’t got any pinging.

Low compression smog motor? Factory carb etc?

 

[Camtron]

Low compression smog motor? Factory carb etc?

Low comp smog motor, tuned 625CFM Demon carb and EdelBrock intake. Below freezing, 90+ in the summers, runs right all year long.
Honestly, since I’ve put the car together, I’ve never understood half the complaints people make about current gas. Just sounds like a lot of people with ignition, timing, carb tune issues. New modern carbs work fine with the current gas blends. Taking the time to properly tune jets, needles, springs, accelerator pump, ect, make a giant difference. Most people give up at basic idle, air/fuel adjustments on their carbs.

 

[Voeltagear]

No, not particularly. If it’s lean because of the mechanical set up of your carb due to bad set up/tuning or because some tuned it for cold weather, you can have lean and rich spots in your circuit as you advance the throttle, vacuum, timing ect…again, I’d plum in a air/fuel gauge and take out the guess work of what’s happening when you hit the gas pedal off a stop.

I guess my point about the cold engine choke open should have been lean miss/backfire. Which I don't have. I do have a wideband AF meter. Just need to weld in a bung. I have a feeling the chamber is to hot and not enough quench.

 

[Voeltagear]

Low comp smog motor, tuned 625CFM Demon carb and EdelBrock intake. Below freezing, 90+ in the summers, runs right all year long.
Honestly, since I’ve put the car together, I’ve never understood half the complaints people make about current gas. Just sounds like a lot of people with ignition, timing, carb tune issues. New modern carbs work fine with the current gas blends. Taking the time to properly tune jets, needles, springs, accelerator pump, ect, make a giant difference. Most people give up at basic idle, air/fuel adjustments on their carbs.

Haven't given up at all. It's a factory tuned carb for an operational EGR. The exhaust gas takes up space which, in addition to it's primary job of reducing nox, helps quench for low compression engines designed to pass emissions. I could open up the jets or maybe someone makes step up rods for a BBD. Just looking for some suggestions. That's all. Thanks for your input.

 

[Camtron]

Haven't given up at all. It's a factory tuned carb for an operational EGR. The exhaust gas takes up space which, in addition to it's primary job of reducing nox, helps quench for low compression engines designed to pass emissions. I could open up the jets or maybe someone makes step up rods for a BBD. Just looking for some suggestions. That's all. Thanks for your input.

Oh, I didn’t mean you giving up specifically, just people in general. All the years and people still treat them like a mystical item only certain wizards can work on.
Cheers.

 

[Voeltagear]

Oh, I didn’t mean you giving up specifically, just people in general. All the years and people still treat them like a mystical item only certain wizards can work on.
Cheers.

Lol