Vacuum Can or Pump?
 

I was curious to those who have a larger cam with power assisted brakes what you use for Vacuum assistance. Is there a cam profile lift, durations? that determines when to move from a Vacuum can to a pump assisted vacuum? I have the Competition Cam 308R Solid Roller with 575 lift 262 duration and have already installed a Vacuum cansiter, but was a little worried to the affects of stop light to stop light braking etc.

Remember, that the vacuum canister will hold vacuum based on your maximum achieved vacuum before being depleted. While the engine may only make 8-10" at idle, if it makes 16 at cruise, the vacuum can is holding 16" until it's depleted and refilled.

For the street, if you're playing light to light that can be detrimental because if you're hard on the throttle and need to get on the breaks, your vacuum can may have only seen a couple inches of vacuum at best. Can really put you in a sticky place. As a result if you are unwilling to go to manual or hydroboost brakes, on the street I would favor a vacuum pump.

Ultimately a well setup manual break system or a hydroboosted brake system for street use with a radical engine is going to be your best bet IMHO.

Hmmm, I actually threw away some manual brakes I had for the car back in the past. I will have to look into this some more. In the past, I had a fresh build on my 400 with a mutha thumpr cam and it also had a vaccum leak that caused very low vacuum at idle and I had a vacuum can and there was no issues, however the cam profile is different. I may call Comp Cams and see what they recommend aswell for this application.

How many CID are we talking about here, because assuming the same Size combustion chamber a 455 will make 13% more vacuum then a 400 with the same cam.

Just called comp cams, and they recommend a pump as well. Thanks for the advice. I will probably keep the canister and install an electric pump.

I went hydroboost and its awesome

This is a 455 stroked to a 495.

How much vacuum do you have now???

With an engine that big, the FIRST thing I'd do is look at the fuel curve, and ignition advance. I bet that engine can be tuned so it makes better vacuum. It'd be more fun to drive, too.

The enginehas only been on the Dyno so I dont know?

Try it and see how it works, before you buy more equipment to stuff under the hood.

MAYBE it's going to be OK without the vacuum pump. Might depend on the size/configuration of your booster.

hydroboost for the WIN!

Manual Brskes here. Simple, fewer problems, less costs.

Sounds like a good plan. I will do that. It appears a good vacuum pump can be $400 shipped. I can be patient :)

I have actual experience with ONE vehicle that has hydroboost. A sample size of ONE is not much of an indicator...

...but the pedal "feel" with Hydroboost on my '97 K2500 is goofy. Brakes are bled, including using a scan tool to chatter the ABS solenoid valves. Friction material and iron in good condition. Brake hoses OK. Stops fine, but takes some getting used to compared to vacuum boosters.

If you don't mind, what does a 'goofy' pedal feel mean to you?

I'm having to try a hydroboost system from Right Stuff to replace their standard 4 disc conversion that would not adequately stop/lock up the brakes. Curious what to expect and this is the first negative feedback I've heard about hydroboost.

Dead. No feedback. Over-boosted. Are all Hydroboost systems like this? I don't know. Like I said--sample size of one.

Similar in concept to middle-'60s Chrysler power steering--no "feel", spin the wheel with the tip of one finger. Completely, totally numb. Heaps and piles of assist, entirely lacking in "road feel".

i run a v.pump from CVR
it's two wires, adjustable for altitude and has been working for 12+ years
i also have a 1" bore master, that had made a difference too
manual brakes certainly cleans it all up nicely
i can only imagine the pressure hyrdoboost would make,,, my only experience with them has beein in trucks, and if it works for them, can only imagine how it would do on a car

I always used manual brakes on my street/strip cars. It's cheap and uncomplicated and it leaves lots more room.

X2 on try it 1st! . Mine actually has too much assist butt has a dual diaphram booster from a 79 to clear the tall valve covrrs

Having quite a number of mustangs in the past, they all had hydroboost on them. Compared to a vacuum booster they can feel mushy with several notches in the pedal throw as the hydraulic pressure is purged etc.

They don't tend to ramp as pressure as added, so they kind of feel the "same" regardless of the amount of pressure you are exerting. The hydraulic pressure dampens feedback through the pedal so it's hard to tell when the tires are on the limit.

Hydroboost is great for cruisers and hot street cars that want power breaks but don't need them for any type of real racing activity. You almost never see hydroboost on any serious auto-x or open road race vehicle specifically because there's almost no feedback for the driver.

If that's not a concern for the OP, I'd go hydroboost over messing with vacuum cans or pumps.

Hydroboost? I wouldnt recommend it. Not only is the pedal feel really bad, your "assist" can be affected by something as dumb as the PS belt tension. I've also panic stopped a hydroboosted GMC crew cab that was pulling an open trailer with a car on it. I dont ever want to be in that situation again. EVER. An evasive maneuver combining heavy steering effort and heavy braking effort is a bad deal.

Not a fan of vacuum cans, for the same reasons as already mentioned.

I have more than one car with manual brakes, and one of them is a disc/drum street car. With the right combination of parts, the pedal feel and feedback is hard to beat in my opinion.

2 cars and 2 trucks here with hydroboost and never an issue. Love the pedal assist. Works as intended, rock solid pedal feel on all of them.

Used to run vacuum cannisters with "OK" results but still only good for about 2 stops when idling around a parking lot. Then tried electric vacuum pumps, got really tired of the noise they created.. Went through all that for years before throwing in the towel for hydroboost and now won't ever look back.

On a hot street car it's either going to be power brakes with hydroboost or a manual brake system. That's it.

To play devil's advocate here, the brake sizing on those mid 90's chevy light and medium duty trucks/suv's was piss poor. Hyrdoboost isn't necessarily the issue as much as the fact that GM put brake rotors and calipers on those vehicles that were originally on late 60's to early 70's cars that weighed 1500-2000 lbs less and weren't towing trailers.

Hydroboost is one part of the brake system, it can't make up for extremely undersized brakes with sheer line pressure.

When it comes to trucks, I've only had hydroboost on the 3/4 ton and 1 ton trucks we had. All of which have massive brakes on them.

My 79 1 ton had it, and up until the day I sold it a few years ago, the factory system was still working flawless. I owned that truck 25 years and never had a single issue with it.

Had hydroboost, but as mentioned a properly set up manual brake system is the way to go here. Cleaner, simpler, less to go wrong and not expensive.

No argument from me.

The "big problems" with the GMT400 trucks were especially pronounced on the 1500 series; but those were by far the most-produced. There were enormously fewer 2500 and 3500 series trucks made compared to the 1500, and the heavier-series trucks also had much better brakes.

The 1500s had a crappy rear axle originally designed for compact and intermediate-sized cars. GM had no business putting it under a full-size pickup. That axle was almost universally equipped with 254mm (10") leading-trailing shoe drum brakes that require the park brake to be used in order to maintain shoe adjustment. Since nobody uses the park brake, the shoes are perpetually far from proper adjustment. Making things even worse, the front shoe on each side does all the forward braking. Which is why the front shoe will be worn-out long before the rear shoe--which does the majority of braking in reverse.

The first few years of that truck series, the regular-cab 1500s got a miniscule power booster, thin rotors, small-bore master cylinder, and tiny caliper pistons. Even GM acknowledged that the JN3 brakes were under-powered, in the early '90s they increased the braking power to JN/JB5 series brakes--what had come on the extended cab 1500s all along. But they still had the horse-crap leading/trailing shoe rears.

A rear-axle swap that replaces the junk 8.5" ring gear, 10-bolt axle with the 9.5" semi-floating 14-bolt cover axle also upgrades the rear brakes to proper 11.x Duo-Servo drum brakes where both shoes stop the vehicle.

Don't get me started on folks who think they can bleed ABS brakes on the post-1990 GMT400 trucks without using a scan tool to chatter the solenoids.

I had a 3/4 ton truck engine die going down the freeway with the hydroboost system with me driving and doubt the wife could have got the truck stopped quickly and safely. It was a handful.

We've had three club members recently that followed the yellow brick road to more radical cams and all three are very happy swapping to manual brakes. Always the same pedal effort on each stop regardless of what the engine is doing. The drag car with manual brakes and the 4-wheel disks can be locked up pretty easy and that's a small disc system.

Power steering is the same way. If the car dies, it's extremely difficult to even steer the car, much more so than a manual steer car. Not many people can deal with that either. I know my wife couldn't, but the cars she drives has to have power steering. That's just the chances we have to deal with on most any car. Been that way forever.

I do like manual brakes, and one car in the stable still has them. While it could use an upgrade (4 wheel drum) to some disc up front, that car will stay manual brakes and manual steering. I do like the simplicity of one fan belt and not much else under the hood.

If your hydroboost dies when the engine stalls, you need a new accumulator. There should be enough stored pressure in the accumulator for a couple of additional stops. The analogy is to a vacuum booster that stores enough vacuum for a couple of extra stops if the engine stalls.

Similarly, if you have heavy demand for both the hydroboost and power steering, the hydroboost should be unaffected because the accumulator has stored energy.

Yes and as an example of that, I've pushed the car outside on occasion, on a downward slope, and it still has power assisted brakes without the engine running.

I have that same cam in a build I just did for my 57-Wagon project
I'll let you know when it comes together, Probily be to late though

GT