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

  1. #31
    Registered User 87_355_Blazer's Avatar
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    I wasn't able to hook up a vacuum gauge and actually drive around with it, but revving the motor with the vacuum gauge on it when it was parked gave me normal results... vacuum went up with engine rpm, down as rpm fell...

    -- Brad

  2. #32
    Registered User 87_355_Blazer's Avatar
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    Ok, something is bugging me here. Does anyone have a link, or some insight into how I could figure out the master cylinder bore sizes offered on S10s through the years, and over different engine options?

    There has to be some differences here. I know that some guys are using S10 MCs for conversions to other older cars, and I've read enough conversion threads on S10 forums where guys have said they used the stock MC/prop valve and everything was cool... there must be some differences.

    Also, what the heck do the brake codes mean? Mine is a JM5, for 87 at least.. there was also a JM7 option. What is the difference?

  3. #33
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    Try checking vacume at the hose that goes in to the booster. mabey you have colapsed hose.

    just throwing out ideas.
    check out my rides at www.streetsourcemag.com/Profile.aspx?profileid=18534

  4. #34
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    sorry i cant help you with the bore sizes...but i d check for kinked brake lines and rubber lines...you may have old rubber lines that are expanding and affecting ur braking power

  5. #35
    Senior Member billp's Avatar
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    THERE IS A STICKER ON THE BOOSTER, ST, SU ETC, TAKE THAT AND CALL A PARTS HOUSE AND THE WILL BE ABLE TO TELL YOU.
    84 xCab S-15. No longer ugly but still quick

  6. #36
    Registered User 87_355_Blazer's Avatar
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    Originally posted by junk runner jr
    Try checking vacume at the hose that goes in to the booster. mabey you have colapsed hose.

    just throwing out ideas.
    Good idea, but the vacuum measurement I took was right before the check valve.

  7. #37
    Registered User 87_355_Blazer's Avatar
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    Originally posted by cpbaur
    sorry i cant help you with the bore sizes...but i d check for kinked brake lines and rubber lines...you may have old rubber lines that are expanding and affecting ur braking power
    Already checked... I just replaced the hard lines and the flex lines up front about 4 months ago during yet another episode of brake problems. Thanks anyways...

  8. #38
    Registered User stretch59's Avatar
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    Originally posted by billp
    THERE IS A STICKER ON THE BOOSTER, ST, SU ETC, TAKE THAT AND CALL A PARTS HOUSE AND THE WILL BE ABLE TO TELL YOU.
    If you started with a 4 cyl. The booster will not work very well. The "ST" booster from a 4.3 truck will provide better pedal feel. I picked one up last week at the U-Pull-It a couple of weeks ago for $7.50. I'm a couple of weeks from running but JTR publishing says it the one to use. That's not too bad of a price for experimenting. If you can get it with the matching master cyl then all the better.

    If you want to know the bore sizes, go to NAPA Auto Parts. The Balkamp brake catalog lists most bores for any vehicle.

  9. #39
    Registered User Yenko's Avatar
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    Original booster stamped ZT,production option JM7=2.5
    Original booster stamped YC,production option JM5=2.8
    Original booster stamped ST,production option JM3=4.3
    ISRA# 18696

    CMA

  10. #40
    Registered User 87_355_Blazer's Avatar
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    Any idea if the "ST" booster will fit with tall valve covers? I've been cautioned that it "might not"...

    Still no luck with these brakes. I'm gonna grab an electric vacuum pump from the junkyard this weekend and see what that does for the situation. Running out of ideas fast here.

    -- Brad

  11. #41
    Registered User Yenko's Avatar
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    You might try a vacuum canister to help with the vacuum for the booster. That is what I did and it helped allot. I don't need it now cause I got a stock 300 hp motor in there now. Before, when I had a 286dur with .568 lift cam, I needed that canister. I guess I need to take it off(will one of these days). By the way, my booster is for a 2.5. You can see the canister on the driverside fender well in the pictures.
    http://community.webshots.com/photo/...74857344BiKWaB

    http://community.webshots.com/photo/...74857609FXDtfR
    ISRA# 18696

    CMA

  12. #42
    Registered User Yenko's Avatar
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    Originally posted by 87_355_Blazer
    Any idea if the "ST" booster will fit with tall valve covers? I've been cautioned that it "might not"...

    Still no luck with these brakes. I'm gonna grab an electric vacuum pump from the junkyard this weekend and see what that does for the situation. Running out of ideas fast here.

    -- Brad
    I can't tell you if it will or not. I did have tall valve covers and it was close to the 2.5 booster. My conversion mounts are the JTR stealth mounts. I'd say, go to your local parts store and measure the 4.3 booster and compare the sizes. That is about the only advice I could give you.

    On a side note......I love your Chevy II. Were are you at on it? Sorry, this is off topic.

  13. #43
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    I have the ST booster and tall Moroso covers. I had to ding the booster tabs a little with a hammer to get the valve cover to sit down, but I am still able to use studs instead of bolts to mount the valve covers.

  14. #44
    Registered User 87_355_Blazer's Avatar
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    Hmm... I may have to try returning the new booster and see about an ST unit. At this point, I'm just gonna wait until I can get to a junkyard on sunday so I can do some measuring and figuring.

    -- Brad

  15. #45
    Registered User 87_355_Blazer's Avatar
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    Originally posted by Yenko

    On a side note......I love your Chevy II. Were are you at on it? Sorry, this is off topic.
    That's not offtopic at all man. See, that's really the project vehicle there. If I can ever get the Blazer sorted out, then maybe I can get back on the Nova :)

    Here: Nova Site

    Not very far along at this point...

    -- Brad

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