Power brake vacuum reservoir

[Greg63]

I added a power brake booster into my '63 this spring. It all works good but I can't help but think that it could be better.

I am wondering if the cam in my 327 isn't making enough vacuum to properly operate the booster (I think I am pulling less than the recommended 15") and that has led me to think I would like to try a vacuum canister as a reservoir for the times (at idle) my brakes seems hard.

Has anyone else run into this type of situation? If so, what worked for you?
Greg.

[bubba327]

Subscribed and watching.
I have the same situation but with a inline six with a cam.. I am kinda leaning toward installing the hydro-boost system from a Astro van or diesel. I have also wondered about adding a vacuum canister .

[jocko]

I believe 15" vac is about the minimum. It's worth checking to see what you've got.
Here's a prev thread on that subj: http://67-72chevytrucks.com/vboard/s...d.php?t=461940 it includes a little bit about how to measure (ported vs. non-ported vac sources) and min vac for pwr brakes.

If you've got less than 15, I'd say go manual (probably not something you want to hear) or add a vac booster. I've always wanted to avoid them if possible, just because I didn't want to mount something else under the hood of whatever it was I was working on. If only one could turn that Abraham Lincoln-tophat-lookin-heater-contraption into something more useful than, well, a heater... (I live in the desert) it might be worth keeping in there(!) But here's a thread worth reading about the vac boost before you buy: http://www.chevelles.com/forums/arch.../t-132075.html
The last post on the link has an interesting stock replacement vac boost idea.

Another option is to go with a hydroboost system like bubba mentioned - there are some threads on here - just a fwew anyway - about adding that. So if you google hydrob oost (on here) and check the "67-72 site" option, you'll probably see the handful of them pretty quickly. But I assume you are trying to use what you've got or at least determine if there is something simple being missed. Once you measure what you've got, then you can decide where to go with it.

I'm anxious to see how it all works out for you both - although I'm working on a trans swap right now, a power (4xdrum) brake upgrade with a dual mc is next. Already have the parts and Capt's bracket - but I have to admit, I'm still on the fence as to whether or not I'll actually mount the power booster or just go with the new dual mc and call it a day. One thing to consider is that depending on the booster - you can have interference with a 3 on the tree shifter ears at the end of the column. But you all already have yours mounted so must not be an issue - just posting that for other folks. Won't be an issue for me as I'm switching to a floor shifter. At least I'm trying to... Ugh! Waiting on parts as usual.

[Greg63]

Thanks for that information, Jocko.

I have read a couple of the threads you posted and that is how I got to my thread today. I read about the 15" minimum and that got me thinking.

I just tested my manifold vacuum (at the runner behind the carb, not the carb base) and I have 13" at idle and it goes up above 20" as it rev's to about 2000 rpm.

I want to try a canister and see if I can build up my vacuum (is that possible?) but I don't know what to use and am not interested in spending a lot on an experiment.
Greg.

[johan 1]

I have the same problem with me setup,am thinking do the same thing with the vacuum tank.Let us know how you make out.

[jocko]

Greg63, good question - I'd say low vacuum IS your problem - but I don't know if a canister will help you boost it at least 2" up to about 15". Unfortunately, that somewhat "negative" link I provided about vac can - nobody commented as to whether or not they re-checked their vacuum signal after they installed the vac canister, they only commented that they saw no improvement in the brakes. So, hard to tell, maybe they had wild cams and the vac can helped, but just not enough to be noticed. Also, unless you stop while holding 2000 rpm, a vac signal at 2000 rpm doesn't matter much. (by the way, that is a good little test to perform - find an empty road, get going down it at about 20-30 mph, then hold the throt so you're at about 2000 rpm - and hold that rpm while you apply brakes - that may at least give you an idea if your problem is indeed vacuum related. But it's just a test to confirm the problem - won't help much for daily use... )

Here's a link to a vac can - it will only do a better job of storing vacuum for a few more pumps of the pedal with power brake-like perf. Since you are only a few inches short, it might work. Here's the real question, do your brakes feel good on the first pump but not last to the complete stop? if that is the case, then maybe a vac canister is the answer. http://www.summitracing.com/search/?...0caniste&dds=1

if yours are not sufficient at first pump of the pedal, then you likely need a vac "pump" and those aren't cheap. they actually produce (vice just "store") vacuum.
http://www.summitracing.com/search/?...m%20pump&dds=1

Either way, here's another interesting discussion on the topic - another "dissatisfied" customer: http://www.chevelles.com/forums/arch.../t-158034.html

I think if it were me, and at first pump the pedal felt "right" but it just didn't last - and - when I tried to stop while holding the rpm up as an experiment - and the pedal felt right "longer" - then a canister may be sufficient. but remember it doesn't "make" vacuum, it only stores what you made at higher rpm while you were driving (and you said you made 20" at 2000 rpm, so I'm thinkin this may be sufficient to charge the canister up in between stops). But just like any vac storage, as soon as you start to use it, it starts to deplete - so if you pump many times in a stop, it still may go back to feeling like it is now and leave you dissatisfied. But it might be worth a try because the vac canisters aren't that expensive.

If you don't feel any improvement stopping while holding 2000 rpm - then it's probably not low vac signal that is your problem and you'd be wasting your money on either approach.

The vac pump is a more sure-fire method of ensuring a constant sufficient vacuum signal - but it's way expensive and may not be worth the effort (or more importantly the $$). But that is up to you to decide of course. Personally, if I had the same indications you had - and the same vac signals - AND it improved if I held the rpm up while I stopped - then I'd try a vac canister. If it didn't, then I'd either live with what I had or revert to non-power brakes. I personally wouldn't shell out the multi-hundred $ for a vac pump, but again, that is just me.

[Greg63]

Jocko, I am going to try some kind of reservoir to try to hold the higher vacuum (20") for that initial stopping time.
As it sits right now, the pedal feels fine at highway speeds, and it is better than adequate (whatever that means) at other times but I feel I can make it better - and trying out the reservoir won't hurt anything. If I had only 10" or so, I would probably go back to manual brakes. I am close to the minimum now and I might be able to get this to work.
The trick for me is to try to put it all together without wasting money. I have a couple of ideas and if I can get one of them to come together I will post it up here (and whether it works or not).

The bottom line for me right now is that if all this talk doesn't produce any favourable results, I am still okay with my power brakes the way they are now. It can only get better.
Greg.

[jocko]

good to go! that's a good way to approach it - hope you're able to improve it. I think a canister will help. good luck! And somewhere in your last post is the quote of the week I think..

[Greg63]

The canisters I see from Mr. Gasket and Comp cams look just like a GM a/c dryer, which I have a couple of. If I can get one of those to act as my reservoir, I might be on the cheap path before I end up buying one.

Just a thought.
Greg.

[A.T. RockDriller]

Originally Posted by Greg63

The canisters I see from Mr. Gasket and Comp cams look just like a GM a/c dryer, which I have a couple of. If I can get one of those to act as my reservoir, I might be on the cheap path before I end up buying one.

Just a thought.
Greg.

That idea sure should work for you.
All you should need is a one-way check valve between your canister and your source .....then draw from the other end of the can....
At least that's what I'm thinkin'.

[Greg63]

Well, I have been thinking on what would work, on and off, all afternoon and I came up with this.
I used some 4" pvc sewer pipe, 20" long, and two 4" pvc caps.



I cemented one cap on one end of the pipe and drilled and tapped two 1/2" pipe thread holes, side by side, on the other cap. Once the threading was done I teflon taped a pair of 1/2" x 1/4" bushings and threaded them into the cap. Then I teflon taped a pair of 1/4" x 3/8" hose barbs and installed one of them into one 1/2" bushing, and then plugged the other 1/2" bushing. I put the vacuum pump onto the hose barb and checked my work. It held vacuum for 15 minutes. I then removed the plug, installed the other hose barb and then cemented that cap on the pipe.



I hooked the assembly into the vaccum line on the truck (resting it on the inner fender) and tried it out.

When I first started the engine I found that there was no difference at idle with this plumbed into the system than without it, but when I rev'ed the engine to 2000rpm and pumped the pedal, it was soft as it was before. I let the rpm's drop back down to idle and tried the pedal again. It was softer than when I first started it up.

My guess is that this homemade reservoir is holding onto the 20" of vacuum produced when the engine is running above 2000rpm and is allowing it to be used when the engine is at idle.

I plan on painting this pipe black and mounting it to the inside of the drivers side frame rail. That is not too far from the power brakes and is out of sight.
Greg.

[jocko]

Wow. I can't wait to see your results. That some ingenuity! (I have to admit, I'd have spent the $39 at Summit....)

[Greg63]

I think I am less than $10 into this so far, but I already had the pipe.
Greg.

[Greg63]

Well, it is in and I like the results.
The reservoir is out of sight, the hose doesn't run atop the valve cover anymore, and it appears to be making a difference in the pedal effort.
I took the truck out around the block to see how the pedal felt and it was better than before.
Greg.

[Fastrucken]

Hey if you haven’t permanently hooked this up, you could hook this up with only one vacuum line attached to it. Just place a tee after a check valve and place it there. So it could go: engine, check valve, tee with one end to your reservoir and the other end of the tee to the power booster. The lack of the additional line might keep things clean under the hood and be a bit easier to plumb.

Graham

[Greg63]

Good thought.
I ran one line from the booster toward the firewall and down along the frame. The other line runs alongside it and up along the bellhousing to the back of the intake manifold.

It is actually cleaner looking now than when the hose ran from the booster to the manifold.
Greg.

[jocko]

Cool Greg! Now that's just good ol Canadian ingenuity.