Vacuum problem
Thread Starter
Instructor
Joined: Mar 2003
Posts: 229
Likes: 0
From: Knoxville/Wooster TN/OH
Vacuum problem
Hey guys,
I just bought a 79 vette with a 454 under the hood. While I am happy at he amount of power that she gets to the wheels I was wondering if there was a way to increase the vacuum to the headlights without changing out the cam. I am not sure on the exact duration and lift on the cam that is in the 454 right now but I am guessing about 290+ duration on both in and out with probably about .850 lift. Thanks.
I just bought a 79 vette with a 454 under the hood. While I am happy at he amount of power that she gets to the wheels I was wondering if there was a way to increase the vacuum to the headlights without changing out the cam. I am not sure on the exact duration and lift on the cam that is in the 454 right now but I am guessing about 290+ duration on both in and out with probably about .850 lift. Thanks.
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
Re: Vacuum problem
Well, you could buy an electric vacuum pump. You already have a vacuum reserve tank to operate the headlights so adding an aftermarket tank isn't going to help at all.
I don't know how you manage to drive that car on the street with only 5" of hg. You must have some pretty steep gears. My Fairlane draws 11" and the vacuum system on that is marginal at best. Pulling a 3.89 gear in that and the bottom is still pretty soft...for the first 20 feet.
I don't know how you manage to drive that car on the street with only 5" of hg. You must have some pretty steep gears. My Fairlane draws 11" and the vacuum system on that is marginal at best. Pulling a 3.89 gear in that and the bottom is still pretty soft...for the first 20 feet.
Thread Starter
Instructor
Joined: Mar 2003
Posts: 229
Likes: 0
From: Knoxville/Wooster TN/OH
Re: Vacuum problem (gerry72)
yeah my gear ratio is 3.73 and it doesn't waist any time leaving the mark.
If I where to buy an electric vacuum pump where would I hook it up on the engine?
If I where to buy an electric vacuum pump where would I hook it up on the engine?
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
Re: Vacuum problem (dudeskie)
yeah my gear ratio is 3.73 and it doesn't waist any time leaving the mark.
If I where to buy an electric vacuum pump where would I hook it up on the engine?
If I where to buy an electric vacuum pump where would I hook it up on the engine?
Some of the OEMs also used electric pumps. Cadiallac, Buick, Old, and I think Lincoln.
[Modified by gerry72, 2:21 PM 3/5/2003]
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Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
Re: Vacuum problem (dudeskie)
You're confused about something. This pump does not create engine vacuum. It creates vacuum independent of the engine so that when you're overcammed and can't run vacuum accessories like power brakes, HVAC system and, in C3s, the headlight and wiper door (68-72 this pump will generate the vacuum that will allow these accessories to run.
It is not hooked up anywhere to the engine and has nothing at all to do with the engine. The only way you're going to get engine vacuum up is to increase idle speed, advance ignition timing, raise compression, or put a cam with wider lobe separation angle and less duration.
It is not hooked up anywhere to the engine and has nothing at all to do with the engine. The only way you're going to get engine vacuum up is to increase idle speed, advance ignition timing, raise compression, or put a cam with wider lobe separation angle and less duration.
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
Re: Vacuum problem (Hydratech Braking)
Hmmmm - also sounds like a fantastic candidate for a hydraulic brake assist system... :yesnod:
By the way...fantastic system. Thinking about the conversion of my manual brake system.