i was looking at some vacuum canisters at Summit racing. do these things work very well? i am doing a engine rebuild with a larger cam and i have power brakes.

 

id go to the junkyard and find a turbo car and pull the pump and vacuum can off of it

 

Or you could just use Rhodes lifters when you install the cam.

 

ive never used the summit one, but i have the moroso vacuum pump on mine and it works great

 

I used these when I swapped cams a couple years ago (on 2+2GT's recommendation). I absolutely love them. I went with a more aggressive cam during the swap (XE268H to a Magnum 280H), but low end power actually improved. I still only pull maybe 14" of vacuum at 750rpm, but that has to be better than without them, and it goes up quickly if you up the idle to 950.

However...they're noisy, especially if you have headers. The action of the lifters collapsing allows the valves to slam into the seats, creating what sounds almost like solid lifter valve lash once the motor is warmed up. Not quite that loud (it would be less apparent with exhaust manifolds), and it goes away above 3k rpm, but it's something to keep in mind.

 

I used these when I swapped cams a couple years ago (on 2+2GT's recommendation). I absolutely love them. I went with a more aggressive cam during the swap (XE268H to a Magnum 280H), but low end power actually improved. I still only pull maybe 14" of vacuum at 750rpm, but that has to be better than without them, and it goes up quickly if you up the idle to 950.
I first used these lifters in boats, which run very differently than cars, at or near wide-open-throttle, yet you need low idle to be able to get to the dock. I was able to get Crane Fireball cams to idle at 400 rpm.

However...they're noisy, especially if you have headers. The action of the lifters collapsing allows the valves to slam into the seats, creating what sounds almost like solid lifter valve lash once the motor is warmed up. Not quite that loud (it would be less apparent with exhaust manifolds), and it goes away above 3k rpm, but it's something to keep in mind.
Since two of my cars have actual "solid" lifters, with the actual noise they make, I tend to laugh at the folks who complain the Rhodes is noisy. Especially the ones with 2 1/2" exhaust and Flowmasters. Worrying about mechanical noise from the engine was where those stupid nylon cam gears came from.

 

A vacuum canister can't increase the amount of vacuum available for the power brake booster. The only thing it does is store some vacuum which can help, but after a few stops that reserve from the canister is gone. Imagine getting into stop and go traffic and after the first couple stops you then have to use both feet to stop the car. If you have low enough vacuum that the power brakes don't operate right, the real solution is a separate vacuum pump as was suggested earlier. You can either go to a salvage yard, or they are available new and are about $200 if I remember right.

 

Well, you are assuming the engine is not running between these lights- When I approach a traffic light, I let off the gas, which pops the engine up to it's maximum vacuum, instantly regenerating vacuum available.

Or you could just build an engine that will operate the brakes properly.

 

No, I am not assuming the engine is not running. Even if the engine is running, if it is not capable of supplying enough vacuum at idle for the brakes without the canister, then the canister is only a buffer that will get you maybe an additional stop or 2 before the vacuum is too low for the booster. Yes blipping the throttle will build vacuum, but it is the bush league way to do it in my book.

You are assuming stop and go traffic is light to light, but to me stop and go is roll forward 10 feet stop, roll forward 10 feet stop, roll forward 10 feet stop........ No chance to slap the throttle plate closed unless you have a stick shift or you want to constantly shift your automatic into neutral. Also, while slapping the throttle plate closed does as you say, this is not good enough in my book as brakes are WAYYYY more important than anything else on the car. I want mine to work the way they are supposed to just by pushing the brake pedal. No tricks, no blipping the throttle, or anything like that just to keep the vacuum high enough. If it means a milder cam, or a vacuum pump, then that's the way it is.

 

Gothcha, that's not really "stop and go", that's just "stop". If your idle vacuum is inadequate, something's got to give. The Rhodes lifters will bring the vacuum up 2-4", and give you a wider power band to boot. Or you could ditch the booster and go with the MICO master cylinder, the downside is it's a single cylinder, the upside is the pedal effort is almost as low as a stock booster. Shelby used them on the GT350H so rental customers wouldn't have high pedal effort, and they avoided using a booster to do it.

I'm not a big fan of vacuum generators, always seems like just one more thing to have brake problems with. My Mustang doesn't have power boost, either. Just power.