I saw this in a post about someone having low vacuum for his brakes.

What does this do ? Does it really help ?

thanks !

Tom

Tom,
Can you search and find the original post you are refering to?

Joe

It's about half way down this page at check valve (http://www.chevelles.com/forum/ultimatebb.php?ubb=get_topic;f=7;t=005843)
Originally posted by bulb122:I wouldn't worry about it one bit, use the power booster. If you have 12" of idle vacuum I think your power discs will work just fine, you won't need a vacuum pump. I have 6" idle vacuum and my 72 power discs work just fine. The only thing i did was add a vacuum check valve from an 80 Z28, but I really didn't notice a huge difference adding that. I vote fo putting on the parts you have, and have a good time! The guy doesn't say why he put it in but itsounded like it might help a low vacuum problem.

Tom

I got the check valve at O'Reilly in the HELP! section for a couple of bucks. It works. When I kill the engine with my foot on the brake I can hear the brakes slowly release as the vacuum bleeds off. Without my foot on the brake, I can hear the vacuum bleeding off slowly.

The check valve/grommet kit for an '80 Camaro w/350 engine is $10.79 (list) at O'Reilly. It's listed on their website as AC Delco Part #179-1265.

Hi Chad !

Was the leak from the vacuum check valve and grommet or from the seal behind the master cylinder ?

The bleed down comes from the grommet, not the booster.

I hope I'm not leading anybody astray by mentioning that my brakes work fine with so low of vacuum..... Just to double check, I measured the vacuum at idle again, and it's 6.5-7". From what I've read, i thought I should be having trouble with my power brakes. I have a 1968 master cyl and booster (i think meant for 4 piston calipers). I used 72 front single piston discs, and in the rear I have a 69 olds type "o" rear axle with it's drum brakes. I used an adjustable prop valve in the rear line, and that's about it. Maybe it's the combination that works ok with low vacuum?

Anyway, I didn't have any trouble without the check valve. But reading that people had trouble with their brakes made me wonder if mine were intended to work better than they were. I had a check valve from my parted out beater camaro, so I decided to put it on the chevelle and see what happened. I have a four speed with low 4.66 gears. at any rpm above 2000 while decelerating in gear the vacuum is really high, like 25. So when i put in the check valve, I didn't really notice any difference. I left it in there though. I think maybe if I pushed in the clutch and let it idle down while I was decelerating at low vacuum, maybe it would react different. I don't really know..... smile.gif

I think the check valve would be a cheap score at the boneyard......

chris