Car was running 10.20's. Replaced aggresive solid flat tappet cam with aggresive solid roller...No gains...Improved D-port heads throughout lift range with over 20cfm gain at higher lifts...No gains...Replaced 1 3/4 headers and non-mandrel bent 'X' pipe system with 1 7/8 headers and straight 3" pipe...No gains... Can change jet sizes 10 numbers with no change in ET. Converter slippage under 6%. Traction and 60fts great. Is it possible that a Victor intake for 4500 carb is restrictive on a set of 280cfm D-ports?? THe plenum has a little work, but runners are as cast. Don't know where else to look
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1971 Base Firebird..505ci IA 2A Round port E-heads by Butler 348 cfm.. Comp street SR 266/
[email protected] Victor intake/Quick Fuel Q950. 1 7/8" Dougs headers..3" mandrel bent exhaust with Hooker Max Flow mufflers, T-350 well built with 10" 4000 stall nitrous Continental converter..3.73 posi . Caltracs and 10" slicks. Belt driven water pump, alternator, Pwr steering and brakes,Flex fan. 11:1compression, straight 93 octane pump fuel. 10.35 @ 129.88 with 1.45 60ft N/A at 3700lbs race weight.