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Old 09-11-2015, 12:41 PM   #1
cajun chevy
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not enough vacuum for power brake

Only have 11 pounds of vacuum, what to do if I want to install power brakes in my 1972 c10
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Old 09-11-2015, 12:58 PM   #2
engineer_gregh
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Re: not enough vacuum for power brake

I installed a vacuum canister, but I have almost 14 lbs of vacuum. You may need an electric vacuum pump.
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Old 09-11-2015, 04:50 PM   #3
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Re: not enough vacuum for power brake

Hydro boost
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Old 09-11-2015, 05:08 PM   #4
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Re: not enough vacuum for power brake

Why is the vacuum reading so low?
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Old 09-11-2015, 05:12 PM   #5
cajun chevy
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Re: not enough vacuum for power brake

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Originally Posted by Stocker View Post
Why is the vacuum reading so low?
I think the po installed different cams in the little 307, not sure.
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Old 09-11-2015, 05:23 PM   #6
Taibo
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Re: not enough vacuum for power brake

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Originally Posted by cajun chevy View Post
I think the po installed different cams in the little 307, not sure.
Who would bother to change the cam in a 307?
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Old 09-11-2015, 06:00 PM   #7
cajun chevy
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Re: not enough vacuum for power brake

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Who would bother to change the cam in a 307?
All I can see is that when he redid the engine that's what he had on the shelf.
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Old 09-11-2015, 06:07 PM   #8
cajun chevy
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Re: not enough vacuum for power brake

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Originally Posted by cajun chevy View Post
All I can see is that when he redid the engine that's what he had on the shelf.
Checked my notes again, vacuum is 14, not 11, which is still not enough for power brake , I think
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Old 09-11-2015, 06:17 PM   #9
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Re: not enough vacuum for power brake

14 should be plenty but put a vacuum canister on it to have some in reserve. The other option is of course change out the cam it can't run that well if it is that big or put on a hydro boost.
On a side note a cam that is just right for say a 350 is gonna be a little on the small side for a 400 or a bunch on the big size for say a 305 or 307 or 283.
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Old 09-11-2015, 07:36 PM   #10
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Re: not enough vacuum for power brake

I just finished my engine build and had the same concern. I currently am pulling 11-12 in. at idle and my power brakes work fine. Yes there is a little bit of difference from the mild cam I had before, but nothing that I wont get used to. Still stops better than my 06 Tacoma.

I should add that I went from stock power disc/drum to CPP four wheel big brake kit.

Last edited by elkniks; 09-11-2015 at 07:40 PM. Reason: more info
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