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Old 03-23-2013, 06:43 PM
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SBC Vacuum Canister or Pump?

My built 350 SBC has a 300 duration cam, and i would like a little more vacuum for the brakes on the truck.

Would a vacuum canister help? I've also read about vacuum pumps, but I don't know how expensive they are or what all i would need to hook it up.

Thanks guys.

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Old 03-23-2013, 07:17 PM
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Vac can will usually do the trick. I have a customer that makes the ones I use/sell. Looks like two coffee cans with a check valve.
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Old 03-23-2013, 07:58 PM
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Thanks. I was thinking about getting this one, since it comes with the check valves and fittings.
Summit Racing® Vacuum Reservoirs SUM-G1464 - SummitRacing.com
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Old 03-24-2013, 12:22 PM
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vacuum

Van canister works just fine. Used them several times without any problems. Far less expensive then a pump.
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Old 03-24-2013, 02:38 PM
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Would a vacuum canister store more vacuum than the engine makes? If it has 11 inches of vcauum at idle how can it store enough to make power brakes work? Or, am I looking at this wrong?
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Old 03-24-2013, 03:39 PM
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The engine will create more vacuum when it is running at speed under part throttle, and during deceleration, than it does at idle.
The check valves allow you to capture this higher vacuum and then use it for brakes at low speed.
How long it works (volume capacity) depends on the size of the tank.
Correct base idle timing also helps a lot.
Big cams need a lot lot of idle timing. Often locked out timing that allows full timing right at idle is best with big cams.
The vacuum reservoir is not a replacement for this.

With a auto transmission that big Lunati cam with 246deg duration and 108LSA really likes locked out distributor timing.
(no mechanical advance curve)
Needs full timing at idle. This will improve the idle vacuum and the power brakes. As well as the idle quality and thottle response.

Last edited by F-BIRD'88; 03-24-2013 at 03:52 PM.
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Old 03-24-2013, 05:10 PM
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How good would this work at the track? From the pits to line-up, burn out, staging etc? Wouldn't it take a really big tank for all that?
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Old 03-24-2013, 07:30 PM
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Thanks guys. I have a Holley 750 double pumper on the truck, does the canister hook up to the carb or something else?
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Old 03-24-2013, 09:52 PM
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vacuum

carb to canister...canister to brake booster. Easy to hook up and yes, it works great at the track and on the street. your constantly creating more vacuum except at idle...so no problems needing giant canisters.
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Old 03-25-2013, 03:28 AM
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If you keep pumping the brakes you will exhaust the supply of vacuum from the tank.
The added capacity allows a few more brake pumps. If you exhaust the PB's go to neutraland raise the idle speed with your foot off the brake petal. This recharges the canister.

Avoid pumping the brake petal. Same as a trucker does , with air brakes.
or you use up all the air.
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Old 03-25-2013, 07:19 AM
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vacuum

Yes, F-Bird'88 is telling you correctly.
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Old 03-25-2013, 07:33 AM
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I never had any luck with vacuum tanks... The check valve or valves will open with any amount of vaccum..

The only thing that worked for me was to run a piece of steel tubing from the carb base to the booster (with a small amount of hose off the motor for vibration). Remove the vacuum can and adjust the brake pedal ratio to 6 to 1... My brakes work well now with only 9" of vaccum...

I use a 1" bore master cyl...
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