My vacuum is @10 in park and @9 in Drive. What are you guys running? Do you use a electric vacuum pump to generate additional vacuum for power brakes?

 

I have a Comp Cams ***** Thumpr (~300 duration and ~500 lift) and have around 13" idling in neutral.

 

which lunati cam do you have or what specs? I have 13-14" with a voodoo

 

Lunati Bracket Master II Cam
Hydraulic, fair idle. Good cam for high performance street or mild bracket racing applications, has good mid range torque and horsepower.
· Advertised Duration (Int/Exh): 290/300
· Duration @ .050 (Int/Exh): 224/234
· Gross Valve Lift (Int/Exh): .496/.520
· LSA/ICL: 112/108
· Valve Lash (Int/Exh): Hyd/Hyd
· RPM Range: 2500-5500

What is your brake booster size? Mine is 9inch.

 

That vacuum is a little low for that kind of cam in a 455. I'd expect at least 14". Sure everything is tuned right and you have enough initial advance?
10" is pretty low for power brakes.

 

Check the obvious, vacuum leaks etc. I'd guess it wasn't degreed in so I'd check the cam timing. Those cams are lazy enough, having late valve timing will make it worse.

 

hey dude i have a fairly large street cam and i use a vacuum can attached to aid in my vacuum needs. I would also say it is very easy to install 1 bracket 2 hoses etc.

 

I've used that cam at least 3 times and never had an issue with power brakes there has to be something wrong or it is mis-tuned. The vacuum that cam produces is not great but should be sufficient to work the power brakes.

 

Bumped Initial timing at 14 degrees. Car runs great. Very responsive good power. Vacuum @ 11 now. I get one good pump on the brakes and then nothing.

What size booster do you have?

 

I've used the stock and the 9" with good results. Should need roughly 12" vacuum.

I would try to get a little more initial timing in but be careful to keep your total timing in the ballpark of 30-38 max depending on your compression and the fuel you use.

For example: I have one currently setup where it has 18 initial @ idle and 36 total by 3000rpm

What distributor do you have?

 

http://www.summitracing.com/parts/su...ake/oldsmobile

The distributor’s
mechanical advance is 6° @ 900 RPM, 8° to 10° @ 1200 RPM and reaches a

maximum of 10° to 11°@ 1500 RPM The vacuum advance provides 10° of advance.

So that is 20 + initial?

 

Try checking for vac leaks like CutlassEFI suggested I use a can of wd40 and spray around to carb and intake and check those hoses. Then check the carb then the distributor if all is well you should have 12 to 14 at idle with that cam. I have 6 different Lunati cams and I never have had a problem with vacuum. Good luck.

 

True, try that first.
But this ain't really a Lunati cam. Most of these generic cams are ground by Camshaft Machine in the midwest and they sell for less than $100.00. These are done with old GM lobes and aren't anywhere near what is available today, from anybody.