Popping... then backfire

[Stephen Ford]

Getting this popping noise on the left bank. Doesn’t seem to start until the engine is hot.

After we shut her off she backfires.

Plugs, plug wires, and distributor are new. Double checked the plug connected.

There is a crack in the exhaust manifold on the left bank I can see the engine firing through. Not sure if it’s related.

Any ideas? My dad is wondering if we have a valve sticking at this point cause we checked all we could with the ignition system.

 

[moes]

it is your exhaust manifold causing your problem. The reason you hear it after the car get hot is the crack in the manifold is starting to open up from the heat, when the manifold cools down the crack closes up. The expansion in the manifold crack takes place when it is hot.

 

[oldbee]

Yup, air getting in there!

 

[MoparLeo]

Don't wait to fix it. Nothing but bad will come from procrastination.

 

[Ironbuilt]

Try re-torquing the exhaust manifold bolts to spec. Should help.

 

[Stephen Ford]

We’ve ordered a new manifold already just cause we don’t want a cracked one.

I asked my dad if that could be the problem but he’s telling me the thing would run fine without the manifold on there at all so he doesn’t think that’s the case.

He’s trying to argue that the exhaust valves are expanding with the heat and sticking.

We’ll find out I guess.

 

[miller]

Just so your straight on things, yeah, positively need to repair/replace the manifold.

Without the manifold...if engine was run for much of a length of time, results would be valves would start to burn. Any gas engine with valves, needs an exhaust system, at least 6" from the valves, a path for the flame front.

(On radial engines, we used 8" exhaust stacks.)

 

[747mopar]

Since it's already ordered it only makes sense to replace the damaged manifold before going any further but my guess is that's it. Another common cause for run on or backfires after shutting the motor off is carbon buildup, the carbon becomes red hot and will act like a spark plug igniting the fuel.

 

[moparcrazy]

obviously fix the manifold , but I have to agree with your dad, sounds like a valve is sticking.

 

[69b3rt]

I would pull valve covers off and check valve springs. Maybe a broken or weak one.

 

[Stephen Ford]

I would pull valve covers off and check valve springs. Maybe a broken or weak one.

That’s what we’re thinking. We’re gonna do that and replace the cracked exhaust