Small block idles rough only when in gear

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nitronut

nitronut

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Found it! The cap on the rear intake vacuum port was cracked. Replaced it and fixed the problem. Thank You! I have a mildly built small block 360 which idles very rough when put in gear. (idles smooth in park). Only recent changes to the motor was I adjusted / took out some slack on the throttle cable. Starts quickly when hot and have to crank a few seconds when cold which is normal for the engine. Checked all the carb's vacuum plugs, spark plug wires, etc. Has me totally baffled. Would taking a little slack out of the throttle cable cause this?
 
Last edited:
Put a vacuum gage on it.
Post pictures of your motor setup
 
I bet your A/F is wrong. I battled that for about 3 months and a turn of the screw fixed it. Cant remember if it was rich or lean...make sure the advance plate in the distributor is greased too. Found mine (340 dual point) to be gunked with hard grease limiting its return speed and position. check your timing in gear .
 
You might have moved the throttle blade position slightly when you took out the slack. Since it was the only change done, the effect has to be directly connected.
Also look at the carb itself on the outside to see if you bumped any linkage around.
 
Make sure throttle cable is returning to idle.
I set my timing and idle mixture in gear.
 
69FBCuda said:
Put a vacuum gage on it.
Post pictures of your motor setup
Click to expand...
Found it! Thank you. The vacuum port cap on the rear of the intake was cracked. Put a new one on and fixed it. What a huge relief. Thanks again!
 
fishmens67 said:
Make sure throttle cable is returning to idle.
I set my timing and idle mixture in gear.
Click to expand...
Found it! The cap on the rear vacuum port of the intake was cracked. Put on a new one and fixed it. Thank you!
 
rumblefish360 said:
You might have moved the throttle blade position slightly when you took out the slack. Since it was the only change done, the effect has to be directly connected.
Also look at the carb itself on the outside to see if you bumped any linkage around.
Click to expand...
Found it! A cracked cap on the intake rear vacuum port was cracked. Replaced it and fixed the issue. Thank you!
 
pishta said:
I bet your A/F is wrong. I battled that for about 3 months and a turn of the screw fixed it. Cant remember if it was rich or lean...make sure the advance plate in the distributor is greased too. Found mine (340 dual point) to be gunked with hard grease limiting its return speed and position. check your timing in gear .
Click to expand...
Found it! A cracked cap on the rear intake port was bad. Replaced and all is well. Thank you!
 
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