I just finished reassembling my 350 i finished putting on the Long Tubes, old rebuilt Holley 4160 carb, new wiring, new plugs, coolant, etc..
i get a lovely rumble on idle with open headers but theres this noticable crackle in the exhaust on idle.. i adjusted timing and idle speed and it's still there... what could be the problem? i replaced the cap on the dist because it had carbon tracks on it.. could there be something else wrong with it? it's an HEI distributor..
seems to run fine other than that.. with the exception of i had to turn the idle up.. and if i take the vacumme brake hose off the carb and leave it open the engine perks right up using the old idle settings.. almost like it's not getting enough air.. i havn't put the air cleaner on yet. one interesting thing, when i was pulling plug wires one by one while it was running, trying to trouble shoot the exhaust crackle.. one post gave me a slight tickle where as another one gave me a heafty jolt...
thanks for the help..
~J

 

That's tought to diagnose without hearing it. Can you record a
sound clip?

This "crackle" that you describe...does it occur randomly, or when
you press the throttle down momentarily and let off?

What is your base timing set to at the moment?

 

popcorn in the pipes???? MAYBE I DUNNO

 

is it like a fire spark type sounds.. or a light clicking?

have u checked ur exhaust gaskets? u may have a leak.

other then that... check ur plugs make sure there not touching at header tubes.. or anything like that.. may be arching??

 

If the sound you hear is "popcorn popping" and you don't have
any leaks...everything is fine.

That sound is the valves closing. It's more pronounced now
because of the long tube headers. I heard a distinct change
in my tone when I changed to a heavier spring.

Would you happen to have 'true' dual exhaust? It would really
become clear if you did.

 

You're running the car straight through open headers without exhaust pipes or mufflers and you're wondering why you hear a "crackling" noise?

Excuse me, but...

I'm sorry, but even my kid could figure that one out!

Hook up the damn exhaust system!

 

why?

there is no problem running open headers?!?!

i run a 3" cutout off the headers and i do not get any cracking/popping sound.

open headers rock the party