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02-24-2013, 06:41 PM
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#1 |
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Registered User
Join Date: May 2012
Location: Eastern, NC
Posts: 429
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Vacuum question
I purchased a 71 C10 last summer. The truck runs great. The PO rebuilt the engine adding a HEI and a bigger carb. I love the truck but did'nt like the manual brakes so I just added power brakes. However, the brakes still feel like manual brakes. After checking my vacuum, my question is what should my vacuum range be for my booster to work properly? I'm getting between 13 to 15 vacuum readings (mostly 13 - 14). Is this enough vacuum for the booster?
I've check and don't see any area's where I may be loosing vacuum. I read somewhere that some modified engines do not put out as much vacuum. What are my options? Is 13-15 vacuum readings good and or should I just add a hydroboost brake system? |
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02-24-2013, 07:14 PM
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#2 |
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Registered User
Join Date: Jun 2010
Location: Upland Ca
Posts: 4,149
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Re: Vacuum question
Tell us a little more about your swap, new parts, used parts? What type of booster/master? Most say 18 inches of vacuum are needed for power brakes, I've got 13-14 at 750 RPM and my power brakes work just fine.
__________________
1972 C10 SWB, Air, PS, PB, 350/350THM. Second owner. 1965 Corvette roadster, 44K miles, 327/365 SHP, 4 speed, side exhaust, knockoffs, teak, second owner (bought in 1970), Have ALL numbers matching components. My frame off restoration thread: http://67-72chevytrucks.com/vboard/s...d.php?t=556703 |
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02-24-2013, 07:17 PM
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#3 |
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Registered User
Join Date: May 2011
Location: Northern Calif.
Posts: 3,794
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Re: Vacuum question
I've got a very steady 17in. and my power brakes work great. Have you checked your vac. with the booster line off and plugged?
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02-24-2013, 07:28 PM
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#4 |
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Registered User
Join Date: May 2012
Location: Eastern, NC
Posts: 429
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Re: Vacuum question
I'm using a new MC and booster power brake conversion kit. And I plugged all the lines and took readings directly from the manifold port.
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02-24-2013, 07:48 PM
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#5 |
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20' Daredevil (Ret)
 
Join Date: May 2003
Location: Jefferson State
Posts: 13,763
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Re: Vacuum question
Is that from the port at the rear of the manifold? And is your vacuum line big enough?
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- Mike - 1972 K20 LWB 350/350/205 RIP El Jay |
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02-24-2013, 08:33 PM
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#6 |
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Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,752
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Re: Vacuum question
Bump your timing up and your vacuum will increase too.
What's your timing at now? |
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02-24-2013, 08:43 PM
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#7 |
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Registered User
Join Date: Dec 2012
Location: Altoona Iowa
Posts: 481
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Re: Vacuum question
You didnt say if you were pulling your booster vac off of the manifold or carb? I came into an issue of vac pressure when using the manifold. Better off using back port of carb....direct pull of vacuum. also make sure all ports are plugged one way or another on the large carb and small leaks will drop your pull.
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02-25-2013, 03:30 PM
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#8 |
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Registered User
Join Date: Jul 2012
Location: White Salmon, WA
Posts: 263
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Re: Vacuum question
I would bleed brakes again. You have enough vacum for booster.
I would continue to use manifold vac outlet for booster and not the carb because that should be your pcv, otherwise you'll either be running crankcase crap into only one cylinder with pcv into the manifold vac (way too lean) or if you T for carb then chance of muck in booster. |
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