Electric Vacuum Pump for Brakes?

[z boy mn]

Hey everyone, I was at a car show (the Z took first place!) yesterday and was talking to some other folks who have cars of the same vintage of mine with similar mods (Wilwood calipers, etc.). One of them was getting older and decided he wanted more brake assist, so he installed one of these:

https://www.summitracing.com/parts/sum-760152

or

https://www.amazon.com/dp/B005JV7O6S/ref=psdc_15706961_t2_B0030Z666E

Or something just like it.

He fed it into the intake manifold of his V-8 (it was a 1973 Z28 Camero) and said it made a huge difference for him. I've got the triple weber set-up, and the vacuum for my master is generated from just cylinder #6. I know it works as when I shut off the engine and brake, the pedal turns into a rock. I've also tested the one-way valve and it works fine. But...maybe more vacuum would help? I could plumb it in between the one-way valve and the master, adding vacuum to the system that way making it easier to operate the brakes, yes? Or...would it be easier/cheaper just to plumb cylinders #2 and #4 into the vacuum?

So, I'm wondering if anyone else has tried this...or if there's a difference at all. Always looking to improve the Z experience!

Edited June 11, 2017 by z boy mn

[gnosez]

Not too sure if the vac pump will make your braking effort easier but it does help if your engine doesn't produce enough vacuum.

This happens in modified engines with big cams. I ran a pump in my street car (3.2L) and in the race car (CR- 13.7:1) before replacing everything with Wilwood pedals and MCs. Much more effort involved, less weight, dial in bias adjustment and fewer parts to go wrong.

The pumps are not cheap, they are loud (how loud? You can hear them over the un-muffled race engine)) and take up a fair amount of room.

[240260280]

If you still have the small 240z brake booster, up-size to the 280z booster.  It will sort you out nicely.

 

Interesting end brace on the throttle rod.  Never saw that before!

Edited June 12, 2017 by 240260280

[z boy mn]

Thanks for the suggestions....hmmm...maybe a 280 master is the way to go. Something to try first, perhaps. The fuel pump is loud enough, I don't need another thing making noise. Also, I do have a mild cam, so another way to go is actually measure the vacuum I'm producing now to see what the base is.

As for the brace, 240260280, I noticed the rod would flex some during initial throttle-up pressure, so the brace keeps that from happening. There are probably other ways to correct it, but this one works pretty well.

[grannyknot]

I hooked up a vacuum pump off of a Volvo for my modified Z and although it works well, like gnosez says it's loud and cycles on and off everytime you hit the brakes, kinda of irritating. I'm trying to tap into the vacuum log instead.

[z boy mn]

Grannyknot, it sounds like a workable solution but maybe not something I want to do while I still have leg strength to push the pedal now. The system certainly works, but of course I'm always looking for ways to make it work better. Hmmm. Maybe I can keep an eye out on how these pumps develop and locate one in time that is quieter. The one I saw at the car show didn't make much noise, but of course it didn't operate for very long either as the car wasn't moving. It could get pretty annoying in traffic. At the same time, what do you think about adding other cylinders to the mix? It would be pretty easy to do now that I look at the manifold as each runner has a bung.

[zKars]

Unless your engine is weak in the vacuum department, there is nothing you can do improve the braking by adding more vacuum. The only real improvement will come with a larger diameter booster. You may have some fun making a later 280 booster fit. There are several steps in the evolution that involve mounting hole position changes. It can be done, just proceed carefully.

[z boy mn]

Hey zKars, I'm not sure what a weak vacuum would be or if my car is producing it...seems like a good thing to find out. I will explore the option of a bigger booster, though, as that seems like an easier/quieter route, plus a fun winter project if it includes some fabrication. I'm always up for a challenge! Have you done this procedure before? I'll see if I can find anything here on the forums to help guide me.

[gnosez]

Remove old booster which involves laying upside down while dropping the tool or tools you need in places you can't seem to reach making you crawl out of the car to find them, again. Doing it over a side impact cage bar is 10 times more of a PIA.

The 280 booster 4 bolt studs aren't in the same pattern so you will need to drill new holes and I suggest a step drill so you can make the holes one size larger to ease in the alignment of the push rod.

Because the booster is wider you might need to trim either the side of the booster or the gas pedal pin mount.

Start to finish depends on too many factors but 2-3 hours is doable as is 8.

Depending on how you intend to use your Z you could while you're at it strengthen the firewall as it will flex an easy 1/4-3/8 under heavy braking.

[z boy mn]

Wow, thanks for the tips, gnoze, I don't track the car every day, but 4-6 times a year I do get it on our local track (which is super road course) and so it does get pushed from time to time. (Interesting side note, even when I push the brakes hard on the track, they never fade or overheat. The PO installed Wilwoods on all four corners, and I'm always impressed with how they perform, even with the basic compound (B-10) pads.) I think I'd be tempted to reinforce the firewall just to be sure (and I wouldn't have thought of that!)

But, this sounds like a good winter project...I'll start poking around for a 280 brake booster. Will both a Z and a ZX boosters work eventually? There are a lot of wrecks in MN, so I don't think finding one will be that hard.

[Chickenman]

There are also auxiliary Vacuum canisters that are available for Muscle Cars with big cams and low idle vacuum. These are plumbed in parallel with the factory Booster and increase the overall Booster volume. That may be easier than changing boosters them selves. More capacity allows vacuum assist to be maximised ( volume wise ) under cruise and decel. Even changing gears will build some vacuum. Available at Summit and Jeg's. 

https://www.summitracing.com/int/search/department/brake-systems?N=4294947838&SortBy=BestKeywordMatch&SortOrder=Ascending&keyword=Vacuum Canister&retaillocation=int

Edit: This will not reduce pedal effort, but can correct issues when you run out of assist due to insufficient Booster volume. A problem that can occur early Z's and the smaller diameter Brake booster, when used for Track Days or Road Racing.

On the D-Production 240Z that I Road Raced in the late 70's, we switched over to a non-assisted Braking system and eliminated the Brake Booster entirely. This was allowed by our racing organization under Safety modifications ( ICSCC ) . On certain tracks with heavy braking ( WestWood was a prime example ) you could use up all of the booster volume under braking for a hairpin that followed a long downhill straight. Then it was a flat out climb with no braking to the next corner, Some cars could not build enough vacuum volume in the booster when changing gears. When you arrived at the next corner you found the pedal was a solid brick and you had no or little assist. Definitely a scary moment.

We eliminated the booster entirely. Had a billet adapter made to take its's place and used a Custom made adjustable length. pushrod .  We used the same pushrod mounting location on the brake pedal. This gave a very solid feel to the brakes that required a fair amount of leg strength, but were very easy to modulate. I really liked a firm hard pedal. There were a few C-Production Porsche 911's that got a Nasty surprise if they tried to out brake our D-Prod  Z at any Circuit ( Particularly WestWood ) . Of course we employed other tricks as well..... 

Edited June 18, 2017 by Chickenman

[gnosez]

you mean like this....see pics

You might find that the ZX booster is way to big and RockAuto sells reman units for cheap money.

I have the Wilwoods in the street 240 and I agree that they are really great brakes. If I wasn't wearing my harness belts I could easily break my nose on the steering wheel.

Be nice to have in the race car. In that I have the Toyo SW-12 with Z31 vented rotors and Carbotech pads. The rears are still drums (steel) with Nissan Comp shoes.