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#21
06-23-2026, 04:55 PM
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Lean is a big part of things here with any Q-jet from 1975 and up since factory duel exh set up’s where history and then cats where stuck in to further make things worse!
Motors making a as installed factory 180 to 220 HP did not need much fuel. To get a new 400 Q-jet combo with headers set up I would start with a .073” jet and a 43 rod on the primary side and that should keep the motor fat enough to not overheat and if the total mechanical timing is no more then 34 with 93 in the tank the motor should not ping when running just on the primary’s .
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! Last edited by steve25; 06-23-2026 at 05:11 PM. |
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#22
06-26-2026, 01:17 PM
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I had a gauge from a brand new mighty vac pump that I was using to read manifold vacuum and it had me thinking my engine was messed. Right when i was learning about manifold vacuum needle readings. Loved it. Anyway I'm sure OP is using same gauge as before.
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69 Gto, 390 posi gears,th400 w/jim hand converter/406 pontiac/#64 HEADS/ 10:1 compression/ 190 PSI with/ TRW 160 thou domes / hooker headers 1 7/8, PRW 1.5 rockers, 405 Crower Springs, Holley 750 vac with proform upgrade, Performer RPM on points / 284 H Single Pattern Crane |
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#23
06-26-2026, 05:22 PM
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My 9.25:1 400 with a 2801 tested 164-170 psi same 400 years earlier with a 280H cam tested 150-156 psi. Keep in mind the 2801 has 53 degrees overlap while the 280H has 60 and a lot more intake duration.
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