Vacuum Brake Users

Steve Wood · 09-21-2005, 11:02 AM

There was a question/answer in the tech section of the November issue of Car Craft regarding vacuum brakes. I thought the comments regarding the master cylinder, boosters, and vacuum levels were interesting altho I am a bit confused on some of the vacuum levels versus booster size...either I am reading challenged, or there may be a typo...

Anyway, I scanned the article:

http://www.vortexbuicks-etc.com/vacuum_brakes.htm

EricStage1 · 09-21-2005, 11:51 AM

Must've been a mistake. Where it says "between 9 and 20 in-hg" they must've meant "between 15 and 20 in-hg" to use a 9 inch diaphragm. I guess?

Eric

TurboBuickSix · 09-21-2005, 01:10 PM

It says GM boosters need 15 in hg of vacuum (in drive)to operate properly.Anyone have that much vacuum on their motor in drive at hot idle? I know with my 204/214 that I do not.11 in at best,hell we have a single plane intake,no wonder vac brakes won't hold boost sometimes.I did not like the feel of vac brakes on one of my cars I converted and the PM admittedly makes me nervous.Will our stock PS pump be sufficient to run a hydroboost setup like a hot air uses?

Steve Wood · 09-21-2005, 01:23 PM

Eric, that was my interpretation based upon the logical progression of the diameters.

Dave, I had about 10-11 with a 221 deg cam which used up the vacuum quickly if I got off and on the brakes repeatedly.

With my 210 roller, I have 12 in drive with the ac on, and the vacuum brakes work well.

My other cars have 15 in drive with stock cams.

In general, I think their comments are pretty close.

I noted their comments on the electric vacuum pump with interest...perhaps it does not provide enuf vacuum volume quickly enuf to maintain the brakes?

Red Regal T · 09-23-2005, 07:25 PM

For vacuum brake use with bigger cams, electric vacuum pumps would probably take care of low vacuum numbers.

instro84 · 09-23-2005, 08:09 PM

Dave i hae a hot air car converted to LC2 and kept my hydroboost with the stock ps pump and it works fine.

09-21-2005, 11:02 AM	#1 (permalink)
Steve Wood Scam Detector Enabled Join Date: Sep 2000 Location: East of Eden, Texas Posts: 41,369	Vacuum Brake Users There was a question/answer in the tech section of the November issue of Car Craft regarding vacuum brakes. I thought the comments regarding the master cylinder, boosters, and vacuum levels were interesting altho I am a bit confused on some of the vacuum levels versus booster size...either I am reading challenged, or there may be a typo... Anyway, I scanned the article: http://www.vortexbuicks-etc.com/vacuum_brakes.htm __________________ ------------------ A proud member of Stonewallers Against Bogus Technology Fix reason firmly in her seat, and call to her tribunal every fact, every opinion. Question with boldness even the existence of a God; because, if there be one, he must more approve of the homage of reason, than that of blindfolded fear. Thomas Jefferson . www.vortexbuicks-etc.com

09-21-2005, 01:10 PM	#3 (permalink)
TurboBuickSix Not a Selfproclaimed guru Join Date: May 2001 Location: Buffalo,NY Posts: 418	It says GM boosters need 15 in hg of vacuum (in drive)to operate properly.Anyone have that much vacuum on their motor in drive at hot idle? I know with my 204/214 that I do not.11 in at best,hell we have a single plane intake,no wonder vac brakes won't hold boost sometimes.I did not like the feel of vac brakes on one of my cars I converted and the PM admittedly makes me nervous.Will our stock PS pump be sufficient to run a hydroboost setup like a hot air uses? __________________ Dave Schreiber,86 GN. 12.00@114 1980 Berlinetta Camaro 40k miles

09-21-2005, 01:23 PM	#4 (permalink)
Steve Wood Scam Detector Enabled Join Date: Sep 2000 Location: East of Eden, Texas Posts: 41,369	Eric, that was my interpretation based upon the logical progression of the diameters. Dave, I had about 10-11 with a 221 deg cam which used up the vacuum quickly if I got off and on the brakes repeatedly. With my 210 roller, I have 12 in drive with the ac on, and the vacuum brakes work well. My other cars have 15 in drive with stock cams. In general, I think their comments are pretty close. I noted their comments on the electric vacuum pump with interest...perhaps it does not provide enuf vacuum volume quickly enuf to maintain the brakes? __________________ ------------------ A proud member of Stonewallers Against Bogus Technology Fix reason firmly in her seat, and call to her tribunal every fact, every opinion. Question with boldness even the existence of a God; because, if there be one, he must more approve of the homage of reason, than that of blindfolded fear. Thomas Jefferson . www.vortexbuicks-etc.com

09-23-2005, 07:25 PM	#5 (permalink)
Red Regal T BUICK LOVER Join Date: Sep 2000 Location: Zephyrhills, Fl USA Posts: 1,260	For vacuum brake use with bigger cams, electric vacuum pumps would probably take care of low vacuum numbers. __________________ John DiCarlo GSCA #52 87 RED REGAL T 87 DARK RED T 87 GRAND NATIONAL MANY PHOTOS HERE

09-23-2005, 08:09 PM	#6 (permalink)
instro84 USAF retired Join Date: Jan 2004 Location: edwards afb Posts: 358	Dave i hae a hot air car converted to LC2 and kept my hydroboost with the stock ps pump and it works fine. __________________ 87 T undergoing major reconstructive surgery

09-21-2005, 11:51 AM	#2 (permalink)
EricStage1 Registered User Join Date: Jan 2001 Location: Salem, Illinois Posts: 328	Must've been a mistake. Where it says "between 9 and 20 in-hg" they must've meant "between 15 and 20 in-hg" to use a 9 inch diaphragm. I guess? Eric

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