Vac-advance source question / pondering
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From: North of Toronto - Ontario
Vac-advance source question / pondering
My carb only has a single spot for pulling manifold vacuum and it's used for the evap stuff so I "Tee" the vacuum advance into that line rather than the ported it was using originally
As I was cleaning up some more lines and wires around the motor and I'm looking at the blocked out brake booster port at the back of my carb (I have hydroboost so it's not in use so I connected my new vacuum gauge to there) and I started wondering if all of the non-ported vacuum is the same (in theory I would think they would be) or is there a difference (reaction speed or something) is there any reason I couldn't put a tee-fitting into that rear port and run the vac advance off it instead of the front tee-fitting?
Just a thought as I wait for the rains to stop again
M
As I was cleaning up some more lines and wires around the motor and I'm looking at the blocked out brake booster port at the back of my carb (I have hydroboost so it's not in use so I connected my new vacuum gauge to there) and I started wondering if all of the non-ported vacuum is the same (in theory I would think they would be) or is there a difference (reaction speed or something) is there any reason I couldn't put a tee-fitting into that rear port and run the vac advance off it instead of the front tee-fitting?
Just a thought as I wait for the rains to stop again
M
Had a 1976 L-82, 4-sp
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Vacuum is the same and any change in vacuum is near instantaneous throughout any vacuum hoses. I only use two manifold vacuum ports - one on the back of the Holley for the power brake booster and the other is tapped into the intake manifold directly below the the brake booster port and supplies vacuum to my MAF sensor and the remainder of the cars vacuum needs.
Team Owner
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From: Crossville TN
It is best that you keep the power brake booster supply line only dedicated to that booster. Why? Basically, it comes down to 'safety' issues: if something else it "T";d into the same line and that system loses vacuum, it could limit or eliminate vacuum supply to the booster, also. Not good. Then, too, you don't want to contaminate the booster with anything that would cause deterioration of diaphragm inside, etc. If you tie the vacuum modulator (for auto trans) into the booster line and the diaphragm on the modulator fails, vacuum sucks up tranny fluid which could go into the intake charge [via the carb base] and could also get sucked or transferred into the booster line. That is just one scenario. GM considered all of them...and maintained a dedicated vacuum line for the booster. It's just a good idea. You can T other vacuum system lines together without risking a brake system snafu...
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BUT, he already said he has hydroboost . No reason at all not to run your distributor vac can off of that port and tidy things up a bit.
Team Owner
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From: Crossville TN
Oops! Missed the part about hydro-boost. If the rear (booster) outlet is not being used, it can be used as vacuum source for other systems.
Thanks for the 'heads up' correction..........
Thanks for the 'heads up' correction..........
