Popping through exhaust on acceleration

[polarnj]

1969 with 383 and Edelbrock carb. It was previously doing it maybe 1 time per ride, now I took it out yesterday and it was doing it the whole time (about 25 minutes)

Anything more than halfway down the gas pedal it pops several times through the exhaust when accelerating, and then it goes on its way until the next time I press the gas more than halfway down. Doesn't seem to be an issue at idle.

When it happens you can kind of feel it loading up before it does so.

Choke is disconnected and according to the PO I have no thermostat either. Could it be that it's because it's so cold outside? Temp was in the lower 30s yesterday.

However, my ride home going the same distance it suddenly started running better, which it sometimes does.

 

[Davea Lux]

Start by installing a new thermostat. It is important to have the engine at proper operating temp to get the proper burn ratio in the cylinders. If the problem persists with a new thermostat, run a compression check on all cylinders and report back.

Dave

 

[polarnj]

About the thermostat, my mechanic said I might have one after all, since I do get some heat and the gauge moves a little bit from the C mark. If I didn't have one, would I get just cold air when putting the heat on?

 

[Boydsdodge]

What your mechanic is saying is not how you check if a car has a thermostat. Drop some coolant, remove hose from thermostat housing and look if you have a thermostat installed.

 

[polarnj]

What your mechanic is saying is not how you check if a car has a thermostat. Drop some coolant, remove hose from thermostat housing and look if you have a thermostat installed.

I was going to but he hesitated and said the bolts were very stuck and I might break the water pump housing so I decided to leave it alone for the time being. It's not a daily driver so will only be an occasional ride until the car show season comes back.

Would that affect the way it runs and cause misfires etc., or does that sound more like a carb issue?

 

[70 Sport Suburban]

My 70 wagon with 383 was doing that I'd check the cam mine was warn out.

 

[CBODY67]

How long since you last bought fuel? One time I got a flaky load of gas. The car acted different and had a louder, hollow sound in the exhaust. Had to foot-throttle it to keep it from dying at red lights and such. I ran that tank of gas out of it and the new gas (from a known-good station) fixed it.

I suspect you'll break the thermostat housing bolts before you crack the housing the thermostat/water pump is located in. BUT . . . drain some coolant out and remove the upper radiator hose at the thermostat housing. You can then look into the housing to see if a thermostat is there. Either by feeling for it or with a borescope.

Happy Holidays!
CBODY67

 

[Imperial Pete]

Change the Spark Plugs. Just had that happen to a 318 Poly, plugs looked new.

 

[polarnj]

Change the Spark Plugs. Just had that happen to a 318 Poly, plugs looked new.

Sounds like the easiest way to go, it does run shaky at idle as well, though not a rhythmic shake, more of a random thing.

 

[polarnj]

How long since you last bought fuel? One time I got a flaky load of gas. The car acted different and had a louder, hollow sound in the exhaust. Had to foot-throttle it to keep it from dying at red lights and such. I ran that tank of gas out of it and the new gas (from a known-good station) fixed it.

I suspect you'll break the thermostat housing bolts before you crack the housing the thermostat/water pump is located in. BUT . . . drain some coolant out and remove the upper radiator hose at the thermostat housing. You can then look into the housing to see if a thermostat is there. Either by feeling for it or with a borescope.

Happy Holidays!
CBODY67

I've gotten gas a couple of times, although it was pretty low before. I'm now at about halfway up the gas gauge

The therm housing area is a bit coolant-corroded/greenish from a slight drip at the bottom of the hose, so I was being careful not to have anyone break anything.

How far down do you have to drain the rad? I would guess about under where the hose is?

 

[mr gtx]

do you have a spare coil to try ?

 

[detmatt]

Timing chain is the first thing that comes to my mind.

 

[CBODY67]

How far down do you have to drain the rad? I would guess about under where the hose is?

Probably about a gallon, as the total OEM-construction radiator typically holds about 1/2 of the total cooling system's capacity in coolant. Might be a good time to change the upper hose, too. High-efficiency aluminum radiators usually hold less.

The cast iron thermostat housings will usually corrode/degrade but not break over time. IF there is dimpling of the metal, you can apply high-heat silicon-type sealer to that area, skin coat, smeared on with a finger, to help fill-in the uneven surface, many times, as you then seek out a new one AND formulate a plan to change it.

It might also be that the surface 0f the hose sealing area can be cleaned up with a file, as most of what appears to be corrosion could be hardened dried coolant. Then the sealer could not be necessary.

Take care,
CBODY67

 

[wyrmrider]

plug wires can do it too

 

[mr gtx]

Yes it could be plug wires. just pop the hood at night to check the wires you will see them arcing.

 

[413]

How long have you owned this car. How are the tune up parts? Wires, cap rotor plugs? Points or electronic?

With no choke it's easy to fowl plugs on a cold start.

I had a misfire on a cylinder and plug loading up and it would pop out the exhaust. A Bad plug wire did it.

Do you have an infrared temp gun? Start cold engine and let run a minute, shut it off and check temps at cylinders on exhaust manifold near head. Now do you have one colder than the others? That's the problem one.

Remove radiator cap from a cold engine and start it up, the water in rad should be still with a t stat, and it will be flowing when cold without a t stat. It will build heat without a t stat but it will take some time in 30 degree temps.

 

[Northcoast300h]

Mine was popping due to an overheated coil. Ran great when cold or short trips. Noticed on highway once day, pedal became more sensative, like it was bogging out each time before it popped. Finally blew off the muffler on the highway with a big "boom"! then engine turned off. Came to a stop on the side of the highway. I couldn't touch the coil. It was sizzling. An hour later, I limped it back home and change it to a lower resistance coil. That was 10yrs ago and still works.

 

[SIPLOWGUY]

Sounds like ignition

 

[polarnj]

How long have you owned this car. How are the tune up parts? Wires, cap rotor plugs? Points or electronic?

With no choke it's easy to fowl plugs on a cold start.

I had a misfire on a cylinder and plug loading up and it would pop out the exhaust. A Bad plug wire did it.

Do you have an infrared temp gun? Start cold engine and let run a minute, shut it off and check temps at cylinders on exhaust manifold near head. Now do you have one colder than the others? That's the problem one.

Remove radiator cap from a cold engine and start it up, the water in rad should be still with a t stat, and it will be flowing when cold without a t stat. It will build heat without a t stat but it will take some time in 30 degree temps.

I've had it about 2 months. It has the Mopar electronic ignition, so no points. Haven't checked the dist cap or rotor yet.

Thx for the radiator info, so if the coolant is moving when cold there's no tstat? How long would it take to build heat in 30-ish weather? My temp guage barely goes above the C, even after driving for 20 minutes, but when you park for a few minutes and turn the key it goes up higher

 

[polarnj]

Sounds like ignition

would that be ignition related if it doesn't do it when you Rev it up in park, just when accelerating?