last night i was drivin the beast around, and started gettin a compressed air sounding noise from the carb, it was too dark to see so i left it overnight, came back in the morning and sure enough, i got a harsh backfire comin from the carb that stops backfiring when its reved up a bit and held there, but if its idling or given any more gas, it backfires again.
basicaly.. motors goin

chug chug chug chug chug chug chug chug

backfire sounds like

pop........pop........pop.........pop

its always there

I cant get rid of it, havnt taken the carb off or apart or anything, i need ur guy's opinion on what could be makin the sound and also how to fix it.

here's a picture of the carb

http://holley.com/HiOctn/ProdLine/Pr.../f0-4609-1.jpg

its a holley 750 Vaccum Secondary model 4160

the car specs are :
----------------------

Big Block 402 from a 396
11 to 1 T.R.W Pistons
Steel Crank
530 Lift Hydraulic Cam
Closed Chamber 219 Intake
1.88 Exhaust heads
Fully Polished and Ported
Edelbrock Performer Intake (Match Ported)
Holley 750 Vac. Sec.
Super T-10 Aluminum 4-speed manual transmission
Hurst Shifter Kit
10bolt 3.73 Posi rearend

 

Try advancing the timing a little. If that doesn't help, sounds like it might have broke a valve spring on an intake valve.

 

The "compressed air" sound might be a vacuum leak. Get a can of carb cleaner and squirt it around carb and intake. Whenever idle speeds up, that is the area of leak. If it happened suddenly, suspect a hose or plug that popped off a fitting on carb. If it's around base of carb, a section of the base gasket might have gotten sucked in or the base itself might have cracked.

If the "compressed air" sound is coming from the carb throat, then you might have something causing engine to spit up the intake tract. Do a compression check to see if one cylinder is down on compression.

 

its a friends car i know.... and i just read the post... hes quite the dumbass... and the compressed air sound he was hearing, was the carb sucking the air