Here lately when I go to crank up the motor I'm swapping into my truck it has been getting harder and harder to start (giving it more gas and more cranking tries than usual) but when it did fire up it would take the normal "warming up" to get a good lopey idle. But the last couple of times trying to start it the idle sounds terrible like it barely wants to idle. Keep in mind I haven't adjusted anything since I've had the car now for a few months and when I got it it ran fine. Well today again it took a longer than normal amount of time to crank it and when it did run (barely idleing) I would get these loud as almost dynamite explosions occasionally out of the exhaust. So loud it hurts your ears and then I just turn it off. I'm just getting into this and have no idea how to tune a carb so yea I plead dumb on my part. But what exactly is happening here? Here's the specs on the motor:

• 383ci sb
• 4 Bolt Main
• Forged Alum Flat Top Pistons
• Forged 5.7 Rods
• Lunati Hydraulic Cam 246 Duration / 520 Lift
• Camel Hump Heads
• Comp Cams Valve Locks, retainers, springs, etc.
• Stainless steel valves
• Victor Jr. Intake Manifold w/ Air Gap
• Holley 750 Double Pumper Carburator w/ 2" Spacer
• Double Roller Timing Chain
• Mallory fuel filter canister type w/ replaceable filter
• Jegs Pro Starter 4.41:1 gear reduction 1.9HP w/ Push Button Start
• MSD Pro Billet Distributor
• MSD 6AL Ignition
• MSD Blaster 3 Coil
• MSD Adjustable Timing Control
• MSD 8.5mm Super Conductor Plug Wires
• Hedman Headers 1 3/4" Primaries to 2 1/2" Pipes w/ Flowmaster Mufflers

 

The only time I've EVER heard of something like this is when a friend of mine built a new engine for his Mustang and tightened down his rocker arms waaaaaay to tight on a couple of cylinders. He therefore was not getting full compression (only on those cylinders) as the exhaust valve stayed slightly open all the way around teh 4 strokes. When the cylinders without compression finally did fire off a totally flooded cylinder, there was a big bang about every 10 seconds or so. He thought "zero lash" meant crank 'em down...

 

well before starting it it's taking a lot of mashing on the pedal (which is a ton of gas being poured down there from the double pumper) to get it to crank up. i feel like it's getting so much gas in there it's, like you said... fireing off a flooded cylinder. but it could run fine for a little while then i will idle it up some to say 2k rpms and it will backfire. but i'm understating these backfires they sound more like bombs going off. a ball of smoke blows out as well. i don't get it because it use to run PERFECT and nothing has been tampered with for it to start doing this. i did have to change the plugs to some champion race plugs because the previous ones were fouled. when i changed them out it only took one push of the starter to crank it. someone said the timing was off but like i said nothing has been messed with. everything on the dist. is on tight. however i do have a msd adjustable timing control **** inside the cab that's always been set on 7 and goes to 10. it's been played with a little but it always goes back to 7 when i'm done. although i never heard a difference in the motor before while turning the ****.

 

it was definately a timing problem. i advanced the dist. a few degrees and tweaked the air/fuel adjustments and she lined right out. now it runs the way it did before. one of my buddy's (who has a 10 sec monte carlo) suggested i reduce the jet size on the carb though. it still has a little smoke out of the exhaust and has always done that. i know that 750 double pumper is dumping some juice so i might jet it down and see what it does then.