PCV causing problems??

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340Duster247

340Duster247

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I got my 408 together and once the engine is heated up good and been run for while the engine shakes bad at idle. I've been chasing this problem for a while and noticed when I pull the pcv and plug it, the engine smoothness right out.
It only shakes when the engine seems to be producing blow by or when my temp gets above 190. It's like the engine does not like to breath back in those crank case vapours

My AFR at idle is around 13.5-14.5. Timing at 34 total
Is there anything I can do to eliminate this?

Holley 750 dp
Eddy headed
Eddy airgap
Lunati 60405
Scat flat top stroker
 
I'd try turning out your idle mixture screws...the engine may want a richer idle, based on your AFRs. Any vacuum leaks?
 
Richen it up. If you are plugging the PCV and it improves you are lean and or the float level is low. Or... vacuum leak.
 
Your AFR is a little too lean and the PCV adding air on top of that is making it leaner so it idles rough.
It's not the vapors but the lean condition making it shake, (lean misfiring)

Hook your PCV up as normal and choke the engine a little with your hand and that will prove it to you.

All engines are not the same, but if I go leaner than about 12.5 to one at idle with the PCV hooked up it misses like a mad dog.
12-12.5 to one or so and it idles real nice.

Oops, lots of answers while I was typing. :D
 
I restricted the airflow through the PCV line to reduce the amount of air the valve was allowing through.
 
You could have a PCV valve that is not correct for your engine too....
 
Two weeks ago installed a Mopar performance PCV valve, expensive but worth it. Cleaned up my Idle and smoothed up my normal take off from a stop.
 
Wow thanks a lot guys. No vacum leaks that i know of. I thought it might be a lean issue, I just set my AFR for best vacum reading. I'll ritchen the idle up and see if that helps. Does anyone know what the right pcv valve is. I just went to a autoparts store and got one for a 340 duster. Mine has the ball bearing and is white/translucent.
 
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