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#1
11-30-2024, 10:26 PM
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Rear vacuum port size for Qjet
I am putting a '77 Pontiac Qjet on a '68 GP. The casting number is 17057262. I need to find a vacuum fitting that screws into the baseplate (for the power brake booster, hideaway headlights, etc). The fitting I ordered is too small. Does anyone know what size fitting works? I see some on ebay but they are expensive. I'm hoping I can find something else that will work.
Thanks in advance!
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#2
11-30-2024, 11:01 PM
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I am fairly certain the base plate hole you are referring to is 1/8"-27 NPT. Ames sells that fitting with several configurations containing branches for other vacuum accessories that may need manifold vacuum from that location. HVAC feed to the dash control and vacuum advance come to mind.
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#3
11-30-2024, 11:34 PM
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Confirm, yes it’s 1/8” pipe.
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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! |
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#4
11-30-2024, 11:55 PM
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Some of the baseplate vacuum fittings are 1/4 NPT as well as 1/8 NPT:
https://forums.maxperformanceinc.com...d.php?t=866614
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1964 Tempest Coupe LS3/4L70E/3.42 1964 Le Mans Convertible 421 HO/TH350/3.08 2002 WS6 Convertible LS1/4L60E/3.23 1966 VW Type 2 Single Cab Pickup 140hp 2276 1956 VW Type 2 Panel Van 36hp 1200 1957 VW Type 1 Beetle 180hp 2276 |
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#5
12-01-2024, 04:32 AM
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This particular carb, and all 1975-79 Pontiac M4M Quadrajets, has 1/4" NPS threads for a 1/4" NPT fitting.
1974 and earlier Pontiac 4M Quadrajets has 1/8" NPS threads for 1/8" NPT fittings. FWIW |
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#6
12-01-2024, 11:04 AM
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You guys are all awesome! Thanks for the replies. I am looking forward to getting a QJet back on this car. The PO had a Holley on there. The next step is to address the ignition "upgrades".
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