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  1. #1
    Jr. Apprentice huntxtrm's Avatar
    Join Date
    Nov 2008
    Cleburne, Texas

    Talking 86 suburban vacuum issues, high performance

    Hello to all, I have a 86 1/2 ton suburban 4x4 with a 350 chevy, performer intake, performer carb, performer cam, mallory unilite mechanical advance distributer, rest pretty much stock. 35" ground grabbers, 3.42 gears(soon to change to 4.11). I have vacuum issues due to the performance mods to the engine. What do I have to hook up for this thing to run right. Can someone give me a schematic, or something. all emissions equipment is somewhere else besides under my hood. No airpump, air injectors, egr, ect.... All I want to work is my A/C and Heat, Power brakes, Transmission. Just the nessesities. Thanks for your help.

  2. #2
    Jr. Apprentice huntxtrm's Avatar
    Join Date
    Nov 2008
    Cleburne, Texas


    nobody likes suburbans anymore I guess, DANG!

  3. #3


    Are you missing the under-hood decal with all the vacuum-hose routing? If so, I *think* I can get a scan from my '86 Factory Service manual.

    The brake booster should tie directly into the intake manifold, usually via a fat rubber hose and/or metal tube (about 3/4" diameter). If the hose is in place and you still have poor brake-boost performance, either your booster is defective or your performance cam/carb/etc. is not producing sufficient vacuum.

    If the latter is the case then you'll need to add a 'vacuum reservoir' (an oxymoron, I know). It's little more than a big, empty canister, usually with a one-way valve, that's designed to supplement low-vacuum conditions.

    Summit Racing (for example) sells one for $31:
    Last edited by KirkW; 02-20-2009 at 06:57 PM.
    Norwalk, CT

  4. #4


    Did you change the Cam also?
    Usually a higher lift cam will kill the vacuum.
    Two ways this can be done:
    Add an additional or larger vacuum canister to the engine compartment, or find an Isuzu Diesel truck and use the vacuum pump from it to run these items.
    Isuzu trucks use GM parts and engine accessories, the mounts and belts should be over the counter.
    Some Isuzu trucks running GM 350 engines also run a vacuum pump.

  5. #5
    Jr. Apprentice huntxtrm's Avatar
    Join Date
    Nov 2008
    Cleburne, Texas


    it has a "rv" type cam. Not big on lift or duration, considered mild. Does lope a little, not enought to effect the vacuum. The trouble I am having is, I removed the cruise controll vacuum diaphram, and wiring, no emmisions whatsoever, no smog pump, no egr. Basically all the under hood vacuum has been removed. I am left to hook up the trans selonoid, I think I found it, it is a vacuum operated electric selonoid. I have to hook up the pcv valve, I think hooks to the large vaccum port on the front of the performer carb. The line to my A/C controls, And I did leave the factory vacuum canister on the truck, just in case. What I need to know is how to hook this stuff up, and where and what direction the one way valves need to go to make it work right. I also have issues with certain unidentified, unhooked items under the hood that I would like to remove if possible. Is there any literature that explains the different parts under the hood? I am trying to clean uup under the hood to make it look nice and neat. Thanks to all for your help!

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