Brake booster vacuum

[aheathdc]

I installed a Right Stuff power brake booster, previously had manual brakes. It works better after driving for a bit but still doesn't stop like it should. I'm pulling vacuum off the manifold in front of the MC2150 carb, vac is 15 inches. Right Stuff says it should be 16-18 inches. Is the difference enough to impede brake performance? My AMC 304 was rebuilt about 1000 mi. ago. What is good vacuum reading for that engine? Thanks

 

[Torxhead]

I would suggest finding another location and check the vacuum from there. That is a pretty weak reading from a fresh engine. Check your ignition timing also.

 

[aheathdc]

I will check the timing to see whether that changes the vacuum. I drive my jeep at sea level and about 7k feet here in AZ so I do have to change it depending on altitude. Thanks

 

[Lumpy Grits]

15hg is low for PHX. What altitude do you live at?
My stock AMC 258 i6 / 4.2l pulls 18-19hg @ 2700' ASL.
You may have to add a vacuum storage can.
Anything under 16Hg and the system will suffer.
LG

 

[aheathdc]

I'm at about 1000 feet. I know I retarded the timing when I was on the beach in Mexico with it this spring, started pinging and getting hot. Moved the distrib. about 2 degrees and it ran like a champ, may have not advanced it back since then. Thanks

 

[Torxhead]

You can set your ignition timing with a vacuum gauge. Adjust the timing to the highest vacuum reading then back off one degree, lock it there. This method is posted on the net. That vacuum canister does sound like a good idea as the later CJs did have them.

 

[aheathdc]

I know mine came with a charcoal emissions canister but nothing to do with vacuum. I will look into the vacuum canister. Thanks

 

[Lumpy Grits]

Get a timing light and set it 'rite'.
Check the idle air/fuel mix adjustment.
You may well have a vacuum leak.
You'll want to do this before your next SMOG test.
LG

 

[Torxhead]

I know mine came with a charcoal emissions canister but nothing to do with vacuum. I will look into the vacuum canister. Thanks

In the later CJs it was called a vacuum reservoir with check valve. It looked like a small can.