Vacuum - it really sucks!!!

Docmacs'77 · 08-21-05, 06:17 AM

Actually, I don't think it's suckin' hard enough! Here's the deal. I finished my 383 stroker and dropped it in. In addition to fixing/replacing several things, I also replaced all four calipers and bled the lines but the brake light is still on. Whereas, before exchanging engines, when I hit the brakes I'd feel the pedal go solid at about an inch in. Now, the pedal goes down about 3/4 of the way before it's solid. I ran a vacuum check today (at the front port of my Holley 4160) and it was pulling 15 inches. I've read somewhere that it should be about 20 to 22 inches for the power brake booster and the headlights to function properly. But obviously, if you've got a performance cam, you're going to lose some vacuum. I've got a fairly lopey cam, but nothing majorly radical (480 lift/232 at .050) IF this is the reason, i.e. not enough vacuum, can you suggest a good vacuum pump I should get? Or any other ideas/suggestions?
Thanks, Marc.

gmjunkie · 08-21-05, 07:41 AM

I don't think you'v got all the air out of Brake Syst. These can Be a Bastxxx sometimes!!

junk!!

gedmeyer · 08-21-05, 09:31 AM

I agree. It's a real pain to bleed the brake lines. The brake light indicates that there is an imbalance in line pressures between the front and rear brake systems. I'm running a 383 with a 470 lift cam and have plenty of vacuum to work my brakes.

If you search the forums, you'll find a ton of posts concerning what bleeding technique/procedure works for different people.

-Tim

AKRAY4PLAY · 08-21-05, 04:27 PM

as said, your brakes need more bleeding. i have 9 inches of vac at idle with motor and the brakes and lights work, not great but they work. also check that your check valve on the vac booster is working and not leaking. 15 inches of vac is more than enough to operate the lights and brakes.

Docmacs'77 · 08-21-05, 05:12 PM

Air still in the lines..............I bet your right. I'll re-bleed. BTW, AKRAY4PLAY, could you give me a hint on where the check valve is and the best way to check it? (Had my Haynes laying around in the garage awhile back, but it just disappeared! Go figure, like there's very few C3's running around here, so why would somebody want to steal a corvette manual? I'm pretty sure somebody picked it up - there were several guys over when a buddy of mine and I were working on the car. Guess it's time to buy another one.) Marc.

AKRAY4PLAY · 08-21-05, 05:26 PM

Marc,
the check valve is the little plastic thing that your hose hooks to on the vacuum booster. you can pull it out and do the mouth test to see if it works right. if not, they are about two bucks at NAPA or anyother parts place. my rubber grommet was dry rotted and playing havic with tuning. hate those intermittent vac leaks.

Docmacs'77 · 08-21-05, 06:05 PM

Quote:

Originally Posted by AKRAY4PLAY

Marc,
the check valve is the little plastic thing that your hose hooks to on the vacuum booster. you can pull it out and do the mouth test to see if it works right. if not, they are about two bucks at NAPA or anyother parts place. my rubber grommet was dry rotted and playing havic with tuning. hate those intermittent vac leaks.

Thanks for the quick response AKRAY4PLAY. I'll check it out. Seeing as how the brakes are such a pain to bleed completely (I really hope I bled them completely the first time) I think I'd much rather have it be the check valve. Thanks again, Marc.

AKRAY4PLAY · 08-21-05, 09:14 PM

Marc,
not trying to bum you out, but it took me three bleedings to get mine working good. i bleed mine in the suggested order, LR - RR - LF - RF. start with the inside bleeder first, then do the outside for each wheel. i found having a helping foot to pump the system with pressure before bleeding. stay with it, she'll tune with time. Brian.

gmjunkie · 08-22-05, 06:20 AM

Jack Butt of Car as far as you can and set on stand's! Get the incredable Hulk, or Equv. to Pump the brake agress and Stand on Brake pedel!! Start Rt rear inside,then Rt R outside. Then L rear inside,then Lt R outside!! Then Rt front and Lt front !! This may take 2 or 3 or more times!! Brake Pumper must be agressive !!

If you can't find a Hulk or Equv. ( JonM ) with Nude Photos Pamala Anderson pasted to inside of windshield will work!!

junk!!