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#1
02-26-2014, 10:42 PM
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Intake Manifold Question
Question on this stock intake manifold for my 1970 400. This appears to be a vacuum connection but I don't see what would have been connected here. (right next to the "firing order" text)
Seems like it would make a vacuum leak if it were uncovered. Thanks for the help. |
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#2
02-26-2014, 10:47 PM
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Manifold vacuum connection for the vacuum advance. I removed and plugged mine and used the vacuum connection on the carburator.
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1967 GTO, 432 (428+.030), 4-bolt mains, factory Nodular crank, scat rods, icon dished pistons, Lunati HR 243/251@.050, .618/.622 lift, Edelbrock 72cc round port heads, 10.5:1, offy 2-4 intake, Edelbrock 650cfm carbs, Super T10 trans (2.64 first), BOP 10 bolt w/ Eaton posi and 3.36 gears |
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#3
02-26-2014, 10:54 PM
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It's actually the vacuum source for the Thermac unit(s) on the air cleaner.
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#4
02-26-2014, 11:04 PM
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My vacuum advance appears to be connected to this unit cylindrical unit (in front of the spring) on the driver's side of the carb.
@ Rocky. That makes sense. However I don't think those have worked in years. Flaps in snorkels seem to be stuck open. (not sure how to test) If that is the case, should I just plug this off, or just hook up the thermac unit? Thanks for the suggestions. |
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#5
02-26-2014, 11:05 PM
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Just cap it off
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#6
02-26-2014, 11:11 PM
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Thank you
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#7
02-27-2014, 07:04 AM
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Just a note on "capping" off vacuum ports. Seems like the rubber they are making the caps out of gets soft and fails pretty quickly these days. I see this ALL the time with carbs sent here, most of the vacuum caps are rotten.
Even a tiny vacuum leak can cause running issues, and bring in unfiltered air into the engine that can ruin the rings. I've been shoving a small amount of RTV into vacuum fittings that I'm not planning on using, then putting a plastic cap over them in lieu of a rubber one. Most hardware stores have the plastic caps, they are color coded, and hold up to underhood temperatures just fine. I got mine at Lowe's in their hardware section. Sort of related to this topic, I bought a 2012 Harley Davidson Ultra Limited and it developed a light miss and lean stumble around 5000 miles. I bought a tuner for it, but never could tune out the issues in that range. I then decided to purchase a Scream-in Eagle air filter assembly for it, and when I removed the factory air cleaner, found a vacuum fitting at the top of the throttle body with no cap on it. Nice, sucking all sorts of junk into my engine for a few days, glad I discovered it as soon as I did! I mixed up some Marine Tex and filled the vacuum port, and put a plastic cap over it, and the engine now idles nicely and no lean off idle stumble........Cliff
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If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
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