Do I need a Vacuum Can?

Discussion in 'Engine Topic' started by 04silvyhotrod, Jun 11, 2015.

  1. 04silvyhotrod

    04silvyhotrod Veteran Member

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    I had a stock 350 in my camaro last summer and the brakes worked good on the car. But I built a 327 to replace the 350 and now my brakes are a little stiff. But the car sat for almost a year without being drove. I dont know if my master cylinder is going bad or my cam aint pulling enough vacuum for power brakes. Here's the cam specs.

    Product Line: Lunati Bracket Master II Cam and Lifter Kits
    Summit Racing Part Number: LUN-10120410LK
    UPC: 090127707241
    Cam Style: Hydraulic flat tappet

    Basic Operating RPM Range: 2,000-6,000
    Intake Duration at 050 inch Lift: 230
    Exhaust Duration at 050 inch Lift: 230
    Duration at 050 inch Lift: 230 int./230 exh.
    Advertised Intake Duration: 292
    Advertised Exhaust Duration: 292
    Advertised Duration: 292 int./292 exh.
    Intake Valve Lift with Factory Rocker Arm Ratio: 0.480 in.
    Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.480 in.
    Valve Lift with Factory Rocker Arm Ratio: 0.480 int./0.480 exh.
    Lobe Separation (degrees): 109
    Computer-Controlled Compatible: No
    Lifters Included: Yes
    Lifter Style: Hydraulic flat tappet
     
  2. ssenay72

    ssenay72 Veteran Member

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    Put a vacuum gauge on it, that's the real way to truly tell how much vacuum you have. And how much does your booster require to operate. I ran vacuum cans even if I didn't truly need it. Why not right cant hurt. Ive since switch to a vacuum pump.
     
  3. Damon

    Damon Veteran Member

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    That might be a little iffy for power brakes in a stock-ish 350. Like was said above, check your manifold vacuum at idle. If you're down in single digit vacuum levels at curb idle in gear, that's a little low. Sometimes you can crutch it a little by adding some extra advance in the lower RPMs.
     
  4. 450bench

    450bench Veteran Member

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    I've run that cam with zero problems braking with power brakes and no can. It's just not big enough to warrant a vacuum can with a stock brake booster.
     
  5. hhott71

    hhott71 R.I.P 11/19/18 Lifetime Gold Member

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    That cam is a bit too big for a 327. A 350, 383, 400 would have been a better choice for the displacement.
    Changing to a cam with 220* dur or less would help.
    The old 327/350hp L-&) with the 151 cam was .447" and 221* with 11:1 comp.

    More compression (11 to 12:1) would build more vacuum but 93+ octane would be needed.
     
  6. 04silvyhotrod

    04silvyhotrod Veteran Member

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    Don't wanna change to another cam, runs to good. Guess I'll check the booster. I have 10:5.1 right now with worked 461x heads.
     
  7. lumpy12

    lumpy12 Veteran Member Lifetime Gold Member

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    You say your brakes "are a little stiff". That doesn't sound like a low vacuum symptom to me.
     
  8. camarolife78

    camarolife78 Veteran Member

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    Yea...I had that EXACT cam in my 350 and it only pulled 6 - 7 in of vacuum....Loved the way it ran and sounded! Ran a very large vacuum can to help which it did, but was never perfect. Ended up decamming with the most recent motor and upgrading to roller.

    If you like the cam that much, other option is to convert to hydroboost. There are some people using old astro van parts to do it on the cheap. Some choose to do the more expensive but nicer looking aftermarket performance setup too.
     
  9. 450bench

    450bench Veteran Member

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    I don't get it. I have run that cam before and it ran fine with factory power brakes. It's just not that big of a cam. It made at least 12 inches of vacuum.
    I run the old crane 302 ho6 in a motor currently, which is pretty rowdy, without a can with no issues.
    Interesting.
     
  10. WebbGM

    WebbGM Veteran Member

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    repair

    He's got other issues not the cam pull a vacuum with a AC vacuum pump and try it the check valve at the booster should hold for one or two pumps and see how the brakes act...!
     

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