my engine pops out the exhaust when im accelertaing in 2nd gear. its not a loud backfire but more like a gentle pop pop pop sound. it only does this in 2nd gear until i shift in to 3rd gear and the popping sound goes away. what should i check to fix this? thanx

 

Sounds like your timing is off. What are you working on?

 

its a mostly stock 400 with edlebrock carb/intake and hedders. my neighbor brought over his timing gun when i bought the truck 3 months ago. he set the timing i cant remember either 32 or 34 degrees. the truck ran great and still runs good other then the popping sound which didnt start until a few weeks ago

 

You need to set your base timing with the light according to the sticker. Set it yourself so you know where it's at. The fact that "your neighbor took care of it" is not grounds to rule out a timing problem, because that's what your problem smells like. It's a variable you need to clear.

 

there are no stickers on the engine for setting timing but i remember him setting the base timing at 6 degrees. it was the total timing im not certain on either 32 or 34 degrees. i cant ask him cuz hes on the road for 2 weeks. i dont have 40 dollars to buy a timing gun yet but i will when i can. i thought the dizzy may have slipped but it wont budge when i try to turn it and its still lined up with the scratch marks my neighbor made. if my timing chain jumped that would effect every gear right not just 2nd?

 

Timing issues would be my first guess too, if it's not timing.... are you running rich? gassy exhaust? fouled plugs?

You might be dumping raw gas into the exhaust where it then ignites causing the "pop pop pop" sound you hear.

 

i got a timing gun an was able to mess with it today. the base timming is 6 degrees and when i rev the motor it goes up to 32 degrees. is this to high or to low? i still have popping sound.

 

I'm thinking burnt valve. If so you could hold a dollar bill up to the exhaust pipe, if it sucks it in- burnt valve.

 

I had a few mental images of how a noob might do this...

Let's clarify, hold a dollar bill lightly between your two hands about an inch away from the exhaust tip. As the exhaust pulses it should push it away and bow away from the pipe. If drawn in...

Dual exhaust? Test both pipes.

 

i tried the dollar bill trick this morning all it does is blow the dollar out. it doesnt suck in to the exhaust any. any other ideas?

 

First I heard of this...lol but check your cap/wires/plugs for the easy stuff first..carb adjustment..

 

Are you positive it just started a few weeks ago, or maybe you just started noticing it a few weeks ago?

Is your vacuum advance working? where is it connected, carb or manifold?

 

honestly i dont know when it started but i started hearing it a few weeks ago. how do i check the vaccum advance? the tube from the dizzy connects to my intake. thanx for the help so far

 

Alright we need some more info to help. Do you have a tach in your truck? If so is it starting to pop when your higher up in your power band such as about 4-4,500?

Does the truck feel like it's falling on it's face or losing power when it pops? Is this only a second gear issue? Or does it happen when your in 1st to?

Also the vaccum line hooked to the vacuum advance on your distributor should NOT be connected to manifold vaccum. It should be connected to the carb. There should be two vacuum nipples on the edely carb right by the idle mixture screws on the front.
plug it in there. it's a timed vaccum hook up.

If your vaccum advance is truely hooked to the manifold vaccum then I'll bet my underwear that's your problem. It would over advance it causing detination.

 

Pull the hose from the intake, remove cap from dizzy, suck on end of hose and watch for the mechanism inside dizzy to move.

When you reconnect the hose plug it into the passenger side port on your carb (remember to plug the open port on the intake).

After changing vacuum sources (ports) you'll probably want/need to bump up your base timing (to 10-12 degrees) and adjust the carbs idle speed.

Agreed!