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Old 07-01-2008, 12:48 PM
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save fuel daily driver holley carb

Hi ALL,

I use as a daily driver an 85 trans-am with a carbed 355ci . The engine is about 370 hp ( mostly world products ) and running a 4160 Holley 750 and MSD HEI street fire with 12 degres initial. I've chaged main jets from 70 to 67 and yellow secondary spring instead of silver. Vacuum advance is hooked to ported as manifold was raising my idle to 1500rpm and idle speed screw all the way out could not operate anymore...I'm thinking of putting a little wire in the metering block IFR and or changer discharge nozzle from 031 to 025 and maybe the orange cam to the white one all that to try to save fuel and maybe get more crsip on the throttle.

What do you guys think or have experienced??

Thanks lot.

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Old 07-01-2008, 12:56 PM
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You need to drop down to 600 cfm with 62 jet and long yellow spring along with 45 power valve and use .028 nozzle and with white (218) pump cam.
I had a 73 Chevelle with 355 9:1 CR stock cam advanced 4 with Eldebrock CB3X intake and 375 heads with 600 Holley jetted as posted above got 22 mpg.
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Old 07-01-2008, 01:01 PM
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If timing changes make that much difference, you definitey need a new timing work-up on this engine.
Check out Performance Distributors tech web site for explanation of timing curves and ported vs. manifold vacuum.
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Old 07-01-2008, 01:17 PM
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this engine was built under a combo given by world products " Typical Application Street: 274 Cam: 230/236 .487''/.490'', Dart II Sportsman #955-061010 dual plane intake; 750 cfm carb, 1-3/4'' header. 430HP on 9.8:1 355; 480HP on 383 10.5:1 (varies with displacement and compression ratio)."

I've read that some performance engines liked only ported vacuum and could not handle manifold. Seems like what mine's doing..Fire up perfect cold or hot, idle at 900 rpm and 600 in gear with 9' vacuum.
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Old 07-01-2008, 03:50 PM
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So smaller discharge nozzle and smaller carb cam would not help fuel efficiency? Right now my plugs are perfect light brown. On cruising highway around 2300rpm and hitting a little the throttle the car takes off nice but I can smell gas so would that mean somehow to rich on the pump or nozzle or both ?
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