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#1 |
Registered User
Join Date: Jul 2001
Location: Oxnard, CA
Posts: 143
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Brake booster
I am installing power disk brakes on my 69 (front only) and have a few questions: on my intake manifold (250 6 cylinder) there is only one vacuum port and it is being used for the transmission (TH400). Can I use a T fitting for the booster and trans or will I lose enough vacuum to cause problems with both items and if so where can I tap into to get vacuum for the booster? Second Question: I have a manual proportioning value to set bias. People tell that I will need a metering value also, but I have been unable to find any doc that tells me to use a metering value. Anybody out there know about this?
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1969 GMC S/B S/S 3" drop |
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#2 |
Firefighter
Join Date: Feb 2001
Location: Yellville, Ar, USA
Posts: 1,943
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Question # 1.You could do the T fitting or does your carb have a port in it that you could use for the booster? Usually a 3/8" plug I think, at the base of the carb.
Question # 2. I have no idea.
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'72 Chevy SWB 350 Auto '67 GMC LWB 350 4 speed '70 Chevy 4x4 Stepside 350 Auto Yellville, Ar. USA ![]() ![]() |
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#3 |
Registered User
Join Date: Jul 2001
Location: Oxnard, CA
Posts: 143
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B and B the one on the carb is used for my vacuum advance. Thanks, I will try the T
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1969 GMC S/B S/S 3" drop |
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#4 |
Senior Member
Join Date: Apr 2000
Location: Delta,Pa
Posts: 14,950
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that little vaccum part isnt going to pull enough vaccum for the booster and it will not work correctly. you need a 3/8 port thats on its own for the booster otherwise your not going to have any power assist which is very bad with a master cylinder thats made to have power assist
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Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member. |
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#5 |
Registered User
Join Date: Jul 2001
Location: Oxnard, CA
Posts: 143
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cableguy0 So I may have to tap a second hole in my intake man that will take a 3/8 fitting.
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1969 GMC S/B S/S 3" drop |
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#6 |
Registered User
Join Date: Apr 2003
Location: missouri city, tx
Posts: 4,486
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on my 350 4 barrell i already have the hose and everything coming off the bottom of the carb. plate or something?
see the black hose in the front of the pic? thats my vacuum setup for power brakes but i dont have power brakes yet so there is a spark plug -- i didnt do this the po did
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70 longbed 496/th400/Ford 9" |
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#7 |
Registered User
Join Date: Jul 2001
Location: Oxnard, CA
Posts: 143
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Is that your fuel line with the kink in it?
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1969 GMC S/B S/S 3" drop |
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#8 |
Registered User
Join Date: Apr 2003
Location: missouri city, tx
Posts: 4,486
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it used to... it still ran amazingly. i replaced it since i took that pic. and yes it was the fuel line
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70 longbed 496/th400/Ford 9" |
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#9 | |
The Sauz
Join Date: Mar 2002
Location: Chilliwack BC, Canada
Posts: 149
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Quote:
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68 lwb 2wd (spread between 3 garages) 72 Burb - Flat Deck 92 Yukon 3" lift - 33's - the new bush pig 01 Sierra - Daily Driver (for now) |
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#10 |
Registered User
Join Date: Jul 2003
Location: north of Phx AZ about 30 miles
Posts: 698
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Just get the prop valve off a power brake truck. You can either drill and tap a hole in your man or I think they sell carb spacers with a hole and hose barb in them. At least they sell them for 4 barrel applications.
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Andy,Phx AZ '67 C-10 (Ahhh, done at last. Well there is that disk front end I want to put in and...) "23 C-Cab-sold '48 Ford 8N tractor(still working) '67 Scout(Now on the road) '70 MG B.-sold |
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#11 |
Registered User
Join Date: Mar 2003
Location: Lincoln, NE
Posts: 32
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sixty8chev: the master cylinders for these trucks is the same for with or without power brakes but the master cylinder for the 71/72 is different then the one for the 67-70. The one for 71/72 is shorter and wider and for the 67-70 the cap has to round circles on top of the same size. I think both will work but maybe different mounting holes?
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70 Custom-10 LWB |
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#12 |
The Crazy Kracka
Join Date: Dec 2003
Location: San Diego, Ca
Posts: 60
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They make plugs for intakes that are t shaped so that you can run one side for the brake booster and the other for the vaccum modulator for your Tranny
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#13 |
Registered User
![]() Join Date: Sep 2003
Location: DFW
Posts: 765
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look at the vaccum port for the pcv it should be 3/8 tee that one to the booster and in that conversion, the later d/b master would be the one to use if the resivor is combined it wont matter, but if it has seperate ones the larger one is for the disks. the calipers requires much more fluid than the small rear cylinders.
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The problem with America is stupidity. I'm not saying there should be a capital punishment for stupidity, but why don't we just take the safety labels off of everything and let the problem solve itself? |
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#14 |
My other Love
Join Date: Aug 2001
Location: Castlegar B.C. Canada
Posts: 4,085
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i believe there should be a plug on your intak manifold, take the plug out, thread a fitting onto and stick a hose on it
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