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RE: 390 gt manifold and 428cj manifold By Tim Johnson - 09/04/2002 4:01:22 PM; IP 216.222.116.175 The GT390 intake, first used in 1966, has slightly higher runners than the stock 4bbl intake. They are identified by a large "S" cast into the #1 runner. Place an "S" code intake next to a standard 4bbl intake and you'll see the difference. Use of the "S" code GT intake and the same cam as was later used in the 428CJ moved the peak torque up from the standard 390 4bbl engine rating @ 2800 rpm to 3200. It also added 15 hp to the advertised rating over the standard 390 4bbl. The 428CJ intake has bigger runners and the barrel holes are bigger than the GT's. The CJ parts were designed for mid to high rpm performance whereas the GT components were developed to give the 390 a little more street "umph". The GT intake was desgined to be used with a 600 cfm carb while the CJ was designed to be used with the 730 cfm CJ carb. I'm writing this of the top of my head so forgive me if my painpill soaked brain has gotten some wires crossed! TJ

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Skip Navigation Links.  390 gt manifold and 428cj manifold -- curt, 09/02/2002  428 CJ is basically cast iron hi rise manifold.... -- hawkrod, 09/02/2002 RE: 390 gt manifold and 428cj manifold -- Tim Johnson, 09/04/2002  RE: 390 gt manifold and 428cj manifold -- mike, 09/04/2002  the S intake is not special, it is the same as.... -- hawkrod, 09/04/2002

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