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Chris (aka-Moose)
Chris (aka-Moose), Technician
Category: Car
Satisfied Customers: 1044
Experience:  16 years of experience
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354 Hemi in a Willys Pickup 1953 pickup: Just installed a new

Customer Question

Just installed a new Holley Street Avenger 670 on a 354 Hemi. This replaced an Edelbrock. This is supposed to be ready to go, out of the box. Haw. On first run it was running at over 2500 RPM. I started backing out the idle screw. After several attempts & with the idle screw about as far as it may go & with the electric cloak backed down to the stop the engine is still above 1500 RPM. I don't think this is right. What can you suggest ?
Submitted: 1 year ago.
Category: Car
Expert:  Dr. Hamman replied 1 year ago.
Hi, I am a professional certified mechanic, with an engineering background,and 35+ years experience. I will do my best to assist you. Also keep in mind I don't know if you are a pro or a novice, so feel free to add any additional info at any time. I am a Mopar collector, not many 354's left great old engine. The idle speed adjustment screw normally will bring the idle down. You should look at the area on the throttle shaft the idle screw contacts, on the end opposite the screw head. If the screw is backing off and loosing contact with the shaft, either something is mechanically holding the butterfly open. Or the fast idle setup that is actuated when the choke is on has taken over to raise the idle speed. If that is the case adjusting the idle speed on the choke side of the carb should be adjusted. Another thing is make sure the back barrels are shut, and not cracked open. The last thing is a vacuum leak can cause a fast idle, normally the other issues will be the problem. With the engine running you can spray around the suspect areas with a can ofWD40. If you hit a vacuum leak with the WD40 the engine will speed up for a second or two. Go these issues and if you have any more questions at all, I am here to help. Good luck with it, have a great day, and Thanks for using Just Answer. I do not get paid for my work unless you rate at 3 to 5 Smiley Faces o rStars, a bonus is always greatly appreciated. If the answer is not clear, let me know what additional help you need, and I will be happy to assist you further.