How much vacuum should there be? - Team Camaro Tech
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post #1 of 11 (permalink) Old Jun 17th, 02, 03:47 AM Thread Starter
 
Join Date: Apr 2002
Location: Hanover Park, IL
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At idle I am measuring 11 inches of vacuum either from manifold or under butterfly vacuum port on Carter 650 cfm carb. Vacuum goes up to 18 to 19 at about 1800 to 2200 rpm. When deaccelerating it spikes up to 22 to 24 inches. 18 inches vacuum is needed to properly operate power brake booster.
I have called the engine builder and the cam company and everyone says that there should be enough vacuum or there is enough vacuum built into the cam.

Here is what I have; 406 SB (.030 over) Compression ratio is either 9.1 :1 or 10.2:1 (I'm not sure on the cc size of the head). The Extreme Energy Comp Cam is an CS XE284H-10 grind (Lobe Seperation 110 Degrees, Lift is .507 Intake/.510 exhaust, Duration 284 intake/296 exhaust. I have 1.5 roller tip rocker arms as well.

What kind of vacuum should I have and if it isn't enough based on these specs any ideas on where to look? I have already ruled out a vacuum leak to the transmission (TH400) vacuum modulator.

Thanks.

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post #2 of 11 (permalink) Old Jun 17th, 02, 04:33 AM
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Carl
 
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With that cam 11 inHg is about right.

My 406 with Comp XR282 (230/236 @0.050" hydraulic roller) makes 12"-13" at idle.

Are you having any vacuum accessory problems?

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post #3 of 11 (permalink) Old Jun 17th, 02, 05:07 AM Thread Starter
 
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CarlC. There are no vaccuum accessories. I have a 69 Camaro Z28 clone. No A/C or anything. The issue I'm having is with producing enough vacuum to work the power brakes. I want to confirm that I don't have any problems other than the way the engine configuration that is causing this. I know there are vacuum pumps of sorts but before spending the bucks I wanted to verify the vacuum readings in the forum.

Is there anything that you know that can help with increasing the vacuum that doesn't involve pumps or cannisters?
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post #4 of 11 (permalink) Old Jun 17th, 02, 05:08 AM
DjD
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I can concure with Carl on this my 280H-R10 ([email protected]") is in the 12-13 range as well. I don't know what is recomended at idle for power brakes but I don't have a brake problem. I have posted before that I was idling with my foot on the brake rolling down a hill at 3mph (looking for an address) when the pedal went hard. I shifted to neutral shot a small 1500 rev and the brakes came right back. This has never happened in traffic or crusing the hwy.

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...Dennis
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[This message has been edited by DjD (edited 06-17-2002).]
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post #5 of 11 (permalink) Old Jun 17th, 02, 05:25 AM
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you should be fine im running a 400 also .40 over 10.3 comp. with pro1 heads, with dart koolcan intake my cam is a howards max effort solid roller in the mid 6s. i only get about 8-9 inches of vacum but get along ok with a small canister for my brakes.
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post #6 of 11 (permalink) Old Jun 17th, 02, 05:35 AM Thread Starter
 
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DjD /Storman. So I can see I really don't have an issue. Great! Storman you say you are using a cannister is that for your power brakes? Since at above idle, vacuum is plentiful. How long will the cannister store enough vacuum? Did you turn up your idle slightly to help that along when in stop and go traffic? Or does that cannister really work that well? Sorry to seem like such a skeptic. I bought this car a few months back and have had my share of surpises!
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post #7 of 11 (permalink) Old Jun 18th, 02, 05:14 PM
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i used the small crane canister and it supplies just enough for around town (bigger would be better here) but a quick throttle raise always fills it. with this cam i cant really idle below 950 so any more is out of the question. you should be fine an by the way do you have the correct line on your booster an valve (check valve) at the booster an is the booster an valve operating properly
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post #8 of 11 (permalink) Old Jun 19th, 02, 03:34 AM Thread Starter
 
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I'm running a 3/8" i.d. line from the intake manifold to the booster. The check valve works fine. The power booster was questionable at first but I had "ripped" the rod out in my attempt to shorten the rod to get brake pedal 4 1/2 inches above floor. That's what started this whole investigation. I'm going to have the power booster rebuilt and replace the MC. The MC is leaking from around piston seal. Everything that was supposedly replaced has turned out to be junk. Oh well, that goes with the territory.
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post #9 of 11 (permalink) Old Jun 19th, 02, 05:42 AM
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Mark
 
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John Z recently told me his stock DZ 302 pulls about 9" at idle and we have stock power brakes if that helps at all.
www.brakeboosters.com rebuilt and replated my booster, MC cover and big nut valve bracket for me for a package deal price. Very nice work. I had my original M/C brass sleeved for about $75 from Apple Hydraulics and installed a rebuild kit and all was good as new for me. All restored to show quality.

-Mark.
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post #10 of 11 (permalink) Old Jun 19th, 02, 06:42 AM
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Comp cams now offers this info on their website. FYI

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post #11 of 11 (permalink) Old Jun 19th, 02, 08:46 AM Thread Starter
 
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I had spoke with Steve Gregori last night and had gone over some options for my Power booster. He'll be getting my business. I checked out that Comp Cams website like you suggested and there it is in black and white for vaccum readings. Thanks for that info. I'm going to go onto the next item on my car that needs attention. Thanks everyone.
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