I am needing some suggestions on sorting out my power brakes! Most of the stuff is from Speedway, 4 wheel GM Metric disc brakes, rears have mechanical parking brake. Single diaphram booster with Corvette style master cylinder, 1 1/8 bore The engine is a small block Chevy 383 stroker with a vintage Babe Erson cam that I have some info on. The duration, 218 degrees @ .050, 104 degree lobe separation, lift .456 Int, .449 Exh. Pretty lumpy @ Idle. Intake manifold is Edelbrock Performer EPS with Edelbrock 650 cfm #1406. I wonder about where to pull the vacuum for the brake booster? Right now the vacuum is coming from the top right side of the intake manifold. I know that the carb has a large vacuum port in the back-middle above the base which is now plugged. What about vacuum pumps or canisters? The brakes willl stop the truck but just not good enough to lock them up or stop fast! Help me out! Thanks! Joe
Same problem here too. To big a cam, minimum vacuum and brakes don't lock up. Disc / Drum set up. We both could use some tips I hate those noisy after market vacuum pumps. Last one I had sounded like a machine gun. Anyone want to guide us.
You have 2 ways to go here, Variable Duration lifters such as the one from Rhoads like the V-Max, or you can just get a Vacuum reserve canister sold by most places like Jeggs or Summitt Racing.
I have a 559 lift in a 351 cleavland and pull about 9 inches and still have power brakes from the manifold. It could be better thou. Iwas thinking about adding a canister
Manual brakes - no booster needed, brakes work well with the engine off, run radical cams - No problems Just get your pedal ratio, MC piston size and volume right and you're good to go. I like 7/8" MC piston size for manual brakes. I use Wilwood MC, don't know about Dinosaur MC's
How well do vacuum reserve tanks work? My engine makes about 10 in. of vacuum, I've been told I need 18-20 in. for the booster.
Don't see what a vacuum cannister would do. If the vac from the engine is low, the cannister would give a resevoir but would not give any more vacuum than the engine supplies. Your'e looking for X inches of vacuum, not volumn. I doubt he's running out of vac, just has low vac.
If you install a vacuum gauge in your ride, take it for a drive and learn how principles of engine vacuum work, you will understand. It's quite simple actually and the canisters work. Will you have full vacuum stored as soon as you start your rig and back out of the driveway- no. If you can't stop in this scenario, you have a poorly or not at all engineered and designed braking system and much more severe problems than a low vacuum signal.
Some of the diesel trucks run a small electric vacuum pump and a canister, it is originally intended for operating the ac system but might work well as a booster assist. I would install the canister between the flow valve and the booster so it just draws the the booster down to a lower vacuum. DORMAN Part # 904214, just over $50 from rockauto
It shouldn't be a vacuum problem. That cam in an engine like that should develope at least 14-15 inches of vacuum at idle an 18-20 when you let off the throttle. Thaere should be a check valve at the booster that doesn't allow loss of low pressure. Could be too hard pads, linkage ratio problem or a hundred other things. Did you do any consulation with someone that knows WHAT THE HELL they're doing before you started mixing parts in the most important system on a vehicle?
One thing I'm trying to point out is that the booster IS A RESERVOIR and if the check valve is working it will maintain the inches that are developed on deceleration at least for one stop. Try it on a real car that has an engineered system. Run up to 60, turn off the engine and it will still stop if you don't pump the brakes.
a cheap canister from summit or jegs is the way to go. added one to my old mustang with a VERY radical cam and the brakes worked like new. i think i paid less then $30
Another thing I forgot- If you have the same brakes frt and rear, you will need tio have some way of balancing the force. If you ever get them to work, the rear will lockup before the frt causing you to spin out. The easiest way ( have done it on our circle burner) is to decrease the surface area of the rear pads by grinding off lining on ends until the frt lock up just before the rear.
To the O/P, most brake engineers will tell you for 4 wheel disc brakes you should be running a dual diaphram booster. DISCLOSER: Vacuum Reserve Canisters, Variable Duration lifters, Vacuum assist pumps etc., will not make up for and correct a poorly engineered braking system. They will not correct inadequate pedal ratio or a mismatched M/C, as well as any other issues of a poorly designed system. I also agree that is not much of a cam you are running, the 104 L/S is greatly contributing to the radical idle, not so much the enourmous amount of perceived duration and cam timing. I would really go over my braking system with a fine tooth comb.
If I understand correctly you have brakes but the pedal is hard and it don't slow down any better with both feet on the pedal? You need more booster, minimum 7" dual diaphram, 8" dual would be a bunch better.
Go with a canister and you shoud be fine. you need a minimum of 15 inches of vacuum for your booster to operate properly.
my point is if his engine is pulling only 10-12 inches of vac, no cannister will see any more than 10 inches of vac. It can't because that's all the engine can pull.
I would expecft that engine to make enough vacuum, but....... There needs to be a check valve in the vacuum supply to the booster. In some cases it's part of the booster, in other cases it's separate. The brake booster itself is a vacuum reservoir. If you don't have enough vacuum to start with, and axillary reservoir isn't going to fix that. There are a variety of belt driven and electrically powered vacuum pumps. If your engine doesn't produce enough vacuum the fix is either a pump or manual brakes.
Vacuum pump I have supplys 18" vac when running. It is noisy even with rubber isolators and needs to be mounted near the booster for best results. A reservoir can be used and when you decel you will get a high vac signal then when your at idle so that helps. Drive with a vac gauge and see what you vac signal is at idle and decel. Also check that your booster is working by putting your foot on the brake with car off then start it you should feel the pedal drop which means booster is functioning.
I think what Traditions is trying to say is that when you decelerate down a hill for instance, the vacuum from your engine will be much higher, so the canister stores that via it's valving so you have it available later for the brakes. So this should work, unless your engine never ever pulls more than 10-12inches even on deceleration?
Elec vacuum pumps are a lot quieter these days...Our delivery fleet had 20 all electric vehicles, and I never did hear any of the pumps (vacuum, power steering, coolant) make the slightest sound. I'd give those a second thought. 4TTRUK
I thank all of you for your ideas! The truck is presently at a friend's house having an oak roof structure built for it. As soon as I get it back I will get after it with a vacuum gauge, relocate my vacuum takeoff at the carb base and go from there. I will keep you posted as I sort this out and let you know what I find! Thanks! Joe
I' ve been going over my brake system and this is what I have now: The biggest problem I had was not enough throw from the pedal pivot to the master cylinder rod. I extended the throw but lost some leverage up top! But before I was not moving the MC piston enough. Now If I nail the brakes it will lockup and slide, a vast improvement! I have found that my engine makes 9" of vac at idle, bring it up to 1200 rpm, it will produce 20". So now I have to decide how I want to go about producing vacuum when I'm in traffic and can't produce the RPMs' to bring up the vacuum. At least now I know I can stop but sometimes it just takes more pedal pressure! It's probably time to buy a pump, Summit has a couple self contained units made by CVR that look like an easy install!
A friend went thru the same problems after fighting all the systems flaws went from a 7" to 8" booster and can put you thru the windshield now.
Ford had a belt driven mechanical vacuum pump on it's 96/2002 Powerstroke Diesels. It isn't cheap but that might be an option. They also have an electric one that is used to run the vacuum controled A vacuum canister could be of just about any configuration you wanted it to be as long as it's sides were strong enough to hold shape with a full vacuum on it. You just need an inlet with a check valve and an outlet to connect to the brake booster.
it seems to me the problem may be with the small amount of lobe separation with that erson cam. i'm currently "de-tuning" a chevy ex-drag car that had the same problem with the brakes. it ran an erson cam with way more lift and duration and 108* lobe sep.
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