brake issues after cam install

Tech discussions on the L77 6.0L V8.
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kevink
Posts: 480
Joined: Sun Aug 09, 2015 12:55 pm

Re: brake issues after cam install

Post by kevink »

I have a much bigger cam compared to the one discussed in this thread and my brakes are fine. I'm not sure what the problem is, but I don't think it's the cam.
2011 9C3: 11.48 @118.
Ridgeppv
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Joined: Wed Oct 20, 2021 4:59 pm
Location: Indianapolis

Re: brake issues after cam install

Post by Ridgeppv »

I am running a stage 2BTR cam 225/238 .620"/.605" 113+3 with stock convertor. Currently had this issue tonight. My vacuum hose on the back of the intake was cracked and replaced it, but will wait till morning to verify this.
2014 6.0L BTR Stage 2 Cam, DOD Delete, 3.45 diff, long tube headers, VCM OTR Intake
bstoner
Posts: 233
Joined: Wed May 05, 2021 2:12 pm

Re: brake issues after cam install

Post by bstoner »

I think the OP issue was a vacuum leak somewhere. He said 8" when he should be getting closer to 18-20". I bet he had a leak.
2014 Caprice PPV, 6.0L, BTR Stage 2 Cam, 3.45, 3" exhaust, Rotofab intake, Chris Henry tuned, future LSA....
Ridgeppv
Posts: 74
Joined: Wed Oct 20, 2021 4:59 pm
Location: Indianapolis

Re: brake issues after cam install

Post by Ridgeppv »

Replaced the rear hose and still doing it but at low RPM. Going to get a vacuum gauge now to test it. Where should I connect the gauge at?
2014 6.0L BTR Stage 2 Cam, DOD Delete, 3.45 diff, long tube headers, VCM OTR Intake
Ridgeppv
Posts: 74
Joined: Wed Oct 20, 2021 4:59 pm
Location: Indianapolis

Re: brake issues after cam install

Post by Ridgeppv »

Vacuum test was 8" so vacuum leak just gotta find it now
2014 6.0L BTR Stage 2 Cam, DOD Delete, 3.45 diff, long tube headers, VCM OTR Intake
Ridgeppv
Posts: 74
Joined: Wed Oct 20, 2021 4:59 pm
Location: Indianapolis

Re: brake issues after cam install

Post by Ridgeppv »

Tested for vacuum leak the old way with carb cleaner and found no varation in idle anywhere. Will perform a smoke test this afternoon. Anyone have any suggestion?
2014 6.0L BTR Stage 2 Cam, DOD Delete, 3.45 diff, long tube headers, VCM OTR Intake
BluesBro
Posts: 134
Joined: Tue Aug 03, 2021 1:26 am

Re: brake issues after cam install

Post by BluesBro »

Haven't had an issue with the L77 yet, but on the older LM7s the intake manifold gaskets would tend to fail on the underside.
2014 Caprice PPV 6.0L - TSP Stage 1 Cam, Solo 3in Mach Cat Back, VCM OTR, Pedders Coilovers, HP Tuned
2002 Avalanche 5.3L - MBRP Exhaust, RC 6in Lift
bstoner
Posts: 233
Joined: Wed May 05, 2021 2:12 pm

Re: brake issues after cam install

Post by bstoner »

Do you have a cam installed? Any possibility the cam was installed a tooth off? Do you have a large cam with a low LSA, a lot of overlap? Do you have the idle set real low? You could pull the #1 spark plug, driver side valve cover, mount a degree wheel on the pulley, and check the cam timing.

Also buy a pack of caps and plug every vacuum port to measure. Possible it could be an internal leak in brake booster, Evap, etc that won't be obvious with an external check. Then it's time to start pulling the intake to check for internal leak.
2014 Caprice PPV, 6.0L, BTR Stage 2 Cam, 3.45, 3" exhaust, Rotofab intake, Chris Henry tuned, future LSA....
Ridgeppv
Posts: 74
Joined: Wed Oct 20, 2021 4:59 pm
Location: Indianapolis

Re: brake issues after cam install

Post by Ridgeppv »

Well double checked the timing and it is good. Did a smoke test on it and did not leak anywhere. Has 20" of vacuum at 900 rpm but needs to be tuned to correct the idle. So if anyone runs into this just wait to get it tuned before you check vacuum. Depending on the cam you install.
2014 6.0L BTR Stage 2 Cam, DOD Delete, 3.45 diff, long tube headers, VCM OTR Intake
CrashTestDummy
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Joined: Sat Feb 07, 2015 2:31 pm
Location: Pearland, Texas

Re: brake issues after cam install

Post by CrashTestDummy »

If I'm reading the OP's reply in post #4, it looks like he was connecting the brake vacuum hose to one of the PCV breather barbs on the valve cover. I haven't done this mod but I think the brake vacuum signal needs to be from the intake manifold. That hose on our 2012 runs to the back of the intake somewhere. Most power brake systems also have a check valve inline between the vacuum booster and connection at the engine, more often than not, it's AT the booster. If you're not getting good vacuum to the booster, I'd verify this check valve is functioning properly.
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