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Strange idle issue. Slows down and speeds up by itself

1K views 3 replies 4 participants last post by  geeteeohguy 
#1 ·
I'm working on a 66 GTO for a guy. It has a fresh rebuild of 428 Pontiac engine Edelbrock performer intake, Holley 800 spread bore double pumper carb. MSD mechanical advance distributor. It has Comp XE274H Hydraulic flat tapper cam.
It speeds up and slows down by itself. Here is a video of it running. What can cause this condition? I tried blocking the PCV off and it still does it.
Thanks
Danford1

https://vimeo.com/199460492
 
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