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Old 10-17-2010, 07:49 PM
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Don't have enough vacuum

I installed an SSBC complete disc brake system on a 69 Firebird recently and now that it is done and running it has a terribly hard pedal, it seems good at times but then back to real hard. From what I can tell it just isn't getting enough vacuum to give it good assist, I stuck a vacuum gauge on the engine (500HP 454)and it shows 0in vacuum at idle and maybe 10in at 3000 RPM. What can I do to make sure we have ample vacuum supply ?
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Old 10-17-2010, 07:52 PM
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Install an auxillury vac pump, summit sells them.
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Old 10-17-2010, 08:05 PM
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We installed a March "Revolver" pulley sytem on this thing so I'm not sure if it will accomodate one but its worth looking into , thanks.
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Old 10-17-2010, 08:15 PM
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They sell one thats electric, if summit racing doesnt have one, check out speedway motors.
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Old 10-21-2010, 09:35 PM
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Do you have a reserve canister with a 1 way valve? 10hg is way low but if it ever gets higher it'll stay in the can. I have 10hg at idle which doesnt hold my brakes but my reserve can gets 18hg after a few revs.
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Old 10-22-2010, 09:20 PM
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I had the same trouble.. I changed my brake pedal to the manual 6:1 ratio with the power booster still in use and I have excellent braking now..
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Old 10-23-2010, 12:45 AM
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i had that problum and changed the canister solved the problum the canister was colapsing just enough to cause problums
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Old 10-23-2010, 07:32 AM
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Quote:
Originally Posted by outlaw17
Iit shows 0in vacuum at idle ?


For real ? that must be one huge cam, blower.

Was this a manual brake car before ?
I can not tell what all you changed, but if you did change the booster there should be a bit of free play in the peddle before the booster is activated. If not it will never build vacuum .

Hard peddle no vac assist period, too check.

Engine off, put foot on brake peddle, with pressure on the peddle just start the, engine if the booster is working the peddle will go down some. That tells you the system, booster is working.

Where are you getting the vac from, carb or manifold? Manifold is best, a carb has what is know as a timed port that does not have a vac signal at idle , a common mistake.


Start there
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Old 10-23-2010, 09:30 AM
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Quote:
Originally Posted by pepi

Where are you getting the vac from, carb or manifold? Manifold is best, a carb has what is know as a timed port that does not have a vac signal at idle , a common mistake.


Start there
THE most common mistake I think. I had the same problem with large overlap cam and installed http://www.rhoadslifters.com/ to fix it.

But of course this shouldn't be even thought of until your vacuum source is verified.

Brian
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Old 10-23-2010, 07:37 PM
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How’s that hopey-changey thing
 
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Quote:
Originally Posted by MARTINSR
THE most common mistake I think. I had the same problem with large overlap cam and installed http://www.rhoadslifters.com/ to fix it.

But of course this shouldn't be even thought of until your vacuum source is verified.

Brian
I get around my low vacuum, 7in @ idle 1000rpm using an electric pump, in use for 10 years very satisfied with the results. I now see that Summit is offering them, they are the place to buy, 50 bucks lower big company lower price all good.

Last edited by pepi; 10-23-2010 at 07:48 PM.
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Old 10-24-2010, 08:47 AM
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