Exhaust

[Hottrodder427]

Is it normal for the engine to pop through the side pipes when cruising in 3rd or 4th

[CraigS]

No. But can you supply a few details please. Also you might add intake system details to your signature line.

[Hottrodder427]

Edelbrock performer rpm intake and Holley 850 cfm carb, it's not a constant popping

[Gumball]

Does it sound more like an "after fire" where unburnt fuel is being lit off in the header?

Possibly look for a miss, including checking spark plugs and wires. I had an intermittent miss in mine that got progressively worse - sounded like a dull thud through the exhaust when it would occur - and the source was plug wires that were cracking as a result of overheating from the headers.

[Mesa Mike]

Make sure your header bolts are tight

[Raceral]

Triple check to make sure your plug wires are going to the right plugs... Mine did exactly the same thing many years ago...

[Jeff Kleiner]

If it only occurs when you let off of the throttle the most likely cause is leaking header or collector gaskets.

Jeff

[j.miller]

I'm with Kleiner,,, I think you are sucking a bit of fresh air through the collector gasket.