Cuda 340 engine issue....maybe

[Kansan]

Hey guys, I'm having an issue that just started on my '73 'Cuda 340 automatic. The last two times I've taken it out (about a week apart) I've noticed once I get down the road a couple of miles and the engine is good and warm, the engine will start making a chugging noise on acceleration. Kind of sound like an exhaust leak, but only on acceleration. Steady RPM, nothing. Today, it would sometimes stumble when it was making noise. Let off the gas and it was fine. It is very rhythmic and doesn't get faster at higher RPMs, just louder. After four or five miles, it stops and the car runs just fine. It's been quite a few years since I've messed with an engine other that some routine maintenance. I know it is a shot in the dark, but any ideas are appreciated.

Thanks,

Kansan

 

[pschlosser]

If the rhythm is more or less constant, and goes away a while after starting, I'm thinking something related to the choke, and/or carb heat system. A picture of your engine would answer some questions about which air cleaner, and your engine setup.

 

[Kansan]

As requested....the noise is mainly aural, but I can maybe feel a little bit in the car except the couple of times in stumbled, almost like it is running out of fuel. I have had the car about four months and have driven it weekly, at least. The last two times are when I've had the issue....

 

[pschlosser]

if you have a vacuum gauge among your tools, you can hook one up for a few days, and position it to view as you drive to get a feel for what is normal vacuum under varying conditions.

when I think about what changes between a warm engine versus a cold one, there is definitely tolerances all over the engine. but the choke system is only active when it's cold. and that valve on the snout of the air cleaner could be changing the sound you hear. Or the heat riser (the bimetal valve on the passenger side exhaust manifold) doh, but you may have headers, so it's not that.

if you flip over the air cleaner lid, this will also change the sound of your engine. Try that, too, and tell us if the sound seems similar to what you hear when it's cold.

 

[pschlosser]

Thanks for sharing the images of your engine.

My next two comments are NOT related to your problem. But I see a couple things you may want to add to your TODO list to improve. Refer to the image.

You want a throttle cable bracket that positions the cable so it is more inline to the attachment point on the throttle lever at the carburetor. See how yours has to bend to make the connection point? I think this can prematurely wear your throttle cable and cause failure. If possible, you can try using a different connection point to bring it more inline with the cable hold-down.

Also, you seem to be missing the Transmission Rod Return Spring. This spring returns the throttle pressure when you let off on the gas. This is helpful when going from WOT (wide open throttle) back to idle or partial throttle. Maybe you simply need to re-task and move that second one piggy-backed onto the throttle return spring.

 

[Kansan]

but you may have headers,

I do.

Thanks for any feedback...that is why I posted. My last MOPAR was a '69 Sport Satellite 383 2bbl back in the mid-80's so I'm a bit rusty on these things....

Kansan

 

[Kansan]

Also, you seem to be missing the Transmission Rod Return Spring

Awesome information....i actually didn't notice this....Probably why the kick-down felt weird. The situation has been corrected.

Kansan

 

[moparleo]

From the Factory Service Manual. Use it.
If you don't have one here is a site for free downloads,
Resource Library – MyMopar