Engine surging idle

mercurycapri

Member
May 30, 2006
207
2
18
washington
I have a 82 mustang I just installed the motor and transmission from a 1990 crown vic. Everything is stock except for a long tube headers, dual plane intake manifold and a 2 barrel 500cfm holley carburetor that I took off my truck which has a 390fe motor. My truck ran good with the carburetor but on my mustang its surging at an idle and when I drive it surges. When I start it when it's cold it idles and surges and doesn't changed when warmed up. I took the jets out to check if they were plugged which they weren't. I noticed that the jets are 73 size which I think is a bit large for my engine. Could the big jets be causing my issue?
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
23,434
8,635
203
polk county florida
I think the jets are not causing the surge, check power valve for damage and check for vacuum leaks.
A leaking power brake booster can cause this as well,
A couple questions: was the carb rebuilt and does it act up with the vacuum advance plugged?
 
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