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Dire need of help!

Grand prix kid 1980

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Okay so i posted a thread last month about my 1980 grand prix lj with the 265 4.3 it wouldnt start and i replaced the ignition coil plugs coil rotor button and cap only thing i havent replaced is the plug wires. I got the no start issue fixed. Fires right up now..Needless to say Ive replaced the carburator and i cut the exhaust short and put a big cherry bomb on it. Ive got a little exhaust leak on it.. But what im getting at is.. Everytime i give it gas and it drops idle it pops out of the exhaust.. I dont think anything is wrong with the valvetrain since i dont drive it im working on it and when i got the car it never use to do this.. Its everytime i go to give it gas it loads up and pops out of the exhaust,shooting flames and all. I have no idea what it could be.. Ive advance the timing and it still does it.. My plugs are gapped at 45° and it says that it should be gapped at 60° idk if maybe that is a cause.. I was also thinking the air fuel mixture on the new carb is messed up. Could the cam idle screw need adjusted.. Do i have a weak fuel pump? Im stumped and i dont know what else it could be.. Any suggestions? Thank you!
 

melsg5

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The gap is supposed to be .060 R45TSX plugs.
The timing is supposed to be 10 degrees BTDC with vacuum to distributor disconnected.
You replaced the carburetor with another stock carburetor?
Are the idle mixture screws accessible and if so did you adjust them?
Did you recheck whether you installed the spark plug wires in the correct sequence?
 

Grand prix kid 1980

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Its an aftermarket replacement. Its a rally brand. As far as i know its stock. Idk if it the jet is bigger on this or not. Will look into that. They are accessible, i think there a little socket-fit like 1/4 in to adjust, not screws. I dislike this since the socket needs to be very thin in diameter to fit inside the hole. I havent messed with it at all. Do you know where it should be at ? Should it be fully screwed in then full screw and a half loosened? I havent rechecked to see if spark plugs are correct sequence. Im pretty sure they are but could be getting wrong info online. Do you know the sequence by chance? Thanks in advance! I was wondering if i could be getting crossfire from the wires. I think i have a few of them hitting each other. I need to put them on the plug wire separators. Appreciate all the info!
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melsg5

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The firing order is 18436572 in a counterclockwise direction.
The idle speed screw is set for 700 rpm in drive.
The mixture screws are adjusted using a tachometer or vacuum gauge. The screws are turned in a clockwise direction a 1/4 turn at a time watching the engine speed or vacuum reading till a drop is noticed and then backing out a 1/4 turn.
My suspicion is you have the plug wire sequence off on two cylinders when you attached them to the distributor cap.
 

Grand prix kid 1980

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Okay so i had no luck today or the past couple days. It fires right up but when i give it just a little gas it backfires out of the exhaust. I give it a little more gas and let off and it bangs real loud. Adjusted timing and mixture screws didnt seem to help any. The mixture screw is a hex and i had to shave down a small socket in diameter to fix it in the hole so i didnt play around to much with it. I dont know why it pops.. It never use too..appreciate all the help
 

Grand prix kid 1980

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Im pretty sure it started doing this after i cut my exhaust off short to throw on cherry bomb but my flexpipe has a nice leak still so im thinking its sucking in air and developing a bang in the exhaust.. Im probably going to take my cherry bomb off and either put a muffler on it or reconnect the stock exhaust out of the back.
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Grand prix kid 1980

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Bad cam or lifter, sticking valve or intake leak?

Doug in P.R. 😎
I don't think its that.. I mean i dont drive the car and its never done that up until i cut the exhaust off.. Im trying to avoid it being that because i just think its the last option it could be. Its definitely a little rich running as well.. Took plugs out regapped to about 55 since it says 60. There all black. Carboned up. Might run a can of seafoam thru it as well. Motor has around 67000 miles and i dont drive it. I think echaust could be sucking in oxygen since i Dont have right backpressure. Reversing it..i put a piece of flexpipe from exhaust to the stock running out the back temporarily and it didnt pop. Idk why it pops ive always done this to cars but im just gonna take cherry bomb off since my flexpipe i got was way to big they was out of the correct size and developed a nice leak... So ill try that tomorrow
 

Grand prix kid 1980

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I dont think my carb has an electrical connector on it. Ive never unhooked it since i took off carb and put new one on. And see that was another thing i was thinking is an o2 sensor is plugged up but i cant seem to find it if it does have one.
 

Grand prix kid 1980

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Ive got a video of whats going on with my car but i dont know how to upload to.. Can i send it to someone who can help?
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melsg5

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did you try the attach files tab on the bottom of the reply box?
exactly what spark plugs did you install, make and number?
when you set the timing, you connected the timing light to the front cylinder on the drivers side?
 

Grand prix kid 1980

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The car fires right up. Sometimes i have to open the choke flap. I have ngk UR 45 in it. I didnt set the timing because it fires right up doesnt seem to be out of time. But when i give it gas its smooth and then when it comes down off the rev it pops and bangs the more i give it the more it gives me.
 
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