ive been going through this engine install over the last 3 weeks, and its idle has been great, but it fall on in face upon throttle (more than 20%). missing, backfiring, all sorts of fun.

so i pulled the air cleaner & housing off to inspect the side glass, and i found this little bastard stuck into the hose my middle finger it touching.
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after it was removed (no other changes) it seems like it only idling on one rotor.
if i give it a little bit of gas, it smooths out and goes back to it usual thing around 1300 rpm, (missing and popping) but i have to really play with it to get it above 3k.

this seems to me like its a huge vac leak, or a faulty carb. you guys want a video of what its doing?

any help would be appreciated.

 

also now it will die if idled while cold, and it hasnt done that since i got it running. just replaced the coils, and spark plugs, new cap and rotor, wires were from my old engine, but that ran great besides the low comp in the rear rotor. that one pulled to the redline nicely. i have the carb off that engine and am thinking about taking the afternoon tomorrow to swap them just to see what happens.

 

put that plug back in and it idles fine. weird.

 

so if i am correct, the plug stops the coasting valve from (which is stuck open i guess?) from letting fresh air bypass the carb. which is why it seems its running on one rotor.

 

Time for an emissions delete. Remove everything and cap off all the vacuum ports at the base of the carburetor. Run the second line straight to the leading vacuum advance pot and split it to the orange solenoid, which will the go to the trailing advance pot.

 

You will then need to check your timing and fuel\idle mixture.

 

the shutter valve is bad, someone already plugged the leak.

 

thanks for the replies! im going to try and and play musical carbs (have 2 full, one stripped) tomorrow, after the brake job is complete. also replace that faulty shutter valve, and free up the probably stuck coasting butterfly. if that doesnt help ill be removing the rats nest. and using my stripped nikki, as its already setup for mechanical secondaries.

 

Its a 1980.

 

engine is an 83, unless it has been swapped from the chassis i removed it from.
my chassis is a 79.

 

If for whatever reason it does have a shutter valve, remove it and block it off.JB Weld works good there. If engine vacuum pulls the butterfly closed you basically are running on one rotor. Even better... Swap your 79 manifold onto the engine.

 

motor that was in mine when I received it, was also an 82-83......any reason you recommend removing other than that it restricts the airflow to the 2nd rotor? its supposed to be an anti backfire apparatus if im thinking correctly... just curious.