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Thread: Not sure if this is the right forum or not...

  1. #16
    Registered User 87_355_Blazer's Avatar
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    General update: I just got done swapping brake boosters (got a new one). There has been a change, but I'm not sure that it's for the better. I still have the same lackluster performance, but now it seems to vary somewhat. I can't pinpoint an exact trend in it, but generally, the pedal is a lot firmer all the time, rather than before where the first half of the stroke was easy, and then it was like hitting a brick wall. it acts a bit erratic now in terms of pedal feel to be honest, and it really seems to be engine vacuum related. For example... at idle, the pedal is at it's worst, and under decel, after moving along at a decent rpm, seems like it's at it's best.

    I'm about at my wit's end here. I don't like to keep throwing parts at it, and neither does my bank account. I would at least like to get things working on the same level as they were before the swap before I start worrying about making the system "better"...

    -- Brad

  2. #17
    Registered User oldcarguy85's Avatar
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    did u check the check valve? thats all i wanna know?
    1988 s-15 jimmy
    500hp 383
    700r4
    4.10s posi

  3. #18
    Registered User 87_355_Blazer's Avatar
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    New check valve, and tried it both with and without the weird little black canister thing in there.

    -- Brad

  4. #19
    Slow Ride
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    vacuum canister will help.

  5. #20
    Registered User 87_355_Blazer's Avatar
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    vacuum canister will help.
    Wait a sec, aren't you the same guy that told me yesterday you are running the same cam with power brakes, and having no problems? ;)

    -- Brad

  6. #21
    Slow Ride
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    Yes, but a vacuum canister will help you.

  7. #22
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    where are u hooking ur vaccuum hose up to? make sure u have it on a good vac. source and not a part time port

  8. #23
    Registered User 87_355_Blazer's Avatar
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    The port on the back of the holley, down by the base. Same place it was before...

  9. #24
    Registered User oldcarguy85's Avatar
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    what size hose are u using to run that vacum line? as far as i remember, on my blazer we had to sdo somethign wierd becuas the hose size on the brake booster was a bit bigger then that on teh back of the carb. did u clamo the hsoe onto the carb or anything?
    1988 s-15 jimmy
    500hp 383
    700r4
    4.10s posi

  10. #25
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    i would take the carb off and check the vac. port for clogging and clean it...or u might just take the hose off and put ur finger over the port and see how much suction it has...if u have plenty of suction then u know its not vac.

  11. #26
    Registered User 87_355_Blazer's Avatar
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    Originally posted by oldcarguy85
    what size hose are u using to run that vacum line? as far as i remember, on my blazer we had to sdo somethign wierd becuas the hose size on the brake booster was a bit bigger then that on teh back of the carb. did u clamo the hsoe onto the carb or anything?
    If I had to take a guess, I would say 3/8" line.

    I am almost positive it's not clamped at the carb. The setup I am running is like this: short piece of rubber line, hardline, short rubber line (clamped) to black canister (clamped) to rubber line (clamped) to check valve in the booster.

    Same exact setup it had on it before the engine swap.

    I also tried eliminating the weird black canister thing in the line, and went from the hardline mentioned above, and replaced it with one solid piece of rubber line to the check valve. No difference there.

  12. #27
    Registered User 87_355_Blazer's Avatar
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    Originally posted by cpbaur
    i would take the carb off and check the vac. port for clogging and clean it...or u might just take the hose off and put ur finger over the port and see how much suction it has...if u have plenty of suction then u know its not vac.
    Already did one better. Hooked a vacuum gauge to the port on the carb...14-15" of vacuum at idle.

  13. #28
    Administrator Blazin Low's Avatar
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    I dunno, 15" of vacuum is plently...something is wrong somewhere...sorry im no help everybody has already made the same suggestions that I would

    I get 6" of vacuum at idle and my brakes work fine with the stock 4.3L booster.
    this is a test of the sig

  14. #29
    Senior Member billp's Avatar
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    My 274xe has no problems with vacumn except when i do a burnout and hit the brakes as soon as i let of the throttle. If you have an EGR that's bad , that would do it. Look for a vacumn leak, (broken hose, intake leak), Spraying carb cleaner around suspected leak, and listen for an idle change is a good way to find a leak. try the canister.
    Last edited by billp; 10-15-2003 at 08:55 AM.
    84 xCab S-15. No longer ugly but still quick

  15. #30
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    whats ur vac. reading through the rpm range? does it tail off gradually or sharply decline at certain rpms?

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