69 camaro 350 cid, Holley 4160. Recently changed secondary vacuume spring from black (factory) to purple.... Yellow produced slight bog. Noticable increase in power and gas consumption. Holley specs suggest primaries are .69 w/ secondaries are 134 -39 ????. Noticed that other holley 600cfm had primary jets as low as .63. Would like to tune air/ fuel mixture to produce optimal power and mileage ( although if they conflict, will opt. for performance) THe question is ; how difficult is it to change the primary jets? Do you have to remove the carbeurator? What size range should I begin with or how low should i start. Plan to assess the performance by plug inspection and 1/4 mile speed....not time.
350cid, 3speed manual trans, 3:55 rear posi.
suggestions and experiences appreiciated.