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Old 08-15-2014, 11:25 PM
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Default Braking Issue?

Hey guys, I recently got the new engine set-up and noticed the brakes are not as good as they used to be when I had the old Kim Barr Racing 383. Yes, this new engine has a cam with a bigger lift, but the lobe separation is at 112.
Seems the cam is big enough to rob vacuum since it's only pulling 10 inches per square inch where as my old engines pulled around 14-17.
While driving, I apply the pedal and there's a slight hiss of air and then the pedal turns hard which makes it a little harder to stop at speeds around 25mph.

Every time I press the pedal, the rpms rise slightly as if there's a vacuum leak or an indication of a bad brake booster although it was fine before the new engine.
I installed a vacuum reserve canister which seems to have stopped the rise in rpms when the brake is applied, but the pedal is still hard.

Where should I check next? Booster? Air in the line?




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Old 08-16-2014, 04:12 PM
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Beast, I can only give you a GUESS here because I'm in no way qualified to figure out the exact problem. I think it could be the brake booster. Hook up a vacuum pump and see if it can hold a vacuum for a few hours (maybe even over night?). I'm thinking booster more than the cam because you said that there is a slight hissing then the brake pedal gets hard to push.

Doug
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Old 08-16-2014, 04:38 PM
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With the first cam that was in my LT1 I had the so-so brakes and it even stalled on my a couple of times due to low vacuum (the shop did not put in the one I wanted they went more radical). It wasn't until I put a milder cam with 116lsa (if I remember right) that my vacuum came up to around 17lbs and it fixed my problems.
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Old 08-16-2014, 07:34 PM
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Quote:
Originally Posted by oldtinsmith View Post
Beast, I can only give you a GUESS here because I'm in no way qualified to figure out the exact problem. I think it could be the brake booster. Hook up a vacuum pump and see if it can hold a vacuum for a few hours (maybe even over night?). I'm thinking booster more than the cam because you said that there is a slight hissing then the brake pedal gets hard to push.

Doug
I'm thinking it could be the booster since I've never changed it or the master cylinder since I've owned this truck. But then again, I never had a brake issue until the new engine.
The old Kim Barr 383 had a Comp Cams Xtreme 4x4 with a 111 lobe separation with a .500 or so lift.


Quote:
Originally Posted by Poltergeist View Post
With the first cam that was in my LT1 I had the so-so brakes and it even stalled on my a couple of times due to low vacuum (the shop did not put in the one I wanted they went more radical). It wasn't until I put a milder cam with 116lsa (if I remember right) that my vacuum came up to around 17lbs and it fixed my problems.
Did you ever run a vacuum reserve canister?
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Old 08-16-2014, 07:54 PM
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No I didn't. When the first cam was being a PITA to drive the El I replaced it with the current one and have not had a problem since.
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