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Effective power brakes with big cam #1385794 02/11/13 07:42 PM 02/11/13 07:42 PM
Joined: Jan 2003 Posts: 738 Oh Canada E EV2CUDA OP super stock
EV2CUDA OP super stock E Joined: Jan 2003 Posts: 738 Oh Canada	What is a good solution to retaining power brakes when running a big cam or supercharger? I want to retain the booster on my ebody. Electric vac pump? Where to place it? 71 Barracuda 383 4spd (500ci) 69 camaro 598, NOS 69 barracuda bbc procharger 77 t/a 6.0 turbo project 78 t/a 400 77 corvette 1983 hurst/olds 03 Viper 79 360 macho 71 demon 360 78 Warlock 5.7 hemi project

Re: Effective power brakes with big cam [Re: EV2CUDA] #1385795 02/11/13 08:49 PM 02/11/13 08:49 PM
Joined: Feb 2010 Posts: 18,493 Granite Bay CA Kern Dog Striving for excellence
Kern Dog Striving for excellence Joined: Feb 2010 Posts: 18,493 Granite Bay CA	I put a vacuum tank in the Charger, behind the headlights but in front of the left front tire. There is plenty of dead space there in an E body as well. I have a MP '509 cam in a 493/440. Its a bit choppy and the power boosted brakes needed the crutch. Mine works fine.

Re: Effective power brakes with big cam [Re: EV2CUDA] #1385796 02/12/13 12:03 AM 02/12/13 12:03 AM
Joined: Mar 2008 Posts: 5,746 Ontario, Canada Dodgem master
Dodgem master Joined: Mar 2008 Posts: 5,746 Ontario, Canada	I just kept full mechanical advance by 1200 and kept idle 1100 to 1200 in gear! was fine up to a big roller 272/282 @ .050 only took booster off last summer cause after 44 years it was kaput! Last edited by Dodgem; 02/12/13 12:03 AM.

Re: Effective power brakes with big cam [Re: Dodgem] #1385797 02/12/13 12:45 AM 02/12/13 12:45 AM
Joined: Jan 2007 Posts: 7,664 IN A ahy master
ahy master A Joined: Jan 2007 Posts: 7,664 IN	"By the book" the vacuum assist needs around 18" idle vacuum. Mine and others seems to work OK in the real world with 12-13". Below that expect issues at least sometimes. A vacuum pump or hydro boost is the best solution. A can may help but may still let you down when you need it.

Re: Effective power brakes with big cam [Re: EV2CUDA] #1385798 02/12/13 08:26 AM 02/12/13 08:26 AM
Joined: Mar 2007 Posts: 3,285 West Coast, USA jbc426 master
jbc426 master Joined: Mar 2007 Posts: 3,285 West Coast, USA	The power booster on my '70 works normally with a moderately large cam and only 5 to 6 hg at idle. 1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's 1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)

Re: Effective power brakes with big cam [Re: jbc426] #1385799 02/12/13 10:03 AM 02/12/13 10:03 AM
Joined: Sep 2009 Posts: 70 New Jersey Randy514 member
Randy514 member Joined: Sep 2009 Posts: 70 New Jersey	We installed an electric vacuum pump on our race car (73 Cuda)3-4 years ago when we installed a solid cam. It now has a 730 solid roller in it and the vacuum pump works great (almost better then when it ran off of engine vacuum) Mounted it on the frame rail below where the battery tray is. Got it in kit form from Napa I think. It cycles and only runs when the demand warrants it.

Re: Effective power brakes with big cam [Re: Randy514] #1385800 02/12/13 10:12 AM 02/12/13 10:12 AM
Joined: Oct 2003 Posts: 21,345 Marysville, O-H-I-O 70Cuda383 Too Many Posts
70Cuda383 Too Many Posts Joined: Oct 2003 Posts: 21,345 Marysville, O-H-I-O	my Dakota has a cam that idles at 8.5" during hot idle. it's still enough vacuum to keep my brakes happy. I can feel the pedal is a bit stiffer when I first start up and I'm maneuvering around in the driveway, pulling out of the garage, etc. but not so much that I feel like I can't stop the truck. once I'm driving and vacuum builds up, the booster keeps enough vacuum that I can get 3 or 4 full strokes of the pedal before it starts getting firm again. (which never happens unless I'm playing with the pedal) even in stop and go traffic, I have plenty of brake pressure to never feel like I can't stop. the booster SHOULD have a check valve in it that holds vacuum, and prevents positive pressure from the manifold from a turbo/supercharger at WOT. When you're cruising around at part throttle, the manifold is in vacuum and will put a charge into the brake booster. if you find that you are having problems with the brakes, you can add a tank for more vacuum in reserve, or you can buy a vacuum pump to keep the brakes happy. or go with hydro boost. or a manual brake master cylinder, or.... Photobucket sucks

Re: Effective power brakes with big cam [Re: ahy] #1385801 02/12/13 03:26 PM 02/12/13 03:26 PM
Joined: Jan 2003 Posts: 3,719 Space Station #5 471Magnum master
471Magnum master Joined: Jan 2003 Posts: 3,719 Space Station #5	Quote: "By the book" the vacuum assist needs around 18" idle vacuum. Mine and others seems to work OK in the real world with 12-13". Below that expect issues at least sometimes. A vacuum pump or hydro boost is the best solution. A can may help but may still let you down when you need it. I think this is a pretty good rule of thumb, but note that a good ignition curve with 18-20 degrees of initial advance does wonders to get the vacuum up at idle, even with hairy cams. -Jim I can fix it... my old man is a television repairman. He's got the ultimate set of tools... I can fix it. Currently Mopar-less

Re: Effective power brakes with big cam [Re: 471Magnum] #1385802 02/13/13 12:23 AM 02/13/13 12:23 AM
Joined: Jan 2003 Posts: 738 Oh Canada E EV2CUDA OP super stock
EV2CUDA OP super stock E Joined: Jan 2003 Posts: 738 Oh Canada	I ordered a vac pump from jegs as they are on sale. What is the proper procedure for testing the booster for holding vacuum? I dont have an engine in the car right now. BTW the cam I have is a 262@50 solid roller in a 499. 71 Barracuda 383 4spd (500ci) 69 camaro 598, NOS 69 barracuda bbc procharger 77 t/a 6.0 turbo project 78 t/a 400 77 corvette 1983 hurst/olds 03 Viper 79 360 macho 71 demon 360 78 Warlock 5.7 hemi project

Re: Effective power brakes with big cam [Re: 471Magnum] #1385803 02/13/13 12:43 AM 02/13/13 12:43 AM
Joined: Jan 2007 Posts: 7,664 IN A ahy master
ahy master A Joined: Jan 2007 Posts: 7,664 IN	Quote: Quote: "By the book" the vacuum assist needs around 18" idle vacuum. Mine and others seems to work OK in the real world with 12-13". Below that expect issues at least sometimes. A vacuum pump or hydro boost is the best solution. A can may help but may still let you down when you need it. I think this is a pretty good rule of thumb, but note that a good ignition curve with 18-20 degrees of initial advance does wonders to get the vacuum up at idle, even with hairy cams. Agree... mine needed the good ignition curve (20 deg advance) and fine tuning of idle AF to get to the 13" range. "Before" it was in the single digits. PS: My cam is 243@.050, 108 CL. With 262@.050 I think the pump is a good choice. Last edited by ahy; 02/13/13 12:50 AM.

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