Chevelle Brake Vacuum Source - Chevelle Tech
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post #1 of 10 (permalink) Old Jul 1st, 18, 5:42 PM Thread Starter
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Chevelle Brake Vacuum Source

I posted this question In the engine section with no luck so I am trying here . Changing from a Holley to stock original Quadrajet Intake setup on my 1971 Chevelle 454 LS5 MT w/ a/c and Ca. Emissions . I need to know where the vacuum source for the brake booster goes to . Im thinking maybe a steel line coming off the carb base or possibly the Intake fitting , and also was the fitting a 2 separate port for the cowl hood and vacuum storage tank ? Any Input would be appreciated , picture would be great .
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post #2 of 10 (permalink) Old Jul 1st, 18, 6:25 PM
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Re: Chevelle Brake Vacuum Source

Look for a vacuum source behind the carb, below the throttle plates.

If you lend someone $20, and never see that person again, it was probably worth it.
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post #3 of 10 (permalink) Old Jul 1st, 18, 7:00 PM
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Re: Chevelle Brake Vacuum Source

Quote:
Originally Posted by byf41 View Post
I posted this question In the engine section with no luck so I am trying here . Changing from a Holley to stock original Quadrajet Intake setup on my 1971 Chevelle 454 LS5 MT w/ a/c and Ca. Emissions . I need to know where the vacuum source for the brake booster goes to . Im thinking maybe a steel line coming off the carb base or possibly the Intake fitting , and also was the fitting a 2 separate port for the cowl hood and vacuum storage tank ? Any Input would be appreciated , picture would be great .
From the factory, it goes in the boss on intake port #8 that is pointing vertically straight up. 3-port fitting required.
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post #4 of 10 (permalink) Old Jul 1st, 18, 8:36 PM
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Re: Chevelle Brake Vacuum Source

Most Quadrajets have a 1/4 inch pipe tapped hole in the rear of the carb at the bottom location. That is the vacuum source for power brakes. Some have the boss that is not tapped.
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post #5 of 10 (permalink) Old Jul 1st, 18, 9:14 PM Thread Starter
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Re: Chevelle Brake Vacuum Source

Near as I can tell the vacuum came off the rear of the carb base for the brake booster on 1971 BB , but Im still not certain which Is why Im asking . A couple of aftermarket suppliers offer this line for "all 71-72 BB" engines which appears to source from the carb base . Ive also seen the steel line come off the manifold vacuum fitting but Im thinking this was on a 1970 BB . Anyone have a virgin 1971 LS5 MT that could settle this please ?
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post #6 of 10 (permalink) Old Jul 1st, 18, 9:17 PM Thread Starter
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Re: Chevelle Brake Vacuum Source

71-72 All BB
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post #7 of 10 (permalink) Old Jul 2nd, 18, 5:30 AM
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Re: Chevelle Brake Vacuum Source

Anywhere below the throttle blades is ok. Carb base, the plenum, or an intake runner.
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post #8 of 10 (permalink) Old Jul 2nd, 18, 3:42 PM Thread Starter
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Re: Chevelle Brake Vacuum Source

Im wanting to restore It to original , not just what will work . Heres another aftermarket booster line listed for 70-72 BB which appears to connect to the manifold vacuum fitting . This Is why Im confused here .
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post #9 of 10 (permalink) Old Jul 2nd, 18, 3:46 PM
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Re: Chevelle Brake Vacuum Source

Quote:
Originally Posted by byf41 View Post
Im wanting to restore It to original , not just what will work . Heres another aftermarket booster line listed for 70-72 BB which appears to connect to the manifold vacuum fitting . This Is why Im confused here .
3/8 line to booster attaches to this fitting. 2 smaller 1/4 ports for AC & Cowl Hood. Not sure on CA emissions. There is a fitting with three 1/4 ports. All are on eBay.
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post #10 of 10 (permalink) Old Jul 2nd, 18, 7:48 PM
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Over there.
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